Regulation of secondary cell wall biosynthesis by a NAC transcription factor from .

Cell wall recalcitrance is a major limitation for the sustainable exploitation of lignocellulosic biomass as a renewable resource. Species and hybrids of the genus have emerged as candidate crops for the production of lignocellulosic feedstock in temperate climates, and dedicated efforts are underway to improve biomass yield. However, nothing is known about the molecular players involved in cell wall biosynthesis to facilitate breeding efforts towards tailored biomass. Here, we identify a transcription factor related to SECONDARY WALL-ASSOCIATED NAC DOMAIN1 (SND1), which acts as a master switch for the regulation of secondary cell wall formation and lignin biosynthesis. Ms is expressed in growth stages associated with secondary cell wall formation, together with its potential targets. Consistent with this observation, Ms was able to complement the secondary cell wall defects of the double mutant, and ectopic expression of Ms in tobacco leaves was sufficient to trigger patterned deposition of cellulose, hemicellulose, and lignin reminiscent of xylem elements. Transgenic studies in plants revealed that MsSND1 regulates, directly and indirectly, the expression of a broad range of genes involved in secondary cell wall formation, including MYB transcription factors which regulate only a subset of the SCW differentiation program. Together, our findings suggest that MsSND1 is a transcriptional master regulator orchestrating secondary cell wall biosynthesis in .