Changes in Cell Wall Carbohydrate Extractability Are Correlated with Reduced Recalcitrance of HCT Downregulated Alfalfa Biomass

Abstract

Downregulation of the expression of enzymes involved in lignin biosynthesis in alfalfa (Medicago sativa L.) has been shown to result in reduced cell wall recalcitrance and increased saccharification. Here we describe changes in the extractability of hemicellulosic and pectic polysaccharides in cell walls of alfalfa downregulated in the expression of hydroxycinnamoyl CoA:shikimate hydroxycinnamoyl transferase (HCT). Xylan and pectic polysaccharides are more readily solubilized from the cell walls of HCT downregulated transgenic lines than from empty vector control plants, suggesting alterations in lignin-polysaccharide interactions in the transgenic plants. Our studies show that reduced recalcitrance of HCT downregulated lines is also correlated with increased xylan extractability.