Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Plant genetic engineering for biofuel production: towards affordable cellulosic ethanol

A Retraction to this article was published on 02 March 2010

Key Points

  • Recently, biofuels have received increasing global attention because of finite reserves of fossil fuels, which particularly affects industrialized nations, and an increased knowledge of the effect of the extraction and use of fossil fuels on the environment. These factors have led to most nations initiating research into the production and use of biofuels as the main source of transportation fuel.

  • At present, the main sources of biofuel ethanol include starch from corn seeds and sugar from sugarcane. However, neither starch nor sugar can be produced at a sufficient level to meet biofuel needs. In addition, increasing the use of these products for biofuel production would push up food prices. Therefore, using cellulosic material for biofuel production is an important area of research.

  • One environmental advantage of biofuel crop production is a reduction of greenhouse gas levels owing to increased photosynthesis. In addition, conversion of biomass to ethanol and the burning of the ethanol fuel reduces greenhouse gas emissions compared with petroleum fuel, so that its use does not contribute to an increase in net carbon dioxide.

  • Important steps that are associated with commercial production of cellulosic ethanol include production, transportation and storage of cellulosic biomass; pretreatment processes to break down the biomass into intermediates and remove its lignin; production of cellulases in microbial bioreactors used to convert biomass into fermentable sugars; and fermentation of sugars into ethanol.

  • Problems presently associated with the commercial production of cellulosic ethanol include the high costs of production of cellulases in microbial bioreactors and the costs of pretreatment processes of lignocellulosic matter, which together bring the price of cellulosic ethanol to about two to three-fold higher than the price of corn grain ethanol.

  • In nature, plant cell walls are deconstructed (decomposed) by hydrolysis enzymes (including cellulases and hemicellulases), which are produced mainly by microorganisms.

  • One important area of research is the genetic modification of relevant feedstock crops to self-produce heterologous cellulases. To date a few non-biofuel model crops (such as Arabidopsis thaliana, tobacco and alfalfa) and feedstock biofuel crops (such as corn and rice) have been developed as biofactories that self-produce microbial cellulases within their biomass.

  • Subcellular targeting is important for the safe accumulation of these heterologous molecules. Microbial cellulases that are produced in the cytoplasm of biomass biofuel crops have been targeted for safe accumulation in subcellular compartments such as the apoplast, chloroplast, mitochondria, endoplasmic reticulum and vacuole — away from cytoplasmic metabolic activities. New crop genotypes that have modified lignin levels and configurations can also reduce pretreatment processes, and have been developed for species including poplar, alfalfa, tobacco and corn.

  • Plant cell walls contain cellulose, hemicellulose, pectin and lignin. A complete understanding of the biosynthetic pathways involved is lacking, and is an important area of ongoing research, with the aim of manipulating these pathways to optimize plant cell-wall composition for cellulosic bioethanol production.

  • Cellulosic biomass can be increased by the transfer of genes that shift energy from the reproductive to the vegetative state, and possibly through overexpressing enzymes that are associated with the biosynthesis of plant cellulose and hemicellulose.

Abstract

Biofuels provide a potential route to avoiding the global political instability and environmental issues that arise from reliance on petroleum. Currently, most biofuel is in the form of ethanol generated from starch or sugar, but this can meet only a limited fraction of global fuel requirements. Conversion of cellulosic biomass, which is both abundant and renewable, is a promising alternative. However, the cellulases and pretreatment processes involved are very expensive. Genetically engineering plants to produce cellulases and hemicellulases, and to reduce the need for pretreatment processes through lignin modification, are promising paths to solving this problem, together with other strategies, such as increasing plant polysaccharide content and overall biomass.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Plant plasma membrane and cell-wall structure.
Figure 2: Overview of cellulosic ethanol production.
Figure 3: Lignin biosynthesis.

References

  1. Bordetsky, A., Hwang, R., Korin, A., Lovaas, D. & Tonachel, L. Securing America: Solving Our Oil Dependence Through Innovation (Natural Resources Defense Council, New York, 2005)

    Google Scholar 

  2. Schlamadinger, B. et al. Towards a standard methodology for greenhouse gas balances of bioenergy systems in comparison with fossil energy systems. Biomass Bioenergy 13, 359–375 (1997).

