Abstract
Various strategies of plant breeding have been attempted in order to improve the ethylene resistance of flowering ornamental plants. These approaches span from conventional techniques such as simple cross-pollination to new breeding techniques which modify the plants genetically such as precise genome-editing. The main strategies target the ethylene pathway directly; others focus on changing the ethylene pathway indirectly via pathways that are known to be antagonistic to the ethylene pathway, e.g. increasing cytokinin levels. Many of the known elements of the ethylene pathway have been addressed experimentally with the aim of modulating the overall response of the plant to ethylene. Elements of the ethylene pathway that appear particularly promising in this respect include ethylene receptors as ETR1, and transcription factors such as EIN3. Both direct and indirect approaches seem to be successful, nevertheless, although genetic transformation using recombinant DNA has the ability to save much time in the breeding process, they are not readily used by breeders yet. This is primarily due to legislative issues, economic issues, difficulties of implementing this technology in some ornamental plants, as well as how these techniques are publically perceived, particularly in Europe. Recently, newer and more precise genome-editing techniques have become available and they are already being implemented in some crops. New breeding techniques may help change the current situation and pave the way toward a legal and public acceptance if products of these technologies are indistinguishable from plants obtained by conventional techniques.
Similar content being viewed by others
Introduction
The production of potted ornamental plants and cut flowers is a growing industry with annual turnover in the tens of billions of dollars,1 with the European Union being the single largest producer and consumer.2 Due to the competitive nature of the ornamental plant industry, research and development of new products and improvement of quality in existing products have become essential. The quality of flowering ornamentals, often judged by the longevity of their flowers, is an extremely important parameter in assessing quality.3 During the postharvest period, plants will likely experience stress as a result of poor lighting, temperature, and suboptimal humidity or watering.4,5 This stress often leads to visual symptoms such as wilting, color change, and abscission of various plant parts including flowers, petals, and buds. In climacteric plants, stress triggers the production of the phytohormone ethylene, which quickly deteriorates plants visually. Ethylene of exogenous origin can also affect the plants in closed spaces6 and plants that have been exposed to ethylene will often no longer be sellable.
In recent years, the biological significance of ethylene in ornamental production, its signaling pathway within the plant, and methods to alleviate its consequence to the aesthetic value of ornamental plants have been extensively reviewed.7–13 However, many reviews only consider a limited number of plant species, or focus on a particular perspective for solving the problem in only one or two of the levels of the ethylene pathway. In order to acquire an overview of the problems associated with ethylene-induced quality losses in ornamental plant production, recent research and advances in the field of ethylene biology and breeding techniques must be considered. The present review aims to compare results from past approaches in order to discuss future breeding strategies. It will also point out avenues not yet explored in the area of ornamental plant breeding which may be essential for reducing ethylene responses that remains a decisive factor for high-quality production of many ornamental plants.
Regulation of the ethylene pathway
The ethylene biosynthesis and signaling pathway can be presented in a linear model (Figure 1). Ethylene is essential for many processes in the plant and thus, there is a constant, low ethylene production (Figure 1a).14 Under certain conditions, however, ethylene biosynthesis and sensitivity increase in specific tissues and this triggers the ethylene signaling pathway (Figure 1b).15 This initially starts as an increase in expression of some of the enzymes responsible for ethylene biosynthesis16–18 which leads to higher ethylene production19 that may amplify itself in an autocatalytic fashion in some cases.20
Simplified ethylene pathway. (a) Basal production of ethylene in the flowers during development before senescence. (b) The ethylene pathway upon triggering. The stimulus is translated to elevated ethylene synthesis producing higher levels of ethylene which inactivates the receptors initiating the signaling cascade which changes gene expression and finally induces physiological processes in the flower which may include the initiation of an autocatalytic loop.14 (c) Simplified molecular events of the ethylene pathway. Methionine is enzymatically converted to S-adenosyl-l-methionine (SAM) by SAM synthase (SAS). SAM is partially converted back to methionine via several steps, but it also produces 1-aminocyclopropane-1-carboxylic acid (ACC) by ACC synthase (ACS). ACC is transformed to ethylene by ACC oxidase (ACO). Ethylene binds to receptors and stops their signal to CONSTITUTIVE TRIPLE RESPONSE1 (CTR1), which then stops its suppressing signal to ETHYLENE INSENSITIVE2 (EIN2). The released EIN2 is then cleaved and part of it is transported into the nucleus where activation of the ETHYLENE INSENSITIVE3/ETHYLENE INSENSITIVE3-LIKE (EIN3/EIL) transcription factor family occurs. This initiates a transcription cascade by activation of ETHYLENE RESPONSE FACTORs (ERFs) which eventually leads to differential gene expression and a physiological response.15
Recently, it was shown that different ACS homologs of Dianthus caryophyllus18 and Dianthus superbus21 were expressed in association with either the basal or the climacteric phase. In Petunia22 and Paeonia suffruticosa,23 the same was observed for certain ACS and ACO homologs. It therefore seems that these enzymes, central for ethylene biosynthesis (Figure 1), may hold the key for the ability of the plant to transition from basal to climacteric ethylene production (Figure 1).24 Furthermore in Arabidopsis, ACS activity was demonstrated to be affected by the formation of hetero- and homo-dimers,24,25 and phosphorylation by the mitogen-activated protein kinase (MAPK) MPK6, which itself is expressed in response to stress.26 Recently, a similar role for MPK6 was demonstrated in Rosa hybrida.27
The function of ethylene receptors too, is subject to modification from various proteins such as RESPONSIVE TO ANTAGONIST1 (RAN1),28,29 REVERSION TO ETHYLENE SENSITIVITY1 (RTE1),30–32 and their own histidine autokinase activity.33 Receptors often act simultaneously, and in physical association with each other,34,35 but as with the ethylene biosynthesis enzymes, different receptor homologs are expressed depending on the developmental stage of the flower, as has been documented in D. caryophyllus36, R. hybrida,37 Oncidium,38 Delphinium,39 and Pelargonium hortonum.40
The function of EIN2 can be inhibited not only by CTR1 but also ETHYLENE RESISTANT/ETHYLENE RECEPTOR1 (ETR1)41 and EIN2 TARGETING PROTEIN1 (ETP1) and ETP2. ETP1 and ETP2 were down-regulated in the presence of ethylene,42,43 but activated CTR1 in the absence of ethylene.44 Unlike most of the other genes of the ethylene pathway, EIN2 has no homologs and no functional overlap with other genes.45–47 There is some indication that EIN2 expression is influenced by auxin and abscisic acid (ABA),48 which means that EIN2 could be a point of crosstalk for several different pathways. Interestingly, increase in EIN2 protein levels has been shown to be concomitant with expression of the transcription factor ORESARA1 (ORE1) in Arabidopsis, associated with age-induced programmed cell death. ORE1 is suppressed by miRNA164, which declines with cell age.49 In R. hybrida flowers exposed to ethylene, different miRNAs including miRNA164, exhibited a change in expression level in petals,50 indicating a possible new level for expression control of ethylene genes.
EIN3/EIL homologs also change in the transition of the plant tissue to the climacteric phase. In D. caryophyllus, DcEIL3 increased51 and DcEIL1 decreased52 in expression as flower development occurred. Tanase et al.53 on the other hand documented that DcEIL3 expression did not change with age in petals, but DcEIL4 was expressed less in older flowers. In P. suffruticosa, PsEIL1 accumulated from the flower opening stage to senescence, while PsEIL2 and PsEIL3 decreased after flower opening.54 PsEIL2 and PsEIL3 mRNA levels increased in response to exogenous ethylene, while PsEIL1 was unaffected by this treatment and plants treated with 1-methylcyclopropene (1-MCP) and exposed to ethylene, exhibited a decrease in PsEIL3 expression.54 In Oncidium gardneri, OgEIL1 and OgEIL2 were constitutively expressed in flower buds, but when the buds were exposed to ethylene, OgEIL1 clearly peaked in expression relative to OgEIL2.55 Collectively, these genes present numerous targets for modifying ethylene regulation molecularly.
