Reports

The evolutionary emergence of lignin, a phenolic polymer deposited in the secondary cell wall, allowed the development of vascular land plants. The hydrophobic and strengthening nature of lignin enables conducting xylem vessels to transport water and nutrients from the roots to photo-synthetic organs while withstanding the negative pressure caused by transpiration (1, 2). The strengthening of fiber cells by lignification al-lows vascular plants to grow tall and stand upright (1, 3, 4). However, these very same physicochemical properties of lignin are a barrier to the isolation of cellulose fibers by chemical pulping and the enzymatic hy-drolysis of cell wall polysaccharides in biorefining. Biomass feedstocks with less lignin or with more degradable lignin would reduce the high processing costs and carbon footprint of paper, biofuels and chemicals (5). The lignin biosynthetic pathway has been extensively studied (6– 10). In dicotyledenous plants, lignin is mainly synthesized from tw