The gibberellins and RhMYB70 feedback loop fine-tunes the cell expansion and petal size in rose plants

Cell expansion of petals plays a crucial role in flower opening in rose plants. Silencing of RhMYB70 leads to a lager petal size and cell size than TRV control. RhMYB70 could directly interact with Cellulose Synthase gene RhCESA8 promoter and repress its transcription. In addition, we identified another RhMYB70-target GA biosynthesis gene RhGA20ox by transcriptome analysis and RhMYB70 could directly bind to and inhibit the promoter activity of RhGA20ox. Besides, knocking down of RhMYB70 resulted in increased GA1 and GA3 levels in petals compared to TRV at stage 3. Together, our finding revealed that the feedback of GA and RhMYB70 fine-tunes the petal size by governing the cell expansion, providing vital gene pool for improving the flower quality in rose plants.