    CAS  Article  Google Scholar 

  3. National Corn Growers Association. World of corn [online], (2007).

  4. Department of Energy. DOE selects six cellulosic ethanol plants for up to $385 million in federal funding [online], (2007). Shows the United States' recognition of the need to allocate funds for the design and establishment of the first six commercial cellulosic ethanol plants.

  5. Knauf, M. & Moniruzzaman, M. Lignocellulosic biomass processing: a perspective. Int. Sugar J. 106, 147–150 (2004).

    CAS  Google Scholar 

  6. Sticklen, M. B. in Proc. 2nd Int. Ukrainian Conf. Biomass for Energy 133–136 (Ukraine Natl Acad. Sci., Kiev, 2004).

    Google Scholar 

  7. Carpita, N. & McCann, M. in Biochemistry & Molecular Biology of Plants Ch. 2 (eds Buchanan, B., Gruissem, W. & Jones, R. L.) (John Wiley & Sons, New Jersey, 2002).

    Google Scholar 

  8. Ding, S. Y. & Himmel, M. E. The maize primary cell wall microfibril: a new model derived from direct visualization. J. Agric. Food Chem. 54, 597–606 (2006).

    CAS  Article  PubMed  Google Scholar 

  9. Bothast, R. J. & Schlicher, M. A. Biotechnological processes for conversion of corn into ethanol. Appl. Microbiol. Biotechnol. 67, 19–25 (2005).

    CAS  Article  PubMed  Google Scholar 

  10. Mosier, N. et al. Features of promising technologies for pretreatment of lignocellulosic biomass. Biores. Tech. 96, 673–686 (2005).

    CAS  Article  Google Scholar 

  11. Somerville, C. S., The billion-ton biofuels vision. Science 312, 1277 (2006). Describes the availability of lands and the needs for production of a billion ton biomass in the United States to decrease its dependency on foreign oil.

    CAS  Article  PubMed  Google Scholar 

  12. Somleva, M. N., Tomaszewski, Z. & Cong, B. V. Agrobaterium-mediated genetic transformation of switchgrass. Crop Sci. 42, 2080–2087 (2002).

    CAS  Article  Google Scholar 

  13. Sticklen, M. & Oraby, H. Shoot apical meristem: a sustainable explant for genetic engineering of cereal crops. In Vitro Cell. Dev. Plant 41, 187–200 (2005).

    CAS  Article  Google Scholar 

  14. Sticklen, M. B. Plant genetic engineering to improve biomass characteristics for biofuels. Curr. Opin. Biotechnol. 17, 315–319 (2006).

    CAS  Article  PubMed  Google Scholar 

  15. Fischer, R., Stoger, E., Schillberg, S., Christou, P. & Twyman, R. Plant-based production of biopharmaceuticals. Curr. Opin. Plant Biol. 7, 152–158 (2004).

    CAS  Article  PubMed  Google Scholar 

  16. Howard, J. A., & Hood, E. Bioindustrial and biopharmaceutical products produced in plants. Adv. Agron. 85, 91–124 (2005).

    CAS  Article  Google Scholar 

  17. Horn, M. E., Woodard, S. L. & Howard, J. A. Plant molecular farming: systems and products. Plant Cell Rep. 22, 711–720 (2004).

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  18. Teymouri, F., Alizadeh, H., Laureano-Perez, L., Dale, B. E. & Sticklen, M. B. Effects of ammonia fiber explosion treatment on activity of endoglucanase from Acidothermus cellulolyticus in transgenic plant. Appl. Biochem. Biotechnol. 116, 1183–1192 (2004).

    Article  Google Scholar 

  19. Ransom, C. B. et al. Heterologous Acidothermus cellulolyticus 1,4-β-endoglucanase E1 produced within the corn biomass converts corn stover into glucose. Appl. Biochem. Biotechnol. 36, 207–220 (2007).