Reducing ethylene-promoted senescence
Approaches addressing the problem of ethylene-induced senescence can be broadly divided into two main groups: interventions directly addressing the ethylene pathway and those indirectly targeting it as described below. Because the ethylene pathway is fundamentally integrated into plant metabolism, changing a seemingly unrelated pathway of the plant can result in some effect on the ethylene pathway. Techniques to combat senescence such as changes in the gas composition of the atmosphere or temperature of storage places for plants have also been examined and gave mixed results.56–58 These techniques, although successful to a point, lead to unsustainable production of ornamental plants because they extend the time needed for production and cost in terms of consumption of electricity, water, personnel, and specialized equipment. Silver thiosulfate (STS) and 1-MCP have been proven to be powerful inhibitors of ethylene responses and STS is commonly used in ornamental plant production. However, silver is harmful to humans and the environment and thus its use should be avoided. Plant breeding on the other hand strives to improve the intrinsic quality of ornamental plants and thereby produce sustainable products.59
Targeting the ethylene pathway directly
Cross-pollination coupled with ethylene screening
The simple strategy of choosing individuals in a population that display superior flower ethylene tolerance and crossing these individuals with each other, will result in progeny with a lower ethylene sensitivity than the original population, if the trait is heritable.60 Success in such breeding has been reported in Begonia61 and D. caryophyllus.62 It has long been known that there are vast differences among cultivars of D. caryophyllus in their ethylene biosynthetic ability and affinities of receptors to ethylene.63 By using only simple pollination, Onozaki and coworkers62 achieved a significant improvement in the longevity of D. caryophyllus flowers from 1992 to 2004. Their original material had flower longevity of 5.7 days,64,65 but through repeated crossing, the sixth generation had increased its mean of flower life to 15.9 days.62 An investigation into the cause of this increase, revealed that the ethylene biosynthesis enzyme genes DcACS1, DcACS2, and DcACO1 were all expressed in extremely low levels in cultivars with a good longevity and ethylene production was as low.66,67
This approach involves screening for ethylene insensitivity and will only be applicable if a population exhibits significant differences in response between individuals. The number of ornamental flower cultures showing such diversity is, however, very large. Differences in longevity of flowers have been noted for Paeonia,68 Delospermum, Campanula, Sedum, Cephalaria, Lobelia, Armeria, Primula, Penstemon,69 Lisianthus, Trachelium, Zinnia,70 Potentilla, Lysimachia, Veronica, Chelone,71 and Rosa11,72,73 which also exhibited varying ethylene production levels.73–76 Similar observations has been made for Pelargonium,77 where heritability has also been documented,78 as it has been for Impatiens walleriana,79 Antirrhinum majus,80–82 Dianthus barbatus,83 and Petunia.84 In many ornamental plant genera, cultivar-specific variation in ethylene sensitivity has been demonstrated including Phalaenopsis85,86 and Kalanchoë.87
Hybridization
Many of the abovementioned genera are typically represented by hybrids in ornamental plant production. Hybridization is achieved by interspecific cross-pollination and it thus produces extremely heterogeneous progeny, which may be good for producing cultivars with higher ethylene tolerance. A well-documented example of this is found in Australian waxflower breeding where Chamelaucium species were hybridized with Verticordia plumosa, forming more ethylene-insensitive plants.88 Hybrids of Leptospermum species89 and Grevillea90 similarly have been reported to have longer longevity than the parental species, which may be correlated with higher ethylene tolerance as both genera are climacteric. This aspect, however, has not yet been investigated.
The major disadvantage of both intra- and interspecific cross-pollination is that it cannot be used directly for improving existing cultivars. Considerable back-crossing to the original plant may be necessary.91 This problem can be solved to some extent by employing marker-assisted selection, if reliable markers are found92 and have been used successfully in ornamentals such as D. caryophyllus with regards to bacterial wilt resistance.93 Hybridization can be more demanding as manipulation of the style as well as embryo rescue or ovule and ovary culture may be necessary in order to yield any progeny, as exemplified in Kalanchoë species hybridization.94
Conventional mutagenesis
Techniques that increase genetic variability where no natural variation exists are found in conventional breeding with the use of mutagenic chemicals or radiation.95 Such breeding strives to change the cultivar in a certain qualitative aspect and leaves its agronomical traits unchanged, making it easier for producers to handle, and saves time that would otherwise be spent on back-crossing.71,96 However, as it is impossible to control where the mutation occurs in the genome, many plants will have to be screened before a plant exhibiting any change in the relevant trait is found.97 Targeting Induced Local Lesions In Genomes (TILLING) can be used to save time that would otherwise be needed for phenotyping the plants and has been used successfully in the field of ethylene-response improvement. Dahmani-Mardas et al.98 produced Cucumis melo with a knockout mutation in the CmACO1 gene which displayed a longer shelf life and better firmness than none-mutated plants. TILLING is readily applicable to ornamental plants as is exemplified in Petunia.99
Genetic transformation
Genetic transformation is the transfer of foreign or native genes and promoters to a target genome by Agrobacterium-mediated transformation, particle bombardment, or infiltration. Agrobacterium tumefaciens-mediated transformation with recombinant DNA has been used in various ways to modify ethylene biosynthesis and signaling. These approaches have improved understanding of ethylene biosynthesis and signaling; however, their use in commercial breeding is limited and this technique’s products are considered genetically modified.59,100
Antisense or sense transformations of ACS and ACO genes have been successfully attempted in various ornamental species including D. caryophyllus,101–113 Torenia,104 Petunia,22,105 and Begonia.60,106 All transformed plants exhibited longer shelf life, presumably due to lower production of ethylene. Klee et al.107 conducted an alternative modification of the biosynthesis pathway with the removal of ACC by the addition of the enzyme ACC deaminase, found in bacteria, to Solanum lycopersicum which significantly delayed ripening of the fruit. However, even though plants with lower ethylene production have a longer flower life, their quality can still be negatively affected by exogenous ethylene.
Transformations of Petunia with the Atert1-1 mutated gene from Arabidopsis using CaMV 35S constitutive promoter, resulted in plants with considerably higher ethylene tolerance but also with severely hampered growth.108 Succeeding studies used a flower-specific FBP1 promoter in Kalanchoë,109 Campanula,110,111 and D. caryophyllus,112,113 which provided a better flower longevity without other developmental effects, since the promoter ensured expression solely in flowers. Transformations of mutated genes other than Atetr1-1 have also been studied in Nemesia strumosa114 and Torenia fournieri. In both cases, ethylene insensitivity was increased, but not as much as with Atert1-1 (Table 1).8
Other promoters such as FBP3,115 PSAG-12,116 FS19, and FS268 that are solely associated with flower tissue, also have potential to be used in this context and other promoters are still being investigated.117 Chemically inducible promotor systems are also within the reach of today’s technology, and are exemplified by the DEX-inducible system, demonstrated in Petunia hybrida118 (Table 1), and more famously, the ethanol-inducible system119 which has been successfully used in different crops.120 Inducible systems seem not to affect the plant adversely,121 but the inducing chemical still needs to be applied to the plant in due time, which makes such a system commercially less appealing.
Great care needs to be exercised when choosing a promoter, as a study by Cobb et al.122 demonstrated that Petunia transformed with Atetr1-1 did not have delay in senescence under the flower-specific APETALA3 (AP3) promoter, as this promoter only drives expression in buds and young flowers, but not in mature flowers (Table 1).
Overexpressing PhEIN2 in Petunia using the CaMV 35S promoter has also been attempted. This produced plants with significant delays in petal senescence in response to exogenous ethylene or pollination, as well as inhibited root development and a shorter life span.126 When this silencing transformation was combined with the Atetr1-1 mutation, ethylene was inhibited even more,127 demonstrating the possibility of increasing insensitivity by stacking transformations of several components simultaneously.
