Abstract text: Our laboratory is working on investigating the transcriptional regulation of plant cell wall remodelling, a process that remains largely unexplored. We selected Arabidopsis MYB46, a tier-2 transcription factor, to elucidate its role in cell wall-related mechanisms. To pinpoint previously unidentified targets, we conducted transcriptomic analysis using 35S::MYB46 and chip-sequencing with 35S:GFP-MYB46. This combined strategy identified plasma membrane-localised GELP7 as a potential MYB46 targets, implicating its role in modulating polysaccharide acetylation. Transactivation analysis indicated that MYB46 does not directly activate the GELP7 promoter; instead, activation occurs via MYB103, which also regulates the expression of the xyloglucan acetyl transferase (TBL27). This finding aligned with the observed decrease in xylan O-acetylation and increase in xyloglucan O-acetylation in 35S:MYB46 plants. Collectively, our results revealed a distinctive MYB46-MYB103 transcriptional module governing polysaccharide O-acetylation during and post-synthesis.

Additionally, we found that MYB87 expression was upregulated and MYB87 promoter was also transactivated in response to xylo-oligosaccharides with varying degrees of polymerisation. Functional studies of myb87 mutant and MYB87 gain-of-function lines showed disruption in several cell wall components. Further RNA sequencing and transactivation analyses identified several direct targets of MYB87. At present, we are elucidating the mechanism by which MYB87 mediates xylo-oligosaccharide-dependent cell wall remodelling.