MiMYB1R1-like and MiMYB44-like transcription factors interact with MiGalDHpro to modulate ascorbic acid metabolism during ethylene-mediated mango fruit ripening.

Mango (Mangifera indica L.), a climacteric fruit, undergoes rapid ripening driven by ethylene signaling, which plays a crucial role in modulating ascorbic acid (AsA) metabolism. AsA biosynthesis is primarily governed by the L-galactose pathway, with GDP-L-galactose phosphorylase (MiGalDH) catalyzing a key step. This study investigates the transcriptional regulation of MiGalDH by MiMYB1R1-like and MiMYB44-like during ethylene-mediated ripening. Ethylene treatment accelerated ripening and significantly reduced GalDH activity, leading to a decline in AsA levels. Notably, dehydroascorbic acid (DHA) content increased toward the end of storage, suggesting enhanced AsA turnover. RNA-seq analysis revealed that ethylene upregulated MiMYB1R1-like while downregulating MiMYB44-like. Functional assays, including Y1H, EMSA and Dual-Luc analyses, confirmed that both transcription factors directly bind to the MiGalDH promoter to regulate its expression. Virus-induced gene silencing of MiMYB1R1-like and MiMYB44-like significantly reduced MiGalDH expression and AsA content but increased GalDH activity, suggesting enhanced AsA turnover to maintain redox balance. Overexpression of MiMYB1R1-like sustained GalDH activity and promoted AsA biosynthesis throughout ripening, whereas MiMYB44-like overexpression exhibited stage-specific effects-enhancing GalDH activity early but repressing it later. Overall, our findings highlight the pivotal role of MiGalDH in AsA metabolism and identify MiMYB1R1-like and MiMYB44-like as key transcription factors. This study provides novel insights into the transcriptional control of ethylene-induced ripening and AsA metabolism, offering potential targets for improving fruit quality and extending shelf life.