Petunia plants transformed with a sense PhEIN3 exhibited delayed petal senescence, but no increase of flower longevity,8,127 which may possibly be due to the redundancy found among EIN3/EIL members. S. lycopersicum was transformed with a construct silencing EIN3 BINDING F-BOX1 (EBF1) and EBF2, which rapidly target EIN3/EILs for degradation that significantly increased the rate of senescence in S. lycopersicum.45 This presents an opportunity for future research, potentially by overexpression of EBFs.
ERFs are a sizable and diverse group of genes, many of which are up-regulated in response to ethylene, but have largely been overlooked by researchers so far. Chang et al.128 observed that by silencing the ERF Petunia transcription factor homeodomain-leucine zipper protein (PhHDZip), PhACS and PhACO were decreased in expression in transformed flowers and led to an increase of flower longevity by 20%.
Genome-editing technologies
During the last decades, several innovative biotechnologies have been developed which appear to have potential in breeding toward ethylene tolerance.100,129,130 These technologies are based on engineered nucleases that cleave DNA in a sequence-specific manner, thus enabling targeted genome-editing. Modifying or inactivating specific gene function is possible due to sequence-specific DNA binding domains or RNA sequences. The oldest of these techniques is zinc finger nucleases (ZNFs), which relies on an engineered endonucleases that are able to attach to a specific target sequence and induce a double-strand break. This is perceived by the cell, which repairs the break by mechanisms which may cause sequence alterations or introduce small templates.131,132 A newer alternative to ZNFs is transcription activator-like effector nucleases (TALENs), which functions in much the same manner as ZNFs. Recently, however, the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein9 (CRISPR/Cas9) system has been developed. The CRISPR/Cas9 system functions via a mechanism similar to RNA interference, which can recognize and cleave foreign DNA.100 Both TALEN and CRISP/Cas9 have been demonstrated to be functional for targeted mutagenesis in S. lycopersicum,133,134 however, no modifications of the ethylene pathway have yet been conducted. It is important to mention that all these methods rely on a technology in order to deliver the construct to the genome of the plant, and are therefore still limited to plants where a genetic transformation, regeneration or virus-based delivery system is reliable. In order to bypass negative effects on growth of plants due to defective ethylene signaling, the genes that should be targeted are those which have homologs that are clearly associated with the climacteric phase. Using this approach, the pathway should function normally under growth and development. Therefore, certain homologs of ACS, ACO, ethylene receptors, and EIN3/EIL may present good targets for knockouts.
Targeting the ethylene pathway indirectly
Hormonal interaction
Application of cytokinins such as kinetin and zeatin to petals of D. caryophyllus delayed the conversion of ACC to ethylene.135 Cytokinin oxidase/dehydrogenase, responsible for cytokinin degradation, was up-regulated during senescence in D. caryophyllus136 and Petunia,137 and when it was inhibited in D. caryophyllus petals, the senescence phase was prevented.138 This knowledge has been applied by transformations with isopentenyl transferase, important for the synthesis of many cytokinins, under the control of senescence-associated promoter PSAG12. Transformed Petunia plants exhibited elevated levels of cytokinins in flowers and significant delay in senescence and ethylene production as well as higher tolerance for exogenous ethylene.139 Similarly in Rosa, ethylene sensitivity decreased in leaves, but flowers were not studied.140
Exogenous application of hormones and other substances have also been shown to decrease the expression of genes of the ethylene pathway including ABA, which inhibited ACS and ACO in Hibiscus141 and D. caryophyllus.142 Moreover, nitric oxide down-regulated the activity of RhACO and lowered the production of ethylene resulting in longer shelf life of R. hybrida flowers143 and glucose down-regulated PsACS1 in P. suffruticosa flowers.144 Other sugars have also been shown to increase flower longevity.136,145–148 These studies demonstrate that there is a vast potential in exploring new ways to achieve products of higher quality.
Senescence-related and non-ethylene pathway genes
Exploration of different genes which is seemingly not connected to the ethylene pathway has also been pursued. There are three main strategies in this area. The first is identification of genes that are highly expressed in young tissue but not during senescence, and constitutively overexpressing those. The second approach goes the other way and starts with the identification of genes highly expressed in senescing tissue, and silencing their expression. The third tactic is targeting protein synthesis.
The first strategy can be exemplified by the gene FOREVER YOUNG FLOWER (FYF) from Arabidopsis, which was highly expressed in young flowers but not in old flowers. Transformation using this gene under constitutive expression in S. lycopersicum resulted in down-regulation of various ACS and ACO homologs. The same transformation in Eustoma grandiflorum caused a delay in senescence and down-regulation of ERFs.149 Furthermore, when combined with etr1, ein2, or ctr1 mutations, it further enhanced flower longevity in Arabidopsis.149
Investigating a MADS-domain transcriptional regulator, AGAMOUS-LIKE-15 (AGL15), Fernandez et al.150 noted its accumulation in young tissue and developing organs. Constitutive overexpression of AGL15 increased the longevity of petals significantly in Arabidopsis151 and caused a repression of GmACO1 in Glycine max.152 It is now established that AGL15 has similar activity as AGL18, both serving as repressors of early flowering and in this way leading to better longevity if still expressed when flowering does occur.153 Another MADS-domain transcriptional regulator that has been recognized to be associated with young flowers of Phalaenopsis equestris is PeMADS6. Arabidopsis plants transformed with a construct overexpressing PeMADS6 exhibited flower longevity up to four times longer than wild type plants.154
Examples from the second strategy of silencing senescence-related genes, include ACTIN-RELATED PROTEIN 4 (ARP4), a chromatin modification gene, that has been silenced using RNAi in Arabidopsis,155 which resulted in longer flower life. The gene MjXB3, coding for a RING zinc finger ankyrin repeat protein, has been demonstrated to be highly expressed in senescing flowers of Mirabilis jalapa, P. hybrida, and D. caryophyllus. Using virus-induced gene silencing for MjXB3 in P. hybrida, Xu et al.156 demonstrated that flower longevity was extended by two days, corresponding to a 20% increase compared to wild type flowers.
The third strategy of targeting protein synthesis owes its inspiration to ethylene-insensitive flowers,13 where complete inhibition of protein synthesis in flowers increases flower longevity.157 The relevance of this to climacteric flowers has been attested by silencing PBB2 (coding for the beta subunit of the 26S proteasome) using an inducible system in Petunia.158 Mature cut flowers that were induced lasted considerably longer than uninduced flowers. Reid and Jiang13 demonstrated the same concept by silencing one of the ribosomal subunit genes (RPL2), again using an inducible system. Once more, the longevity of cut Petunia flowers placed in water with the inducing agent was much better than those uninduced. This approach, however, still relies on the application of an inducer, and is not realistic for use in commercial potted-plant production. For the cut-flower industry, however, there may be great potential.
Natural transformation
Transformation with the naturally occurring soil bacterium Agrobacterium rhizogenes has been termed natural transformation159 due to the fact that no recombinant DNA is used and the infection is a natural process. Authorities in Denmark have confirmed that naturally transformed plants are not covered by the GMO legislation in Europe.59 Using a wild strain of A. rhizogenes, Lütken et al.59,160 transformed Kalanchoë plants and observed that plants which contained rol-genes from A. rhizogenes exhibited significantly increased postharvest quality,159 an ability which was maintained through two generations along with the rol-genes.161 The mechanism behind this response is yet unknown and many open reading frames of the plasmids in question still remain uninvestigated. Changes in longevity of flowers transformed with rol-genes may be due to altered hormone homeostasis and/or sugar metabolism and transport.159
Discussion
Strategies targeting the ethylene pathway indirectly seem to be as effective as those which target it directly. Of the indirect strategies, ectopic overexpression of genes associated with juvenile tissue, such as FYF or AGL15, seems to be particularly promising, as is the prospect of overproduction of hormones that are antagonistic to ethylene, such as cytokinins and ABA. Strategies that focus on the ethylene pathway directly have been more numerous and have targeted nearly all known elements of the ethylene pathway. Research comprising flower-specific promotor sequences in genetic transformations seems to be especially propitious in providing the ability to express the transferred gene only in flowers or even more specifically, only in senescing flowers. Silencing several genes simultaneously in the flowers of plants as in Petunia,119 may be the ultimate answer, and is a feature that is well within the grasp of current technology and methodology. Various combinations of overexpression of certain genes associated with development and silencing genes associated with senescence may very well be a worthwhile strategy as well.
