The role of MYB46 in modulating polysaccharide acetylation by mediating the transcriptional regulation of cell wall-related genes in Arabidopsis

Understanding the mechanism behind the transcriptional regulation of polysaccharide O-acetylation remains a key challenge that might be regulated through transcription factors. Our earlier work revealed the upregulation of AtGELP7 in MYB46 overexpression lines, prompting us to investigate how MYB46 transcriptionally controls AtGELP7 including other cell wall acetylation pathway genes in Arabidopsis. In MYB46 overexpression lines, we observed alteration in acetylation levels on xylan, xyloglucan and pectin in different tissue types, which suggests complex and tight regulation of acetylation homeostasis in the cell wall. Further, our transcriptomic data revealed the simultaneous upregulation of both AtGELP7 (acetyl xylan esterase) and xylan-specific TBLs (xylan O-acetyltransferases) indicating sophisticated regulation of cell wall acetylation homeostasis. Using transactivation studies in Nicotiana and pAtGELP7::GUS stable lines, we found that MYB46 enhances AtGELP7 expression probably through downstream regulators which could be either MYB103 or other MYBs. In addition, extensive cell wall analysis of MYB46 overexpression lines showed differential sugar distribution, preferably to major cell wall components such as cellulose, xyloglucan, and xylan across different tissue types of different developmental stages. Moreover, the integration of RNA-sequencing and ChIP-sequencing data uncovered previously unknown, novel probable direct gene targets of MYB46 that may be involved in polysaccharide acetylation and cell wall remodeling.