    Google Scholar 

  20. Oraby, H. et al. Enhanced conversion of plant biomass into glucose using transgenic rice-produced endoglucanase for cellulosic ethanol. Transgenic Res. 16, 739–749 (2007). An excellent example of producing a cell-wall hydrolysis enzyme in rice, a globally important crop.

    CAS  Article  PubMed  Google Scholar 

  21. National Research Council. Bioconfinement of Genetically Engineered Organisms (Natl Acad. Sci., Washington D. C., 2004). A comprehensive review of the designs and methods that could be used before production of genetically engineered organisms in order to reduce risks and public concerns.

  22. Okumura, S. et al. Transformation of poplar (Poplus alba) plastids and expression of foreign proteins in tree chloroplasts. Transgenic Res. 15, 637–646 (2006).

    CAS  Article  PubMed  Google Scholar 

  23. Schillberg, S., Zimmermann, S., Voss, A. & Fischer, R. . Apoplastic and cytosolic expression of full-size antibodies and antibody fragments in Nicotiana tabacum. Transgenic Res. 8, 255–263 (1999).

    CAS  Article  PubMed  Google Scholar 

  24. Schillberg, S. Fischer, R. & Emans, N. Molecular farming of recombinant antibodies in plants. Cell. Mol. Life Sci. 60, 433–445 (2003).

    CAS  Article  PubMed  Google Scholar 

  25. Ziegler, M. T., Thomas, S. R. & Danna, K. J. Accumulation of a thermostable endo-1,4-D-glucanase in the apoplast of Arabidopsis thaliana leaves. Mol. Breeding 6, 37–46 (2000).

    CAS  Article  Google Scholar 

  26. Hyunjong, B., Lee, D. S. & Hwang, I. Dual targeting of xylanase to chloroplasts and peroxisomes as a means to increase protein accumulation in plant cells. J. Exp. Bot. 57, 161–169 (2006).

    CAS  Article  PubMed  Google Scholar 

  27. Dai, Z., Hooker, B. S., Anderson, D. B. & Thomas, S. R. Improved plant-based production of E1 endoglucanase using potato: expression optimization and tissue targeting. Mol. Breeding 6, 277–285 (2000).

    CAS  Article  Google Scholar 

  28. Kawagoe, Y. & Delmer, D. P. Pathways and genes involved in cellulose biosynthesis. Genet. Eng. 19, 63–87 (1997).

    CAS  Article  Google Scholar 

  29. Arioli, T. et al. Molecular analysis of cellulose biosynthesis in Arabidopsis. Science 279, 717–720 (1998).

    CAS  Article  PubMed  Google Scholar 

  30. Bolwell, G. P. Biosynthesis of plant cell wall polysaccharides. Trends Glycosci. Glycotechnol. 12, 143–160 (2000).

    CAS  Article  Google Scholar 

  31. Persson, S., Wei, H., Milne, J., Page, G. P. & Somerville, C. R. Identification of genes required for cellulose synthesis by regression analysis of public microarray data sets. Proc. Natl Acad. Sci. USA 102, 8633–8638 (2005).

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  32. Andersson-Gunneras, S. et al. Biosynthesis of cellulose-enriched tension wood in Populus: global analysis of transcripts and metabolites identifies biochemical and developmental regulators in secondary wall biosynthesis. Plant J. 45, 144–165 (2006).

    Article  CAS  PubMed  Google Scholar 

  33. Haigler, C. H. in The Science and Lore of the Plant Cell Wall: Biosynthesis, Structure and Function (ed. Hayashi, T.) (Brown Walker, Boca Raton, 2006).

    Google Scholar 

  34. Eriksson, M. E., Israelsson, M., Olsson, O. & Moritiz, T. Increased gibberellin biosynthesis in transgenic trees promotes growth, biomass production and xylem fiber length. Nature Biotechnol. 18, 784–788 (2000).

    CAS  Article  Google Scholar 

  35. Sticklen, M. B. Feedstock crop genetic engineering for alcohol fuels. Crop Sci. 47, 2238–2248 (2007).

    CAS  Article  Google Scholar 

  36. Luo, Y., Chen, J. L., Reynolds, J. F., Field, C. B. & Mooney, H. A. Disproportional increases in photosynthesis and plant biomass in a Californian grassland exposed to elevated CO2: a simulation analysis. Funct. Ecol. 11, 696–704 (1997).

