Regulation of polyphenolics and genetic manipulation of lignins in grasses

For fermentation, pyrolysis based transport fuel applications, and possibly gasification, a reduction in lignin levels or altered lignin structures and distributions within the plant will enhance the value of grasses entering industrial processes; whereas for combustion applications, increased lignin levels and high calorific value would be desirable. We have established technologies for monitoring lignin and phenolic acids in natural, mutant and transgenic populations of forages and have been extending this to energy crops including Miscanthus. Brown midrib (bmr) mutants of maize are known to have modified lignin structure and exhibit increased digestibility and we have shown that these mutants show higher rates of enzyme mediated sugar release than control plants. As such it may be predicted that the lignocellulose fraction of bmr mutants of Miscanthus may be more amenable to both enzymic release of cell wall sugars by fermentation or for production of high quality bio-oils via pyrolysis. Characterised bmr mutants occur in the CAD and OMT genes of the lignin biosynthetic pathway and opportunities exist for generating bmr mutants in Miscanthus by down-regulation of CAD and OMT gene expression. The CAD gene has been cloned in Miscanthus and is being used in an RNAi experiment in Miscanthus to mis-express the gene.