title: RNAi downregulation of three key lignin genes in sugarcane improves glucose release without reduction in sugar production.
abstract: BACKGROUND
  Sugarcane is a subtropical crop that produces large amounts of biomass annually. It is a key agricultural crop in many countries for the production of sugar and other products. Residual bagasse following sucrose extraction is currently underutilized and it has potential as a carbohydrate source for the production of biofuels. As with all lignocellulosic crops, lignin acts as a barrier to accessing the polysaccharides, and as such, is the focus of transgenic efforts. In this study, we used RNAi to individually reduce the expression of three key genes in the lignin biosynthetic pathway in sugarcane. These genes, caffeoyl-CoAO-methyltransferase (CCoAOMT), ferulate 5-hydroxylase (F5H) and caffeic acidO-methyltransferase (COMT), impact lignin content and/or composition.
  
  
  RESULTS
  For each RNAi construct, we selected three events for further analysis based on qRT-PCR results. For theCCoAOMTlines, there were no lines with a reduction in lignin content and only one line showed improved glucose release. ForF5H, no lines had reduced lignin, but one line had a significant increase in glucose release. ForCOMT, one line had reduced lignin content, and this line and another released higher levels of glucose during enzymatic hydrolysis. Two of the lines with improved glucose release (F5H-2 and COMT-2) also had reduced S:G ratios.
  
  
  CONCLUSIONS
  Along with improvements in bagasse quality for the production of lignocellulosic-based fuels, there was only one line with reduction in juice sucrose extraction, and three lines with significantly improved sucrose production, providing evidence that the alteration of sugarcane for improved lignocellulosic ethanol production can be achieved without negatively impacting sugar production and perhaps even enhancing it.
authors.affiliation: Queensland University of Technology, Brisbane, QLD 4000 Australia.
authors.forename: William P
authors.initials: WP
authors.lastname: Bewg
authors.affiliation: Department of Biology, Syracuse University, Syracuse, NY 13244 USA.
authors.forename: Charleson
authors.identifier: 0000-0001-7157-5176
authors.initials: C
authors.lastname: Poovaiah
authors.affiliation: Department of Biological Systems Engineering, University of Wisconsin, Madison, WI USA ; US Department of Energy, Great Lakes Bioenergy Research Center (GLBRC), Wisconsin Energy Institute, University of Wisconsin, Madison, WI 53726 USA.
authors.forename: Wu
authors.identifier: 0000-0002-0677-3085
authors.initials: W
authors.lastname: Lan
authors.affiliation: US Department of Energy, Great Lakes Bioenergy Research Center (GLBRC), Wisconsin Energy Institute, University of Wisconsin, Madison, WI 53726 USA ; Department of Biochemistry, University of Wisconsin, Madison, WI 53726 USA.
authors.forename: John
authors.identifier: 0000-0002-6093-4521
authors.initials: J
authors.lastname: Ralph
authors.affiliation: Department of Biology, Syracuse University, Syracuse, NY 13244 USA.
authors.forename: Heather D
authors.identifier: 0000-0002-4923-601X
authors.initials: HD
authors.lastname: Coleman
keywords: Caffeic acid O-methyltransferase; Caffeoyl-CoA O-methyltransferase; Ferulate 5-hydroxylase; Lignin biosynthesis; RNAi; Sugarcane