It is remarkable that both conventional techniques such as simple cross-pollination and genetic transformation using recombinant DNA succeeded in breeding ornamental plants which have higher tolerance for ethylene and thus higher intrinsic quality. Agrobacterium-mediated transformation, where reliable, has the advantage that breeding can be much faster when transferring specific target genes. Breeding based on genetic transformation is more precise and can easily cross incompatibility boundaries in comparison with conventional crossing.91 This is a particularly important advantage in ornamental plants that have long development cycles such as orchids,162 however, in fast growing plants, this advantage is less substantial.60
Although conventional and genetic transformation are not mutually exclusive, the fact remains that ornamental plant products that are genetically modified are conspicuously missing on the market, especially in Europe, with only a handful of products sold worldwide.163 The basic reason for this is the status of such product as genetically modified organisms (GMOs). Europe, the biggest consumer, producer and breeder of ornamentals has some of the most comprehensive and strict legislation concerning GMOs.1 At the moment, the approval of GMO products is conducted on a case-by-case basis and is both expensive and time-consuming.164 Moreover, the technology and training required for producing GMOs are themselves expensive, which brings a substantial economic burden.60 Producers not operating in Europe also face difficulties as GMO legislation may be quite different from country to country.165 However, the emergence of new genome-editing techniques presents new challenges particularly for European legislation in the area of GMOs, which could lead the way to broader acceptance of new breeding techniques and their products.
Techniques such as ZFN, TALENs, and CRISPR/Cas9 that can be used to achieve precise mutagenesis and silencing or overexpressing genes are now readily available, and can be used in such a way that does not introduce foreign elements to the genome of the final product.127,166 The question of whether the products of these techniques are considered GMOs or not has not yet been settled, and jurisdictions that consider the methods alone rather than the actual properties of the final plant product may end up with ineffective legislation that cannot be enforced, as pointed out in Seeds of Change.167 Certainly such techniques have the ability to greatly reduce the time, and thus the bulk of the cost which is associated with plant breeding. The first commercially available plant derived from a genome-editing technique, a herbicide-resistant oilseed rape, has already been announced.168 There are still technical difficulties associated with the actual transformation step for many ornamental plants, which can only be overcome by further research. For this reason, it is must be of the utmost importance for any plant breeding company to devote some of its resources to research in such new breeding techniques.
Conclusions
Strategies targeting the ethylene pathway directly seem to have as much potential as those targeting indirect components, and very diverse species of ornamental plants suggest great potential in ethylene tolerance breeding. Although conventional breeding techniques are slower than newer breeding techniques, they remain the most used in ornamental plant breeding for higher ethylene tolerance. This is most probably due to the legal status of genetic modification approaches. However, as newer precise genome-editing techniques become available, it is very likely that the products of such techniques will be accepted worldwide. The reason for this is that such plants would be indistinguishable from plants derived by the use of conventional breeding techniques. It is therefore recommendable for ornamental plant breeders to begin the implementation of such new breeding technologies, as they have great to potential to lead to superior plant products needed by the ornamental plant industry.
References
Chandler SF, Brugliera F . Genetic modification in floriculture. Biotechnol Lett 2011; 33: 207–214.
European Commission Agriculture and Rural Development. Statistics for live plants and products of floriculture, 2013. Available at http://ec.europa.eu/agriculture/fruit-and-vegetables/product-reports/flowers/index_en.htm (accessed 1 March 2014).
Palma M, Hall C, Collart A . Repeat buying behavior for ornamental plants: A consumer profile. JFDRS 2011; 42: 67–77.
Wagstaff C, Bramke I, Breeze E, Thornber S, Harrison E et al. A specific group of genes respond to cold dehydration stress in cut Alstroemeria flowers whereas ambient dehydration stress accelerates developmental senescence expression patterns. J Exp Bot 2010; 61: 2905–2921.
Müller R, Sisler EC, Serek M . Stress induced ethylene production, ethylene binding and the response to the ethylene action inhibitor (1-MCP) in miniature roses. Sci Hortic 1999; 83: 51–59.
Morgan PW . Another look at interpreting research to manage the effects of ethylene in ambient air. Crop Sci 2011; 51: 903–913.
Shibuya K . Molecular mechanisms of petal senescence in ornamental plants. J Jpn Soc Hortic Sci 2012; 81: 140–149.
Satoh S . Ethylene production and petal wilting during senescence of cut carnation (Dianthus caryophyllus) flowers and prolonging their vase life by genetic transformation. J Jpn Soc Hortic Sci 2011; 80: 127–135.
Fischer AM . The complex regulation of senescence. Crit Rev Plant Sci 2012; 31: 124–147.
Schaller GE . Ethylene and the regulation of plant development. BMC Biol 2012; 10: 9.
Fanourakis D, Pieruschka R, Savvides A, Macnishd AJ, Sarlikioti V et al. Sources of vase life variation in cut roses: A review. Postharvest Biol Technol 2013; 78: 1–15.
Merchante C, Alonso JM, Stepanova AN . Ethylene signaling: Simple ligand, complex regulation. Curr Opin Plant Biol 2013; 16: 554–560.
Reid MS, Jiang C . Postharvest biology and technology of cut flowers and potted plants. In: Janek J (ed.) Horticultural reviews 2012; Vol. 40. 1st ed. Hoboken, NJ: John Wiley & Sons, 1–54.
Paul V, Pandey R, Srivastava GC . The fading distinctions between classical patterns of ripening in climacteric and non-climacteric fruit and the ubiquity of ethylene—an overview. J Food Sci Technol 2012; 49: 1–21.
Lin Z, Zhong S, Grierson D . Recent advances in ethylene research. J Exp Bot 2009; 60: 3311–3336.
Woodson WR, Park KY, Drory A, Larsen PB, Wang H . Expression of ethylene biosynthetic pathway transcripts in senescing carnation flowers. Plant Physiol 1992; 99: 526–532.
ten Have A, Woltering EJ . Ethylene biosynthetic genes are differentially expressed during carnation (Dianthus caryophyllus L.) flower senescence. Plant Mol Biol 1997; 34: 89–97.
In BC, Strable J, Binder BM, Falbel TG, Patterson SE . Morphological and molecular characterization of ethylene binding inhibition in carnations. Postharvest Biol Technol 2013; 86: 272–279.
Ma N, Tan H, Liu XH, Xue JQ, Li YH et al. Transcriptional regulation of ethylene receptor and CTR genes involved in ethylene-induced flower opening in cut rose (Rosa hybrida) cv. Samantha. J Exp Bot 2006; 57: 2763–2773.
Kende H . Ethylene biosynthesis. Annu Rev Plant Physiol Plant Mol Biol 1993; 44: 283–307.
Harada T, Murakoshi Y, Torii Y, Tanase K, Onozaki T et al. Analysis of genomic DNA ofDcACS1, a 1-aminocyclopropane-1-carboxylate synthase gene, expressed in senescing petals of carnation (Dianthus caryophyllus) and its orthologous genes in D. superbus var. longicalycinus. Plant Cell 2011; 30: 519–527.
Huang LC, Lai UL, Yang SF, Chu MJ, Kuo CI et al. Delayed flower senescence of Petunia hybrida plants transformed with antisense broccoli ACC synthase and ACC oxidase genes. Postharvest Biol Technol 2007; 46: 47–53.
Zhou L, Zhang C, Fu J, Liu M, Zhang Y et al. Molecular characterization and expression of ethylene biosynthetic genes during cut flower development in tree peony (Paeonia suffruticosa) in response to ethylene and functional analysis of PsACS1 in Arabidopsis thaliana. J Plant Growth Regul 2013; 32: 362–375.