    Article  Google Scholar 

  37. Dodd, A. N. et al. Plant circadian clocks increase photosynthesis, growth, survival, and competitive advantage. Science 309, 630–633 (2005).

    CAS  Article  PubMed  Google Scholar 

  38. Smidansky, E. D., Martin, J. M., Hannah, C. L., Fischer, A. M. & Giroux, M. J. Seed yield and plant biomass increases in rice are conferred by deregulation of endosperm ADP-glucose pyrophosphorylase. Planta 216, 656–664 (2003).

    CAS  PubMed  Google Scholar 

  39. Ragauskas, A. J. et al. The path forward for biofuels and biomaterials. Science 311, 484–489 (2006).

    CAS  Article  PubMed  Google Scholar 

  40. Boudet, A.-M. Lignins and lignification: selected issues. Plant Physiol. Biochem. 38, 81–96 (2000).

    CAS  Article  Google Scholar 

  41. Dean, J. F. D. in Biotechnology of Biopolymers: From Synthesis to Patents 4–21 (eds Steinbuchel, A. & Doi, Y.) (John Wiley & Sons, New Jersey, 2004).

    Google Scholar 

  42. Ralph, J. et al. Effects of coumarate 3-hydroxylase down-regulation on lignin structure. J. Biol. Chem. 281, 8843–8853 (2006).

    CAS  Article  PubMed  Google Scholar 

  43. Reddy, M. S. S. et al. Targeted down-regulation of cytochrome P450 enzymes for forage quality improvement in alfalfa (Medicago sativa L). Proc. Natl Acad. Sci. USA 102, 16573–16578 (2005).

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  44. Baucher, M. et al. Down-regulation of cinnamyl alcohol dehydrogenase in transgenic alfalfa (Medicago sativa L) and the effect on lignin composition and digestibility. Plant Mol. Biol. 39, 437–447 (1999).

    CAS  Article  PubMed  Google Scholar 

  45. Pilate, G. et al. Field and pulping performances of transgenic trees with altered lignification. Nature Biotechnol. 20, 607–612 (2002).

    CAS  Article  Google Scholar 

  46. Blaschke, L., Legrand, M., Mai, C. & Polle, A. Lignification and structural biomass production in tobacco with suppressed caffeic/5-hydroxy ferulic acid-O-methyl transferase activity under ambient and elevated CO2 concentrations. Physiol. Plant. 121, 75–83 (2004).

    CAS  Article  PubMed  Google Scholar 

  47. Hu, W. J. et al. Repression of lignin biosynthesis promotes cellulose accumulation and growth in transgenic trees. Nature Biotechnol. 17, 808–812 (1999).

    CAS  Article  Google Scholar 

  48. Li, Y. et al. Processivity, substrate binding, and mechanism of cellulose hydrolysis by Thermobifida fusca Cel9A. Appl. Environ. Microbiol. 73, 3165–3172 (2007).

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  49. Chabannes, M. et al. Strong decrease in lignin content without significant alteration of plant development is induced by simultaneous down-regulation of cinnamoyl CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD) in tobacco plants. Plant J. 28, 257–270 (2001).

    CAS  Article  PubMed  Google Scholar 

  50. Chen, F. & Dixon, R. A. Lignin modification improves fermentable sugar yields for biofuel production. Nature Biotechnol. 25, 759–761 (2007). An excellent example of how plant lignin downregulation can reduce the needs for expensive pretreatment processes.

    CAS  Article  Google Scholar 

  51. Chapple, C., Ladish, M. & Meilan, R. Loosening lignin's grip on biofuel production. Nature Biotechnol. 25, 746–748 (2007).

    CAS  Article  Google Scholar 

  52. Obembe, O. et al. Promiscuous, non-catalytic, tandem carbohydrate-binding modules modulate cell wall structure and development of transgenic tobacco plants. J. Plant Res. 120, 605–617 (2007).

