Hydrogen-rich water maintains the quality of Rosa roxburghii by regulating AsA biosynthesis and regeneration

Rosa roxburghii is of great interest due to its high ascorbic acid (AsA) content, however AsA is readily lost after harvest. This study aimed to explore the effect of hydrogen-rich water (HRW) treatment on AsA metabolism in postharvest R. roxburghii. Results showed that HRW treatment maintained fruit quality and higher AsA content of R. roxburghii during the assay period. HRW treatment up-regulated the expression of AsA synthesis-related genes such as RrGMP, RrGME, RrGGP, RrGalDH, RrGalLDH and RrGalUR, but barely regulated the expression of RrGPP and RrMIOX. HRW promoted the activity and gene expression of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) in the AsA-GSH cycle. More interestingly, seven RrMYBs were significantly upregulated by HRW treatment and their expression trends were highly correlated with AsA content, suggesting that RrMYBs might transcriptionally regulate AsA synthesis and regeneration in postharvest. Our results emphasized that HRW reduced AsA loss, and positively regulated the expression of numerous AsA synthesis and regeneration genes and RrMYBs, thus illustrating a close link between RrMYBs and AsA synthesis and regeneration in postharvest R. roxburghii fruit.