Grass biomass is comprised chiefly of secondary walls that surround fiber and xylem cells. A regulatory network of interacting transcription factors in part regulates cell wall thickening. We identified Brachypodium distachyon SECONDARY WALL ASSOCIATED MYB1 (SWAM1) as a potential regulator of secondary cell wall biosynthesis based on gene expression, phylogeny, and transgenic plant phenotypes. SWAM1 interacts with cellulose and lignin gene promoters with preferential binding to AC-rich sequence motifs commonly found in the promoters of cell wall-related genes. SWAM1 over-expression (SWAM-OE) lines had greater above-ground biomass with only a slight change in flowering time while SWAM1 dominant repressor (SWAM1-DR) plants were severely dwarfed with a striking reduction in lignin of schlerenchyma fibers and stem epidermal cell length. Cellulose, hemicellulose, and lignin genes were significantly down-regulated in SWAM1-DR plants and up-regulated in SWAM1-OE plants. There was no reduction in bioconversion yield in SWAM1-OE lines; however, it was significantly increased for SWAM1-DR samples. Phylogenetic and syntenic analyses strongly suggest that the SWAM1 clade was present in the last common ancestor between eudicots and grasses, but is not in the Brassicaceae. Collectively, these data suggest that SWAM1 is a transcriptional activator of secondary cell wall thickening and biomass accumulation in B. distachyon. This article is protected by copyright. All rights reserved.
Figure 6. Rapamycin stimulates autophagy and reverses the neuroprotective effect of OXA. (A) Western blot images of LC3B and p62 and results of quantitative analysis in each group. (B) OXA attenuates the hemin-induced decrease in cell viability, while aggravated it after rapamycin administration. (C) Representative FCM plots of Annexin V-FITC apoptosis detection assay showed that autophagy activator increased apoptosis rate, and reversed the neuroprotective effect of OXA. (D) Quantified results of the flow cytometric analysis. ***p < 0.001 vs. the control group; *p < 0.05, ****p < 0.0001 vs. the hemin group; #p < 0.05, ####p < 0.0001 vs. the hemin + OXA group. 2b1af7f3a8