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Thermocycle-regulated WALL REGULATOR INTERACTING bHLH Encodes a Protein That Interacts with Secondary-Cell-Wall-Associated Transcription Factors

Lignocellulosic biomass is one of the most abundant raw materials on earth that can be utilized to created carbon-neutral biofuels as a replacement for conventional fossil fuels. In order to create ideal energy crops, the regulation and deposition of cell wall polysaccharides must first be fully understood. Improved understanding of cell wall regulation will enable selection of traits that can optimize biofuel feedstocks. Herein, I utilize the grass model system Brachypodium distachyon in order to understand the transcriptional regulation of secondary cell wall deposition. Gene expression profiling was used to elucidate transcription factors that regulate secondary cell wall biosynthesis. Through this method, WALL REGULATOR INTERACTING bHLH (WRIB) was identified and its role as a secondary cell wall regulator was tested. Yeast-one- and yeast-two-hybrid assays showed that WRIB is capable of binding to promoters of secondary cell wall biosynthesis genes, as well as interacting with known secondary cell wall transcription factor proteins and also Phytochrome B. These results suggest that WRIB plays an important role in the secondary cell wall regulatory network and could perhaps be modulated by Phytochrome B. Discovery of this novel and interesting gene furthers the overall understanding of secondary cell wall development with the goal of improving our ability to engineer biofuel feedstocks.