Tsuchisaka A, Yu G, Jin H, Alonso JM, Ecker JR et al. A combinatorial interplay among the 1-Aminocyclopropane-1-Carboxylate Isoforms regulates ethylene biosynthesis in Arabidopsis thaliana. Genetics 2009; 183: 979–1003.
Wang KLC, Li H, Ecker JR . Ethylene biosynthesis and signaling networks. Plant Cell 2002; 14: 131–151.
Liu Y, Zhang S . Phosphorylation of 1-aminocyclopropane-1-carboxylic acid synthase by MPK6, a stress-responsive mitogen-activated protein kinase, induces ethylene biosynthesis in Arabidopsis. Plant Cell 2004; 16: 3386–3399.
Meng Y, Ma N, Zhang Q, You Q, Li N et al. Precise spatio-temporal modulation of ACC synthase by MPK6 cascade mediates the response of rose flowers to rehydration. Plant J 2014; 79: 941–950.
Hirayama T, Kieber JJ, Hirayama N, Kogan M, Guzman P et al. RESPONSIVE-TO-ANTAGONIST1, a Menkes/Wilson disease–related copper transporter, is required for ethylene signaling in Arabidopsis. The Cell 1999; 97: 383–393.
Binder BM, Rodríguez FI, Bleecker AB . The copper transporter RAN1 is essential for biogenesis of ethylene receptors in Arabidopsis. J Biol Chem 2010; 285: 37263–37270.
Qiu L, Xie F, Yu J, Wen CK . Arabidopsis RTE1 is Essential to Ethylene Receptor ETR1 Amino-terminal signaling independent of CTR1. Plant Physiol 2012; 159: 1263–1276.
Yu Y, Wang H, Liu J, Fu Z, Wang J et al. Transcriptional regulation of two RTE-like genes of carnation during flower senescence and upon ethylene exposure, wounding treatment and sucrose supply. Plant Biol 2011; 13: 719–724.
Ma Q, Du W, Brandizzi F, Giovannoni JJ, Barry CS . Differential control of ethylene responses by GREEN-RIPE and GREEN-RIPE-LIKE1 provides evidence for distinct ethylene signaling modules in tomato. Plant Physiol 2012; 160: 1968–1984.
Hall BP, Shakeel SN, Amir M, Ul Haq N, Qu X et al. Histidine kinase activity of the ethylene receptor ETR1 facilitates the ethylene response in Arabidopsis. Plant Physiol 2012; 159: 682–695.
Grefen C, Städele K, Ruzicka K, Obrdlik P, Harter K et al. Subcellular localization and in vivo interactions of the Arabidopsis thaliana ethylene receptor family members. Mol Plant 2008; 1: 308–320.
Gao Z, Wen CK, Binder BM, Chen YF, Chang J et al. Arabidopsis receptors mediate signaling in heteromeric interactions among ethylene. J Biol Chem 2008; 283: 23801–23810.
Shibuya K, Nagata M, Tanikawa N, Yoshioka T, Hashiba T et al. Comparison of mRNA levels of three ethylene receptors in senescing flowers of carnation (Dianthus caryphyllus L.). J Exp Bot 2002; 53: 399–406.
Müller R, Stummann BM, Serek M . Characterization of an ethylene receptor family with differential expression in rose (Rosa hybrida L.) flowers. Plant Cell Rep 2000; 19: 1232–1239.
Huang WF, Huang PL, Do YY . Ethylene receptor transcript accumulation patterns during flower senescence in Oncidium ‘Gower Ramsey’ as affected by exogenous ethylene and pollinia cap dislodgement. Postharvest Biol Technol 2007; 44: 97–94.
Tanase K, Ichimura K . Expression of ethylene receptors Dl-ERS1-3 and Dl-ERS2, and ethylene response during flower senescence in Delphinium. J Plant Physiol 2006; 163: 1159–1166.
Dervinis C, Clark DG, Barrett JE, Nell TE . Effect of pollination and exogenous ethylene on accumulation of ETR1 homologue transcripts during flower petal abscission in geranium (Pelargonium hortorum L. H. Bailey). Plant Mol Biol 2000; 42: 847–856.
Bisson MMA, Groth G . New insight in ethylene signaling: autokinase activity of ETR1 modulates the interaction of receptors and EIN2. Mol Plant 2010; 5: 882–889.
Qiao H, Chang KN, Yazaki JH, Ecker JR . Interplay between ethylene, ETP1/ETP2 F-box proteins, and degradation of EIN2 triggers ethylene responses in Arabidopsis. Genes Dev 2009; 23: 512–521.
Bisson MMA, Groth G . Cyanide is an adequate agonist of the plant hormone ethylene for studying signaling of sensor kinase ETR1 at the molecular level. Biochem J 2012; 444: 261–267.
Shahri W, Tahir I . Flower senescence: Some molecular aspects. Planta 2014; 239: 277–297.
Yang TF, Gonzalez-Carranza ZH, Maunders MJ, Roberts JEA . Ethylene and the regulation of senescence processes in transgenic Nicotiana sylvestris Plants. Ann Bot 2008; 101: 301–310.
Yang Y, Wu Y, Pirrello J, Regad F, Bouzayen M et al. Silencing Sl-EBF1 and Sl-EBF2 expression causes constitutive ethylene response phenotype, accelerated plant senescence, and fruit ripening in tomato. J Exp Bot 2010; 61: 697–708.
Fu Z, Wang H, Liu J, Liu J, Wang J et al. Cloning and characterization of a DCEIN2 gene responsive to ethylene and sucrose in cut flower carnation. Plant Cell Tissue Organ Cult 2011; 105: 447–455.
Gao F, Hao J, Yao Y, Wang X, Hasi A . Cloning and characterization of ethylene-insensitive 2 (EIN2) Gene from Cucumis melo. Rus J Plant Physiol 2013; 60: 713–719.
Kim JH, Woo HR, Kim J, Lim PO, Lee IC et al. Trifurcate feed-forward regulation of age-dependent cell death involving miR164 in Arabidopsis. Science 2009; 323: 1053–1057.
Pei H, Ma N, Chen J, Zheng Y, Tian J et al. Integrative analysis of miRNA and mRNA profiles in response to ethylene in rose petals during flower opening. PLoS One 2013; 8: e64290.
Iordachescu M, Verlinden S . Transcriptional regulation of three EIN3-like genes of carnation (Dianthus caryophyllus L. cv. Improved White Sim) during flower development and upon wounding, pollination, and ethylene exposure. J Exp Bot 2005; 1: 2011–2018.
Waki K, Shibuya K, Yoshioka T, Hashiba T, Satoh S . Cloning of a cDNA encoding EIN3-like protein DC-EIL1 and decrease in its mRNA level during senescence in carnation flower tissues. J Exp Bot 2001; 52: 377–379.
Tanase K, Aida R, Yamaguchi H, Tanikawa N, Nagata M et al. Heterologous expression of a mutated carnation ethylene receptor gene, Dc-ETR1, suppresses petal abscission and autocatalytic ethylene production in transgenic Torenia fournieri Lind. J Jpn Soc Hortic Sci 2011; 80: 113–120.
Wang Y, Zhang C, Peiyi J, Wang X, Wang W et al. Isolation and expression analysis of three EIN3-like genes in tree peony (Paeonia suffruticosa). Plant Cell 2013; 112: 181–190.
Chen SY, Tsai HC, Raghu R, Do YY, Huang PL . cDNA cloning and functional characterization of ETHYLENE INSENSITIVE3 orthologs from Oncidium Gower Ramsey involved in flower cutting and pollinia cap dislodgement. Plant Physiol Biochem 2011; 49: 1209–1219.
Serek M, Woltering EJ, Sisler EC, Frello S, Sriskandarajah S . Controlling ethylene responses in flowers at the receptor level. Biotechnol Adv 2006; 24: 368–381.
Yangkhamman P, Tanase K, Ichimura K, Fukai S . Depression of enzyme activities and gene expression of ACC synthase and ACC oxidase in cut carnation flowers under high-temperature conditions. Plant Growth Regul 2007; 53: 155–162.
