Expression Profile of Sugarcane Transcription Factor Genes Involved in Lignin Biosynthesis.

Cell wall recalcitrance, which is conferred in part by lignin, is the main bottleneck in lignocellulosic ethanol production. Transcription factors (TFs) have been suggested as targets to reduce or modify lignin. Here we analysed the expression profile of nine sugarcane TFs, their relationships with genes of the monolignol biosynthesis pathway, and their effects on lignin content and composition. Our assays compared two sugarcane genotypes with different lignin contents. To identify differences between tissue types and between the top and bottom of the plant, the culm was divided into intermediary and mature internodes, and the internodes were separated into pith and rind. The expression profiles obtained for the nine TFs were rather complex, showing that not only the genotype but also the tissue type and developmental stage influenced the results. Pearson correlation analysis indicated that ShMYB58/63 was positively correlated with the syringyl/guaiacyl ratio. In addition, a Bayesian network showed predicted interactions between the TFs and genes for lignin biosynthesis that were previously reported in the literature, as well as novel interactions such as those between ShMYB58/63 and ShF5H. These findings suggest that in sugarcane culm, the differential lignin deposition between tissue types (rind and pith) and at different developmental stages is under transcriptional regulation. [ABSTRACT FROM AUTHOR]