Monolignol Biosynthesis and Regulation in Grasses

Lignin is a main phenolic component of cell walls that provides plant tissues with strength and rigidness. The nature of inherent hydrophobicity and extensive cross-links with wall-bound polysaccharides makes lignin extremely recalcitrant to mechanical disruption and enzymatic degradation. Grasses encompass most of the world's economical cereal crops and fodder species that supply human society with dietary grains, fiber, and forage. Manipulation of lignin composition and structure in grasses has a major impact on the nutritional quality of animal feed and the yield of fermentable sugars generating from bulk plant biomass. As lignin in grass species displays some characteristic difference from that in dicot plants, evidences from biochemical and genetic studies have been accumulated for the understanding of the monolignol biosynthesis in grasses. Here, we summarize the advancements of the grass lignin synthesis studies, which would aid in a comprehensive understanding of the monolignol biosynthesis and regulation as well as confer implications for bioengineering strategies of cell walls in various plants.