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  53. Boraston, A. B. et al. Carbohydrate-binding modules: fine-tuning polysaccharide recognition. Biochem. J. 382, 769–781 (2004).

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  54. McCartney, L. et al. Differential recognition of plant cell walls by microbial xylan specific carbohydrate-binding modules. Proc. Natl Acad. Sci. USA 103, 4765–4770 (2006).

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  55. Cosgrove, D. J. Loosening of plant cell walls by expansins. Nature 407, 321–326 (2000).

    CAS  Article  PubMed  Google Scholar 

  56. Vaaje-Kolstad, G. et al. Crystal structure and binding properties of the Serratia marcescens chitin-binding protein CBP21. J. Biol. Chem. 280, 11313–11319 (2005).

    CAS  Article  PubMed  Google Scholar 

  57. Yennawar, N. H. et al. Crystal structure and activities of EXPB1 (Zea m 1), a beta expansin and group-1 pollen allergen from maize. Proc. Natl Acad. Sci. USA 103, 14664–14671 (2006).

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  58. Cosgrove, D. J. & Tanada, T. Use of gr2 proteins to modify cellulosic materials and to enhance enzymatic and chemical modification of cellulose. US Patent 20070166805 (2007).

  59. Han, Y. & Chen, H. Synergism between corn stover protein and cellulase. Enz. Microb. Technol. 41, 638–645 (2007).

    CAS  Article  Google Scholar 

  60. Saloheimo, M. et al. Swollenin, a Trichoderma reesei protein with sequence similarity to the plant expansins, exhibits disruption activity on cellulosic materials. Eur. J. Biochem. 269, 4202–4211 (2002).

    CAS  Article  PubMed  Google Scholar 

  61. Han, Y. W. Microbial levan. Adv. Appl. Microbiol. 35, 171–194 (1990).

    CAS  Article  PubMed  Google Scholar 

  62. Graves, M. V. et al. Hyaluronan synthesis in virus PBCV-1 infected Chlorella-like green algae, (1999). Virology 257, 15–23.

    CAS  Article  PubMed  Google Scholar 

  63. Kawasaki, T., Tanaka, M., Fujie, M., Usami, S. & Yamada, T. Chitin synthesis in chlorovirus CVK2-infected Chlorella cells, Virology 302, 123–131 (2003).

    Article  CAS  Google Scholar 

  64. Himmel, M. E. et al. Biomass recalcitrance: engineering plants and enzymes for biofuels production. Science 315, 804–807 (2007).

    CAS  Article  PubMed  Google Scholar 

  65. Bao, W. & Renganathan, V. Cellobiose oxidase of Phanerochaete chrysosporium enhances crystalline cellulose degradation by cellulases, FEBS Lett. 302, 77–80 (1992).

    CAS  Article  PubMed  Google Scholar 

  66. Ayers, A. R., Ayers, S. B. & Eriksson, K.-E. Cellobiose oxidase, purification and partial characterization of a hemoprotein from Sporotrichum pulverulentum. Eur. J. Biochem. 90, 171–181 (1978).

    CAS  Article  PubMed  Google Scholar 

  67. Henriksson, G., Johansson, G. & Pettersson, G. A critical review of cellobiose dehydrogenases, J. Biotechnol. 78, 93–113 (2000).

    CAS  Article  PubMed  Google Scholar 

  68. Breuil, C., Chan, M., Gilbert, M. & Saddler, J. N. Influence of β-glucosidase on the filter paper activity and hydrolysis of lignocellulosic substrates. Biores. Technol. 39, 139–142 (1992).

    CAS  Article  Google Scholar 

  69. Montalvo-Rodriguez, R. et al. Autohydrolysis of plant polysaccharides using transgenic hyperthermophilic enzymes. Biotechnol. Bioeng. 70, 151–159 (2000).

    CAS  Article  PubMed  Google Scholar 

  70. Sticklen, M. B., Dale, B. E. & Maqbool, S. B. Transgenic plants containing ligninase and cellulase which degrade lignin and cellulose to fermentable sugars. US Patent 7049485 (2006).