Kou L, Turner ER, Luo Y . Extending the shelf life of edible flowers with controlled release of 1-Methylcyclopropene and modified atmosphere packaging. J Food Sci 2012; 77: 188–193.
Lütken H, Clarke JL, Müller R . Review: Genetic engineering and sustainable production of ornamentals: Current status and future directions. Plant Cell Rep 2012; 31: 1141–1157.
Onozaki T . Improvement of flower vase life using cross-breeding techniques in carnation (Dianthus caryophyllus L.). Jarq-Jpn Agr Res Q 2008; 42: 137–144.
Hvoslef-Eide AK, Fjeld T, Einset JW . Breeding Christmas begonia Begonia × cheimantha Everett for increased keeping quality by traditional and biotechnological methods. Acta Hortic 1995; 405: 197–204.
Onozaki T, Yagi M, Tanase K, Shibata M . Crossings and selections for six generations based on flower vase life to create lines with ethylene resistance or ultra-long vase life in carnations (Dianthus caryophyllus L.). J Jpn Soc Hortic Sci 2011; 80: 486–498.
Wu MJ, Zacarias L, Reid MS . Variation in the senescence of carnation (Dianthus caryophyllus L.) cultivars. II. Comparison of sensitivity to exogenous ethylene and of ethylene binding. Sci Hortic 1991; 48: 109–116.
Onozaki T, Ikeda H, Yamaguchi T . Genetic improvement of vase life of carnation flowers by crossing and selection. Sci Hortic 2001; 87: 107–120.
Onozaki T, Ikeda H, Shibata M . Video evaluation of ethylene sensitivity after anthesis in carnation (Dianthus caryophyllus L.) flowers. Sci Hortic 2004; 99: 187–197.
Tanase K, Onozaki T, Satoh S, Shibataa M, Ichimura K . Differential expression levels of ethylene biosynthetic pathway genes during senescence of long-lived carnation cultivars. Postharvest Biol Technol 2008; 47: 210–217.
Tanase K, Otsu S, Satoh S, Onozaki T . Expression and regulation of senescence-related genes in carnation flowers with low ethylene production during senescence. J Jpn Soc Hortic Sci 2013; 82: 179–187.
Heuser CW, Evensen KB . Cut flower longevity of peony. J Am Soc Hortic 1986; 111: 896–899.
van Doorn WG . Categories of petal senescence and Abscission: A re-evaluation. Ann Bot 2001; 87: 447–456.
Clark EMR, Dole JM, Carlson AS, Moody EP, McCall IF et al. Vase life of new cut flower cultivars. Hort Technol 2010; 20: 1016–1025.
Woltering EJ, van Doorn WG . Role of ethylene in senescence of petals morphological and Taxonomical relationships. J Exp Bot 1988; 39: 1605–1616.
Müller R, Andersen AS, Serek M . Differences in display life of miniature potted roses (Rosa hybrida L.). Sci Hortic 1998; 76: 59–71.
Müller R, Stummann BM, Sisler EC, Serek M . Cultivar differences in regulation of ethylene production of miniature rose flowers (Rosa hybrida L.). Gartenbauwissenshaft 2001; 66: 34–38.
Tan H, Liu X, Ma N, Xue J, Lu W et al. Ethylene-influenced flower opening and expression of genes encoding ETRS, CTRS, and EIN3 in two cut rose cultivars. Postharvest Biol Technol 2006; 40: 97–105.
Xue J, Li Y, Tan H, Yang F, Ma N et al. Expression of ethylene biosynthetic and receptor genes in rose floral tissues during ethylene-enhanced flower opening. J Exp Bot 2008; 59: 2161–2169.
Macnish AJ, Leonard RT, Borda AM, Nell TA . Genotypic variation in the postharvest performance and ethylene sensitivity of cut rose flowers. J Hortic Sci 2010; 45: 790–796.
Clark DG, Dervinis C, Barrett JE, Nell TA . Using a seedling hypocotyl elongation assay as a genetic screen for ethylene sensitivity of seedling geranium cultivars. Hort Technol 2001; 11: 297–302.
Kim HJ, Craig R, Brown KM . Genetic variation in ethylene responsiveness of Regal Pelargonium. J Am Soc Hortic 2006; 131: 122–126.
Howard NP, Stimart D, de Leon N, Havey MJ, Martin W . Diallel analysis of floral longevity in Impatiens walleriana. J Am Soc Hortic 2012; 137: 47–50.
Martin WJ, Stimart DP . Early generation evaluation in Antirrhinum majus for prediction of cut flower postharvest longevity. J Am Soc Hortic 2003; 128: 876–880.
Weber JA, Martin WJ, Stimart DP . Genetics of postharvest longevity and quality traits in late generation crosses of Antirrhinum majus L. J Am Soc Hortic 2005; 130: 694–699.
Martin WJ, Stimart DP . Genetic analysis of advanced populations in Antirrhinum majus L. with special reference to cut flower postharvest longevity. J Am Soc Hortic 2005; 130: 434–441.
Friedman H, Hagiladi A, Resnick N, Barak A, Umiel N . Ethylene-insensitive related phenotypes exist naturally in a genetically variable population of Dianthus barbatus. Theor Appl Genet 2001; 103: 282–287.
Krahl KH, Randle WM . Genetics of floral longevity in Petunia. J Hortic Sci 1999; 34: 339–340.
Sun Y, Christensen B, Liu F, Wang H, Müller R . Effects of ethylene and 1-MCP (1-methylcyclopropene) on bud and flower drop in mini Phalaenopsis cultivars. Plant Growth Regul 2009; 59: 83–91.
Chang YCA, Lin WL, Hou JY, Yen WY, Lee N . Concentration of 1-methylcyclopropene and the duration of its application affect anti-ethylene protection in Phalaenopsis. Sci Hortic 2013; 153: 117–123.
Serek M, Reid MS . Ethylene and postharvest performance of potted Kalanchoë. Postharvest Biol Technol 2000; 18: 43–48.
Macnish AJ, Irving DE, Joyce DC, Vithanage V, Wearing AH et al. Variation in ethylene-induced postharvest flower abscission responses among Chamelaucium Desf. (Myrtaceae) genotypes. Sci Hortic 2004; 102: 415–432.
Bicknell R . Breeding cut flower cultivars of Leptospermum using interspecific hybridisation. New Zeal J Crop Hortic 1995; 23: 412–421.
Beal PR, Joyce A . Cut flower characteristics of terminal flowering tropical Grevillea: A brief review. Aust J Exp Agric 1999; 39: 781–94.
Shibata M . Importance of genetic transformation in ornamental plant breeding. Plant Biotech J 2008; 25: 3–8.
Riek JD, Debener T . Present use of molecular markers in ornamental breeding. In: Proc. 23rd Intl. Eucarpia Symp. (Sec. Ornamentals) on “Colourful Breeding and Genetics” Part II. Eds. : van Tuyl, J. M and de Vries, D. P . Acta Hort 2010; 855: 77–84.
Yagi M . Application of DNA markers for breeding carnations resistant to bacterial wilt. Jpn Agr Res Q 2013; 47: 29–35.
Izumikawa Y, Nakamura I, Mii M . Interspecific hybridization between Kalanchoe blossfeldiana and several wild Kalanchoe species with ornamental value. Acta Hortic 2009; 743: 59–66.
Sasaki K, Aida R, Niki T, Yamaguchi H, Narumi T et al. High-efficiency improvement of transgenic torenia flowers by ion beam irradiation. Plant Biotech J 2008; 25: 81–89.
Bologna P, Soto S, Prina AR, Borja M . X-rays as a tool for inducing variants of Calibrachoa. Acta Hortic 2012; 937: 941–946.
McCallum CM, Comai L, Greene EA, Henikoff S . Targeting Induced Local Lesions In Genomes (TILLING) for plant functional genomics. Plant Physiol 2000; 123: 439–442.
Dahmani-Mardas F, Troadec C, Boualem A, Lévêque S, Alsadon AA et al. Engineering melon plants with improved fruit shelf life using the TILLING Approach. PLoS One 2010; 5: e15776.
