Hydrogen sulfide enhances PpbHLH3-controlled sucrose accumulation in peach chilling tolerance

Chilling injury (CI) is a serious problem that restricts postharvest preservation of peach industry. Hydrogen sulfide (H₂S) treatment efficiently mitigated CI of peach, whereas the molecular mechanism of which remains elusive. In this study, results showed that H₂S treatment maintained lower internal browning index, electrolyte leakage and malondialdehyde content in comparison with control, while hypotaurine (HT, H₂S scavenger) existed with the reverse results during cold storage. Meanwhile, H₂S treatment induced higher activities and genes expression levels of sucrose synthase-synthesis (SS-s) and sucrose phosphate synthase (SPS), while suppressing lower these levels of vacuolar invertase (VIN) and neutral invertase (NI) compared to control and HT, which was concomitant with sucrose accumulation and decrease of fructose and glucose. Moreover, transcription factor PpbHLH3 was shown to respond to low temperature and H₂S treatment and located in nucleus. Results of PpbHLH3 overexpression showed that PpSPS and PpSS-s expressions were elevated, while PpVIN and PpNI expressions were weakened in peach fruit. Further investigation revealed that PpbHLH3 could activate and inhibit the expression of PpSPS and PpVIN by binding PpSPS and PpVIN promoter E-box, respectively. Consequently, these findings revealed that H₂S treatment promoted PpbHLH3-mediated sucrose accumulation by improving the gene expression and activities of SS and SPS, and inhibiting the gene expression and activities of VIN and NI, contributing to the enhancement of cold resistance in cold-stored peach fruit.