  71. Sticklen, M. B. Production of beta-glucosidase, hemicellulase and ligninase in E1 and FLC-cellulase-transgenic plants. US Patent 20070192900 (2007).

  72. Jeoh, T. et al. Cellulase digestibility of pretreated biomass is limited by cellulose accessibility. Biotechnol. Bioeng. 98, 112–122 (2007).

    CAS  Article  PubMed  Google Scholar 

  73. Shoseyov, O., Shani, Z. & Levy, I. Carbohydrate binding modules: biochemical properties and novel applications, Microbiol. Mol. Biol. Rev. 70, 283–295 (2006).

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  74. Xiao, Z. Z., Gao, P. J., Qu, Y. B. & Wang, T. H. Cellulose-binding domain of endoglucanase III from Trichoderma reesei disrupting the structure of cellulose, Biotechnol. Lett. 23, 711–715 (2001).

    CAS  Article  Google Scholar 

  75. Levy, I., Shani, Z. & Shoseyov, O. Modification of polysaccharides and plant cell wall by endo-1,4-β-glucanase (EGase) and cellulose binding domains (CBD). Biomol. Eng. 19, 17–30 (2002).

    CAS  Article  PubMed  Google Scholar 

  76. Festucci-Buselli, R. A., Otoni, W. C. & Joshi, C. P. Structure, and functions of cellulose synthase complexes in higher plants. Braz. J. Plant Physiol. 19, 1–13 (2007). An up-to-date review of structure and function of cellulase synthase complexes in higher plants.

    CAS  Article  Google Scholar 

  77. Ridley, B. L., O'Neill, M. A. & Mohnen, D. Pectins: structure, biosynthesis, and oligogalacturonide-related signaling. Phytochem. 57, 929–967 (2001).

    CAS  Article  Google Scholar 

  78. O'Neill, M. A., Ishii, T., Albersheim, P. & Darvill, A. G. . Rhamnogalacturonan II: structure and function of a borate cross-linked cell wall pectic polysaccharide. Annu. Rev. Plant Biol. 55, 109–139 (2004).

    CAS  Article  PubMed  Google Scholar 

  79. Ziegelhoffer, T., Raasch, J. A. & Austin-Phillips, S. Dramatic effects of truncation and sub-cellular targeting on the accumulation of recombinant microbial cellulase in tobacco. Mol. Breeding 8, 147–158 (2001).

    CAS  Article  Google Scholar 

  80. Warren, R. A. J. Microbial hydrolysis of polysaccharides. Annu. Rev. Microbiol. 50, 183–212 (1996).

    CAS  Article  PubMed  Google Scholar 

  81. D'Souza, T. M., Merritt, C. S. & Reddy, C. A. Lignin-modifying enzymes of the white rot basidiomycete Ganoderma lucidum. Appl. Environ. Microbiol. 65, 5307–5313 (1999).

    CAS  PubMed  PubMed Central  Google Scholar 

  82. Boominathan, K. & Reddy, C. A. in Handbook of Applied Mycology. 4. Fungal Biotechnology (eds Arora, D. K., Elander, R. P. & Mukerji, K. G.) 763–822 (Marcel Dekker, New York,1992).

    Google Scholar 

  83. Hatakka, A. Lignin-modifying enzymes from selected white-rot fungi: production and role in lignin degradation. FEMS Microbiol. Rev. 13, 125–135 (1994).

    CAS  Article  Google Scholar 

  84. Kirk, T. K. & Farrell, R. L. Enzymatic 'combustion': the microbial degradation of lignin. Annu. Rev. Microbiol. 41, 465–505 (1987).

    CAS  Article  PubMed  Google Scholar 

  85. Dai, Z., Hooker, B. S., Quesenberry, R. D. & Thomas, S. R. Optimization of Acidothermus cellulolyticus endoglucanase (e1) production in transgenic tobacco plants by transcriptional, post-transcription and post-translational modification. Transgenic Res. 14, 627–643 (2005).

