GhMYB106_D13 coordinates cuticle biosynthesis to build the dual shields for anther protection in upland cotton

The plant cuticle acts as a crucial barrier against abiotic stresses. In this study, the vulnerable anther (van) gene on chromosome D13 was map-based cloned in upland cotton and identified as GhMYB106_D13. It was demonstrated that the differential distribution of MYB106 between D13 and A13 may represent post-polyploidization convergent evolutionary events. Transcriptome analysis, metabolic profiling, and microscopic examination of anther cuticle in GhMYB106_D13 over-expression and knockout lines revealed that GhMYB106_D13 affects the wax and cuticle biosynthesis pathway. GC-MS analysis demonstrated that the loss of GhMYB106_D13 resulted in an ~27.6% reduction in total wax load, predominantly characterized by a decrease in very-long-chain alkanes, whereas overexpression (OE) led to wax accumulation. Key genes involved in the pathway including FACR2, LACS1, HHT1, and PXG4 were found to be changed dynamically. Specifically, GhMYB106_D13 likely activates the expression of LACS1, a gene involved in wax synthesis that was downregulated in Stage-8 anthers of the Ghmyb106_D13 mutant. Meanwhile, upregulation of FACR2, CYP704B1, and HHT1 was suggested to be potentially involved in cuticle metabolism, possibly through altered 16-feruloyloxypalmitic acid (16-FA) level. Thus, GhMYB106_D13 contributes to the formation of the first protective 'shield' for the anther against external stresses. Additionally, GhMYB106_D13 participates in trichome differentiation, which constitutes a second 'shield' that encloses the petals and sequesters the anther in the bud before flowering. Overall, these findings unveil the dual function of GhMYB106_D13 in physical protection of plant propagation and offer valuable insights for future strategies aimed at improving stress tolerance in crops.