|Walbot, Virginia - STANFORD UNIVERSITY|
Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 16, 2007
Publication Date: July 27, 2007
Citation: Lawrence, C.J., Walbot, V. 2007. Translational Genomics for Bioenergy Production from Fuelstock Grasses: Maize as the Model Species. The Plant Cell. 19(7):2091-2094. Interpretive Summary: Leveraging insights from model organisms for applied purposes uses basic genetic findings to solve practical problems; this practice has evolved into the field called ‘translational genomics.’ Here, maize is supported as the appropriate model plant for scientific study of biofuel production in the closely related fuelstock grasses. Understanding cellulosic biofuel production in maize will enable scientists to improve switchgrass and E-grass for biofuel production.
Technical Abstract: Meeting U.S. and world energy needs using biofuels rests on our ability to improve grasses that use the efficient C4 photosynthetic pathway in which carbon dioxide concentrating mechanisms sustain high biomass production, particularly when water is limiting. Today two C4 grasses yield substantial ethanol: tropical sugarcane juice (Saccharum officinalis) and U.S. corn starch (Zea mays spp. mays) converted to sugar. Ethanol from U.S. corn is government-subsidized and only a short-term solution to replacing petroleum and coal for two reasons. Diverting food for fuel is difficult to justify in a world with hungry people, and starch contains less energy than inedible plant products such as wood chips, corn leaves, and grass clippings. The better solution is new energy crops and new technology for converting sugar polymerized in cellulose and other plant cell wall polymers into ethanol or biodiesel by enzymes from wood-digesting microbes, such as termite symbionts. Two temperate zone grasses are proposed as U.S. biofuel crops: E-grass (the perennial sterile hybrid between Miscanthus sinensis and M. sacchariflorus) and perennial switchgrass (Panicum virgatum). E-grass and switchgrass can be grown on land unsuitable for corn and soybean farming in the Midwest, averting displacing food production for fuel. To speed improvement of these undomesticated grasses, three model species are discussed as the "lab rat" for basic research: rice, Brachypodium distachyon, and maize. The best feature of rice is that its 450 Mega base pairs (Mbp) genome has been completely sequenced. Brachypodium also has a small genome (~355 Mbp) and is readily grown in the lab. The limitation to these species is that they lack the physiologically unique and highly efficient C4 pathway for photosynthesis and are distantly related to the proposed energy feedstocks. Many researchers new to biofuel research disparage maize, mainly to emphasize the future of E-grass and switchgrass. But, unlike rice and Brachypodium, maize is a C4 grass closely related to both E-grass and switchgrass. It can serve as an ideal model, not only in the lab but also for translational research.