The RcDREB1E-RcMYB28 module improves drought tolerance in Rosa chinensis via RcLAR/RcCORA1-mediated proanthocyanidin biosynthesis and stress responses.

Drought is widely recognized as one of the most severe abiotic stresses limiting plant growth and productivity. Proanthocyanidins (PAs), as key functional secondary metabolites, are central to enhancing plant tolerance to abiotic stresses. Nevertheless, the specific mechanisms underlying PA-mediated drought resistance in rose remain largely unclear. Herein, we demonstrate that drought-induced PA accumulation constitutes a conserved evolutionary mechanism across the plant kingdom, ranging from unicellular algae to angiosperms. Specifically, according to the drought-responsive transcriptome dataset of Rosa chinensis 'Old Blush', an R2R3-MYB transcription factor, RcMYB28, was identified. Overexpression of RcMYB28 remarkably enhanced drought tolerance and induced a significant increase in PAs accumulation, whereas plants with silenced RcMYB28 displayed the opposite phenotypic characteristics. Specifically, RcMYB28 directly regulated the expression of leucoanthocyanidin reductase (RcLAR) and a cold and drought regulatory-protein encoding gene (RcCORA1), thereby promoting PA synthesis and enhancing the stress response. Moreover, we identified RcDREB1E as a potential upstream transcriptional regulator of RcMYB28. RcDREB1E exerts a positive regulatory effect on drought tolerance and PAs accumulation via RcMYB28 expression. Collectively, our results demonstrate a new transcriptional regulatory module (RcDREB1E-RcMYB28) underlying drought-triggered PAs accumulation, which offers valuable genetic resources for engineering enhanced drought tolerance in rose.