Jiang P, Chen Y, Wilde HD . Optimization of EMS Mutagenesis on petunia for Tilling. Adv Crop Sci Techol 2014; 2:141.
Xiong JS, Ding J, Li Y . Genome-editing technologies and their potential application in horticultural crop breeding. Hort Res 2015; 2: 15019.
Savin KW, Baudinette SC, Graham MW, Michael MZ, Nugent GD et al. Antisense ACC Oxidase RNA delays carnation petal senescence. J Hortic Sci 1995; 30: 970–972.
Kiss E, Veres A, Galli Z . Production of transgenic carnation with anti-sense ACS (1-aminocyclopropane-1-carboxylate synthase) gene. Int J Hortic Sci 2000; 6: 103–107.
Iwazaki Y, Kosugi Y, Waki K, Yoshioka T, Satoh S . Generation and ethylene production of transgenic car nations harboring ACC synthase cDNA in sense or antisense orientation. J Appl Hortic 2004; 6: 67–71.
Aida R, Yoshida T, Ichimura K, Goto R, Shibata M . Extension of flower longevity in transgenic torenia plants incorporating ACC oxidase transgene. Plant Sci 1998; 138: 91–101.
Chen JC, Jiang CZ, Gookin TE, Hunter DA, Clark DG et al. Chalcone synthase as a reporter in virus-induced gene silencing studies of flower senescence. Plant Mol Biol 2004; 55: 521–530.
Einset JW, Kopperud C . Antisense ethylene genes for begonia flowers. Acta Hortic 1995; 405: 190–196.
Klee HJ, Hayford MB, Kretzmer KA, Barry GF, Kishore GM . Control of ethylene synthesis by expression of a bacterial enzyme in transgenic tomato plants. Plant Cell 1991; 3: 1187–1193.
Wilkinson JQ, Lanahan MB, Clark DG, Bleecker AB, Chang C et al. A dominant mutant receptor from Arabidopsis confers ethylene insensitivity in heterologous plants. Nat Biotechnol 1997; 15: 444–447.
Sanikhani M, Mibus H, Stummann BM, Serek M . Kalanchoe blossfeldiana plants expressing the Arabidopsis etr1-1 allele show reduced ethylene sensitivity. Plant Cell Rep 2008; 27: 729–737.
Sriskandarajah S, Mibus H, Serek M . Transgenic Campanula carpatica plants with reduced ethylene sensitivity. Plant Cell Rep 2007; 26: 805–813
Sriskandarajah S, Mibus H, Serek M . Introduction of ethylene insensitivity in campanula carpatica flowers by Genetic Manipulation with Etr1-1. In: Proc. 6th International Postharvest Symposium. (eds.): Erkan, M. and Aksoy, U . Acta Hort 2010; 877: 1111–1114.
Bovy AG, Angenent GC, Dons HJM, van Altvorst AN . Heterologous expression of the Arabidopsis etr1-1 allele inhibits the senescence of carnation flowers. Mol Breeding 1999; 5: 301–308.
Gubrium EK, Clevenger DJ, Clark DG, Barrett JE, Nell TA . Reproduction and horticultural performance of transgenic ethylene-insensitive petunias. J Am Soc Hortic 2000; 125: 277–281.
Cui ML, Takada K, Ma B, Ezura H . Overexpression of a mutated melon ethylene receptor gene Cm-ETR1/H69A confers reduced ethylene sensitivity in a heterologous plant, Nemesia strumosa. Plant Science 2004; 167: 253–258.
Czarny JC, Grichko VP, Glick BR . Genetic modulation of ethylene biosynthesis and signaling in plants. Biotechnol Adv 2006; 24: 410–419.
Gan S, Amasino RM . Inhibition of leaf senescence by autoregulated production of cytokinin. Science New Series 1995; 270: 1986–1988.
Du L, Lou Q, Zhang X, Jiao S, Liu Y et al. Construction of flower-specific chimeric promoters and analysis of their activities in transgenic torenia. Plant Mol Biol Rep 2014; 32: 234–245.
Wang H, Stier G, Lin J, Liu G, Zhang Z et al. Transcriptome changes associated with delayed flower senescence on transgenic petunia by inducing expression of etr1-1, a Mutant ethylene receptor. PLoS One 2013; 8: e65800.
Caddick MX, Greenland AJ, Jepson I, Krause KP, Qu N et al. An ethanol inducible gene switch for plants used to manipulate carbon metabolism. Nat Biotechnol 1998; 16: 177–180.
Garoosi GA, Salter MG, Caddick MX, Tomsett AB . Characterization of the ethanol-inducible alc gene expression system in tomato. J Exp Bot 2005; 56: 1635–1642.
Moore I, Samalova M, Kurup S . Transactivated and chemically inducible gene expression in plants. Plant J 2006; 45: 651–683.
Cobb D, Schneiter N, Guo S, Humiston GA, Harriman B et al. Flower specific expression of an ethylene receptor (ETR1-1) confers ethylene insensitivity in transgenic Petunia. In: XXVIth International Horticultural Congress Book of Abstracts, Toronto, 2002, 83.
Shaw JF, Chen HH, Tsai MF, Kuo CI, Huang LI . Extended flower longevity of petunia hybrida plants transformed with boers, a mutated ERS gene of Brassica oleracea. Mol Breeding 2002; 9: 211–216.
Nukui H, Kudo S, Yamashita A, Satoh S . Repressed ethylene production in the gynoecium of long-lasting flowers of the carnation ‘White Candle’: Role of the gynoecium in carnation flower senescence. J Exp Bot 2004; 55: 641–650.
Raffeiner B, Serek M, Winkelmann T . Agrobacterium tumefaciens-mediated transformation of Oncidium and Odontoglossum orchid species with the ethylene receptor mutant gene etr1-1. Plant Cell Tiss Org 2009; 98: 125–134.
Ciardi J, Barry K, Shibuya K, Nourizadeh S, Ecker J et al. Increased flower longevity in petunia through manipulation of ethylene signaling genes. In: Proceedings of the NATO Advanced Research Workshop on Biology and Biotechnology of the Plant Hormone Ethylene III., Eds. Vendrell, M., Klee, H., Pech, J. C. and Romojaro, F., 2003; 370–372.
Shibuya K, Berry KG, Ciardi JA, Loucas HM, Underwood BA et al. The central role of PhEIN2 in ethylene responses throughout plant development in petunia. Plant Physiol 2004; 136: 2900–2912.
Chang X, Donnelly L, Sun D, Rao J, Reid MS et al. A petunia homeodomain-leucine zipper protein, PhHD-Zip, Plays an important role in flower senescence. PLoS One 2014; 9: e88320.
Lusser M, Parisi C, Plan D, Rodríguez-Cerezo E . Deployment of new biotechnologies in plant breeding. Nat Biotechnol 2012; 30: 231–239.
Podevin N, Devos Y, Davies HV, Nielsen KM . Transgenic or not? No simple answer! New biotechnology‐based plant breeding techniques and the regulatory landscape. EMBO reports 2012; 13: 1057–1061.
Carroll D . Genome engineering with zinc-finger nucleases. J Genetics 2011; 188: 773–782.
Townsend JA, Wright DA, Winfrey RJ, Fu F, Maeder ML et al. High-frequency modification of plant genes using engineered zinc-finger nucleases. Nature 2009; 459: 442–445.
Lor VS, Starker CG, Voytas DF, Weiss D, Olszewski NE . Targeted mutagenesis of the tomato PROCERA gene using transcription activator-like effector nucleases. Plant Physiol 2014; 166: 1288.
Bortesi L, Fischer R . The CRISPR/Cas9 system for plant genome editing and beyond. Biotechnol Adv 2015; 33: 41–52.
Mor Y, Spiegelstein H, Halevy AH . Inhibition of ethylene biosynthesis in carnation petals by cytokinin. Plant Physiol 1983; 71: 541–546.
Hoeberichts FA, van Doorn WG, Vorst O, Hall RD, van Wordragen MF . Sucrose prevents up-regulation of senescence-associated genes in carnation petals. J Exp Bot 2007; 58: 2873–2885.
van Doorn WG, Woltering EJ . Physiology and molecular biology of petal senescence. J Exp Bot 2008; 59: 453–480.
Taverner EA, Letham DS, Wang J, Cornish E . Inhibition of carnation petal in-rolling by growth retardants and cytokinins. AustJ Plant Physiol 2000; 27: 357–362.
Chang H, Jones ML, Banowets GM, Clarke DG . Overproduction of cytokinins in petunia flowers transformed with PSAG12-IPT delays corolla senescence and decreases sensitivity to ethylene. Plant Physiol 2003; 132: 539–544.
Zakizadeh H, Lütken H, Sriskandarajah S, Serek M, Müller R . Transformation of miniature potted rose (Rosa hybrida cv. Linda) with PSAG12-ipt gene delays leaf senescence and enhances resistance to exogenous ethylene. Plant Cell Rep 2013; 32: 195–205.
Trivellini A, Ferrante A, Vernieri P, Serra G . Effects of abscisic acid on ethylene biosynthesis and perception in Hibiscus rosa-sinensis L. flower development. J Exp Bot 2011; 62: 5437–5452.
Nomura Y, Harada T, Morita S, Kubota S, Koshioka M et al. Role of ABA in triggering ethylene production in the gynoecium of senescing carnation flowers: Changes in ABA content and expression of genes for ABA biosynthesis and action. Jpn Soc Hortic Sci 2013; 82: 242–254.
Liao WB, Zhang ML, Yu JH . Role of nitric oxide in delaying senescence of cut rose flowers and its interaction with ethylene. Sci Hortic 2013; 155: 30–38.
Zhang C, Wang Y, Fu J, Dong L, Gao S et al. Transcriptomic analysis of cut tree peony with glucose supply using the RNA-Seq technique. Plant Cell Rep 2014; 33: 111–129.
Müller R, Owen CA, Xu ZT, Welander M, Stummann BM . Genetic control of ethylene perception and signal transduction related to flower senescence. J Food Agric Environ 2003; 1: 87–94.
van Doorn WG . Is petal senescence due to sugar starvation? Plant Physiol 2004; 134: 35–42.
Shimizu H, Ichimura K . Effects of silver thiosulfate complex STS, sucrose and their combination on the quality and vase life of cut Eustoma flowers. J Jpn Soc Hortic Sci 2005; 74: 381–385.
Zhang C, Liu M, Fu J, Wang Y, Dong L . Exogenous sugars involvement in senescence and ethylene production of tree peony ‘Luoyang Hong’ cut flowers. Korean J Hortic Sci & Technol 2012; 30: 718–724.
Chen MK, Hsu WH, Lee PF, Thiruvengadam M, Chen HI et al. The MADS box gene, FOREVER YOUNG FLOWER, acts as a repressor controlling floral organ senescence and abscission in Arabidopsis. Plant J 2011; 68: 168–185.
Fernandez DE, Heck GR, Perry SE, Patterson SE, Bleecker AB et al. The embryo MADS domain factor AGL15 Acts post embryonically: Inhibition of perianth senescence and abscission via constitutive expression. Plant Cell 2000; 12: 183–197.
Fang SC, Fernandez DE . Effect of regulated overexpression of the MADS domain factor AGL15 on flower senescence and fruit maturation. Plant Physiol 2002; 130: 78–89.
Zheng Q, Zheng Y, Perry SE . AGAMOUS-Like15 promotes somatic embryogenesis in arabidopsis and soybean in part by the control of ethylene biosynthesis and response. Plant Physiol 2013; 161: 2113–2127.
Fernandez DE, Wang CT, Zheng Y, Adamczyk BJ, Singhal R et al. The MADS-domain factors AGAMOUS-LIKE15 and AGAMOUS-LIKE18, along with SHORT VEGETATIVE PHASE and AGAMOUS-LIKE24, are necessary to block floral gene expression during the vegetative phase. Plant Physiol 2014; 165: 1591–1603.
Tsai WC, Lee PF, Chen HI, Hsiao YY, Wei WJ et al. PeMADS6, a GLOBOSA/PISTILLATA-like Gene in Phalaenopsis equestris Involved in petaloid formation, and correlated with flower longevity and ovary development. Plant Cell Physiol 2005; 46: 1125–1139.
Kandasamy MK, Deal RB, McKinney EC, Meagher RB . Silencing the nuclear actin-related protein AtARP4 in Arabidopsis has multiple effects on plant development, including early flowering and delayed floral senescence. Plant J 2005; 41: 845–858.
Xu X, Jiang CZ, Donnelly L, Reid MS . Functional analysis of a RING domain ankyrin repeat protein that is highly expressed during flower senescence. J Exp Bot 2007; 58: 3623–3630.
Jones RB, Serek M, Kuo CL, Reid MS . The effect of protein synthesis inhibition on petal senescence in cut bulb flowers. J Am Soc Hortic Sci 1994; 119: 1243–1247.
Stier GN, Kumar P, Jiang CZ, Reid MS . Silencing of a proteasome component delays floral senescence. Hortic Sci 2010; 45: S147.
Christensen B, Müller R . Improved postharvest life and ethylene tolerance in Kalanchoe blossfeldiana Transformed with rol-Genes of Agrobacterium rhizogenes. Proc. IXth Intl. Symp. on Postharvest Quality of Ornamental Plants Ed.: Ottosen, C.-O. . Acta Hort, 2009; 847: 87–93.
Lütken H, Jensen EB, Christensen B . Development and evaluation of a non-GMO breeding technique exemplified by Kalanchoë. In: Proc. 7th, IS on In Vitro Culture and Horticultural Breeding, Ed.: D. Geelen . Acta Hort 2012; 961: 51–58.
Lütken H, Wallström SV, Jensen EB, R. Inheritance of rol-genes from Agrobacterium rhizogenes through two generations in Kalanchoë. Euphytica 2012; 188: 397–407.
da Silva JAT, Chin DP, Van PT, Mii M . Transgenic orchids. Sci Hortic 2011; 130: 673–680.
Brand MH . Ornamental plant transformation. J Crop Imp 2006; 17: 27–50.
Chandler SF, Sanchez C . Genetic modification; the development of transgenic ornamental plant varieties. Plant Biotech J 2012; 10: 891–903.
Lusser M, Davies HV . Comparative regulatory approaches for groups of new plant breeding techniques. N Biotechnol 2013; 30: 437–446.
Dirks R, van Dun K, de Snoo CB, van den Berg M, Lelivelt CL et al. Reverse breeding: A novel breeding approach based on engineered meiosis. Plant Biotech J 2009; 7: 837–845.
Seeds of Change. Nature 2015; 520: 131–132.
Cibus. Press Release, BASF and Cibus announce collaboration for herbicide tolerant crops. 2015. Available at http://www.cibus.com/press_release.php?date=071007 (accessed 20 April 2015).
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Competing interests
The authors have no conflicts to declare.
Rights and permissions
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 Unported License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/4.0/
About this article
Cite this article
Olsen, A., Lütken, H., Hegelund, J. et al. Ethylene resistance in flowering ornamental plants – improvements and future perspectives. Hortic Res 2, 15038 (2015). https://doi.org/10.1038/hortres.2015.38
Received:
Revised:
Accepted:
Published:
DOI: https://doi.org/10.1038/hortres.2015.38
This article is cited by
-
Integrated analysis of transcriptomic and proteomic data from tree peony (P. ostii) seeds reveals key developmental stages and candidate genes related to oil biosynthesis and fatty acid metabolism
Horticulture Research (2019)
-
Transcriptome profiling reveals regulatory mechanisms underlying corolla senescence in petunia
Horticulture Research (2018)
-
Improved leaf and flower longevity by expressing the etr1-1 allele in Pelargonium zonale under control of FBP1 and SAG12 promoters
Plant Growth Regulation (2018)
-
A natural frameshift mutation in Campanula EIL2 correlates with ethylene insensitivity in flowers
BMC Plant Biology (2016)
