PagMYB216 is involved in the regulation of cellulose synthesis in Populus

Cellulose accounts for most of the structural material in secondary cell walls. Although the synthesis of cellulose has been extensively investigated, the regulation of cellulose synthesis in woody plants remains elusive. In this study, we showed PagMYB216 to be involved in the regulation of cellulose synthesis in Populus. Subcellular localization and transcriptional activation analyses suggest that PagMYB216 is a nuclear-localized transcriptional activator. Transient transcriptional assays revealed that PagMYB216 could activate the expression of secondary cell wall cellulose synthesis genes (CESAs) through binding to the GAMYB motif. Overexpression of PagMYB216 in Populus resulted in enhanced expression of secondary wall CESAs and increased cellulose content in stems. In contrast, the dominant repression of PagMYB216 transgenic poplar plants led to the downregulation of secondary wall CESAs and decreased cellulose content. In addition, cellulose deposition and secondary wall thickness were increased in stems from PagMYB216 overexpression poplar plants and decreased in stems from PagMYB216 dominant repression poplar plants. Taken together, our results suggest that PagMYB216 is involved in the modulation of cellulose synthesis in Populus by controlling the expression of secondary wall CESAs.