ENHANCEMENT OF SORGHUM FOR BIOENERGY, FEED, AND FOOD VALUE
Location: Grain, Forage & Bioenergy Research
Title: The sorghum brown midrib mutants, tools to improve biomass for feed and bio-fuels
Submitted to: Annual International Plant & Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: January 14, 2009
Publication Date: January 10, 2009
Citation: Sattler, S.E., Saathoff, A.J., Haas, E.J., Palmer, N.A., Funnell-Harris, D.L., Sarath, G., Pedersen, J.F. 2009. The sorghum brown midrib mutants, tools to improve biomass for feed and bio-fuels. PAG XVII. Abstract W467.
Sorghum (Sorghum bicolor) serves as an important model for bioenergy crop development. brown midrib 6 and 12 (bmr-6 and -12) mutants affect phenylpropanoid metabolism resulting in reduced lignin concentrations and altered lignin composition in sorghum, which increases the conversion efficiency of biomass into bio-fuel. bmr-6 plants were shown to have reduced cinnamyl alcohol dehydrogenase (CAD; EC 18.104.22.168) activity, the final step in monolignol biosynthesis. A candidate gene approach was taken to identify the bmr-6 mutation, and a nonsense mutation was discovered in one of the sorghum CAD genes. Phylogenetic analysis indicated that BMR-6 is a member of an evolutionarily conserved group of CAD proteins, which are known to function in lignin biosynthesis. BMR-12 was previously identified as encoding caffeic acid-O-methyltransferase (COMT). bmr-6 and bmr-12 mutants have been comprehensively characterized. Near-isogenic lines containing both mutants in addition the double mutant were constructed in three sorghum varieties; Atlas, Wheatland and Tx430. Both free and cell wall-bound phenolic compounds were analyzed from sorghum internodes. Internodes were also examined by histochemical staining for lignin. The CAD and COMT proteins were characterized in heterologous expression system and through immunoblots. Together these data demonstrate the impact bmr-6 and bmr-12 have on lignin composition, cell wall architecture and plant physiology across three distinct genetic backgrounds. These data underscore CAD and COMT genes as targets for improving bioenergy crops.