ISOLATION AND CHARACTERISATION OF LIGNIN BIOSYNTHESIS GENES FROM FORAGE GRASSES

Plant Biotechnology Centre, Agriculture Victoria, La Trobe University and CRC for Molecular Plant Breeding, Bundoora, Victoria 3083, Australia

Lignification of plant cell walls is a major factor identified as responsible for lowering digestibility of forage tissues as they mature. Our research is aimed at modifying the lignin profile of forage grasses for improved digestibility by down-regulating, through antisense and sense suppression in transgenic plants, the expression of genes encoding key enzymes involved in biosynthesis of monolignols. Perennial ryegrass (Lolium perenne L.) cDNA libraries were screened for the isolation of genes involved in lignin biosynthesis. Full length cDNA clones encoding caffeic acid O-methyltransferase (LpOMT1, LpOMT2 and LpOMT3), 4-coumarate-coenzyme A ligase (Lp4CL1, Lp4CL2 and Lp4CL3), cinnamoyl CoA reductase (LpCCR1) and cinnamyl-alcohol dehydrogenase (LpCAD1 and LpCAD2) perennial ryegrass homologues were obtained and sequenced. Expression patterns and gene organization were analyzed. Transformation vectors using constitutive and xylem-specific promoters were generated and transgenic plants produced for the functional analyses of these lignin biosynthesis genes. This will enhance our understanding of lignin biosynthesis, monomeric composition and properties in grasses, and will facilitate the production of forage grasses with manipulated lignification and enhanced herbage quality.