    CAS  Article  PubMed  Google Scholar 

  86. Herbers, K., Wilke, I. & Sonnewald, U. A thermostable xylanase from Clostridium thermocellum expressed at high levels in the apoplast of transgenic tobacco has no detrimental effects and is easily purified. Nature Biotechnol. 13, 63–66 (1995).

    CAS  Article  Google Scholar 

  87. Dai, Z., Hooker, B. S., Anderson, D. B. & Thomas, S. R. Expression of Acidothermus cellulolyticus endoglucanase E1 in transgenic tobacco: biochemical characteristics and physiological effects. Transgenic Res. 9, 43–54 (2000).

    CAS  Article  PubMed  Google Scholar 

  88. Ziegelhoffer, T., Will, J. & Austin-Phillips, S. Expression of bacterial cellulase genes in transgenic alfalfa (Medicago sativa L), potato (Solanum tuberosum L) and tobacco (Nicotiana tabacum L). Mol. Breeding 5, 309–318 (1999).

    CAS  Article  Google Scholar 

  89. Dai, Z., Hooker, B. S., Quesenberry, R. D. & Gao, J. Expression of Trichoderma reesei exo-cellobiohydrolase I in transgenic tobacco leaves and calli. Appl. Biochem. Biotechnol. 77, 689–699 (1999).

    Article  PubMed  Google Scholar 

  90. Reggi, S. et al. Recombinant human acid β-glucosidase stored in tobacco seed is stable, active and taken up by human fibroblasts. Plant Mol. Biol. 57, 101–113 (2005).

    CAS  Article  PubMed  Google Scholar 

  91. Kimura, T., Mizutani, T., Sakka, K. & Ohmiya, K. Stable expression of a thermostable xylanase of Clostridium thermocellum in cultured tobacco cells. J. Biosci. Bioeng. 95, 397–400 (2003).

    CAS  Article  PubMed  Google Scholar 

  92. Yang, P. et al. Expression of xylanase with high specific activity from Streptomyces olivaceoviridis A1 in transgenic potato plants (Solanum tuberosum L). Biotechnol. Lett. 29, 659–667 (2007).

    CAS  Article  PubMed  Google Scholar 

  93. Kimura, T. et al. Molecular breeding of transgenic rice expressing a xylanase domain of the xynA gene from Clostridium thermocellum. Appl. Microbiol. Biotechnol. 62, 374–379 (2003).

    CAS  Article  PubMed  Google Scholar 

  94. Patel, M., Johnson, J. S., Brettell, R. I. S., Jacobsen, J. & Xue, G. P. Transgenic barley expressing a fungal xylanase gene in the endosperm of the developing grains. Mol. Breeding 6, 113–124 (2000).

    CAS  Article  Google Scholar 

  95. Biswas, G. C. G., Ransom, C. & Sticklen, M. Expression of biologically active Acidothermus cellulolyticus endoglucanase in transgenic maize plants. Plant Sci. 171, 617–623 (2006).

    CAS  Article  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Related links

Related links

FURTHER INFORMATION

Mariam Sticklen's homepage

Joint Genome Institute

Glossary

Antisense oligonucleotides

Short synthetic pieces of DNA that are designed to bind to their target mRNA through base pairing. As a result, they inhibit the expression of the target mRNA, causing inhibition of translation, splicing or transport of the target mRNA, or degradation of the DNA–RNA hybrid by RNase H.

RNA interference

In RNAi, long double-stranded RNAs (dsRNAs of around >200 nt) are used to silence the expression of specific target genes. Long dsRNAs are first processed into 20–25 nt small interfering RNAs (siRNAs) by the Dicer RNase III-like enzyme. SiRNAs then assemble into endoribonuclease-containing RNA-induced silencing complexes (RISCs), and subsequently guide RISCs to complementary RNA molecules, which they cleave and destroy.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Sticklen, M. Plant genetic engineering for biofuel production: towards affordable cellulosic ethanol. Nat Rev Genet 9, 433–443 (2008). https://doi.org/10.1038/nrg2336

Download citation

  • Issue Date:

  • DOI: https://doi.org/10.1038/nrg2336

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing