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Gene editing

This collection describes the principles of the latest genome-editing technologies and discusses the advantages and challenges of genome-editing technologies in horticultural crop breeding.

Editors' picks

A group led by Dr. Yi Li of University of Connecticut, USA has developed a technique to reliably create desirable mutations in crop plants without introducing any foreign DNA, thus generating non-transgenic mutant plants. Their technique will be particularly important for application of genome editing technologies in perennial crop plants. Genome editing technologies have been used to introduce desired mutations into plants but the approach normally incorporates foreign genes such as Cas9 into the plant’s genome. To avoid this, Dr. Li’s team has used Agrobacterium to transiently express the CRISPR/Cas9 components, a bacterium commonly used to genetically engineer plants. With their method, CRISPR/Cas9 from the bacteria edit the plant genome without introducing any foreign DNA, and then a two-step screening process is used to identify non-transgenic mutant plants. This new method provides a reliable and efficient alternative for producing non-transgenic genetically engineered crops.

Article | Open Access | | Horticulture Research

Chinese researchers have identified a new gene which regulates the ripening of tomatoes. Several genes known to control tomato ripening are members of the NAC family of regulators. To identify others, a team led by Daqi Fu of China Agricultural University blocked the expression of candidate NAC genes. The discovered that silencing NOR-like1 repressed ripening, leaving the tomatoes partially green. The team also engineered plants with defective copies of NOR-like1 and found that this delayed ripening and eventually resulted in partially ripe fruit and impaired seed development. RNA sequencing of these lines revealed that NOR-like1 directly regulates genes involved in ethylene synthesis, carotenoid accumluation, chlorophyll metabolism, and cell wall breakdown. These findings clearly demonstrate a key role for NOR-like1 as a positive regulator of tomato ripening and a potential tool for controlling this important process.

Article | Open Access | | Horticulture Research

A new generation of genetic techniques could revolutionise crop breeding, but also poses technical and legal challenges. Traditional crop breeding is a slow and relatively unpredictable process. Genetic modification overcomes these problems but, especially in Europe, raises consumer concerns surrounding cross-contamination and unintended genetic effects. An Italian team led by Lorenza Dalla Costa at the Fondazione Edmund Mach, San Michele all'Adige, reviews two cutting-edge techniques that may avoid these issues. ‘Cisgenesis’ is the transfer of genes between very closely related plants, mimicking the process of traditional crop breeding. ‘Genome editing’ uses targeted enzymes to switch off specific genes, such as those conferring susceptibility to pathogens. In high-value perennial crops such as grapevine, these techniques could prove invaluable; however, education, improved legislation, and further technical development are all required before they can be used in practice.

Review Article | Open Access | | Horticulture Research

Researchers in China have shown that the gene-editing system CRISPR/Cas9 can be used to efficiently mutate genes of interest in cabbage. Cabbage plants normally do not self-pollinate, making the use of traditional mutagens difficult. Hongyuan Song of Southwest University therefore turned to CRISPR/Cas9, a system which can introduce precise mutations into specific genes. Song’s team targeted three genes: one related to coloration, another to self-incompatibility, and a third involved in pollen development. They began by mutating each gene separately to test the system’s efficiency. Next, they built a CRISPR/Cas9 construct that would simultaneously mutate the pollen gene and the self-incompatibility gene. One-third of the plants produced using the construct had mutations in both of the target genes. These findings demonstrate that CRISPR/Cas9 is a valuable tool for trait improvement and genetic research in cabbage.

Article | Open Access | | Horticulture Research

The regulatory circuits that govern the expression of genes required for ripening in tomato plants are highly redundant. Fleshy fruits that use the hormone ethylene to regulate ripening have developed independently multiple times in the history of the angiosperms. Guiqin Qu at China Agricultural University in Beijing and colleagues working on the fruitENCODE project are exploring the genetic and epigenetic basis of this convergent evolution. In tomatoes, three transcription factors have been shown to control ethylene production and regulate ripening. However, when gene editing techniques were used to introduce mutations that interfere with the function of these transcription factors, partial ripening or a delay in ripening was observed. The fact that ripening was not abolished indicates that the ripening process is more robust and complex than previously thought.

Article | Open Access | | Horticulture Research