CmERFV-2 regulates CmCBF3 and CmMYB44 to inhibit sucrose accumulation in oriental melon fruit at low temperature

Low temperature is involved in regulating plant growth, development, and quality formation. The mechanism by which low temperature affects sucrose accumulation in oriental melon fruit is currently unclear. Here, high-sucrose (HS) melons were used as the research materials and subjected to two temperature regimes of 30℃/18℃ (day/night) and 22℃/10℃ (day/night) at the onset of ethylene production. Low temperature significantly inhibited ethylene release and sucrose accumulation in melon fruit, while ethephon treatment at low temperature partially restored the ethylene production and sucrose content. Using yeast one-hybrid (Y1H), GUS activity analysis, and luciferase assay, we found that the transcription factor CmCBF3 could bind to CmACO1 (ACC oxidase 1) promoter and inhibit its activity, thereby suppressing ethylene production. Overexpression of CmCBF3 under low temperature significantly inhibited the synthesis of ethylene and sucrose. Further research showed that low temperature promoted CmERFV-2 expression, and CmERFV-2 could bind to CmCBF3 promoter to further inhibit ethylene synthesis. In addition, CmMYB44, a transcription factor that negatively regulated fruit ethylene production and sucrose accumulation, repressed the expression of CmACO1 and CmSPS1 (sucrose phosphate synthase 1). CmERFV-2 further affected the expression of CmACO1 and CmSPS1 by binding to CmMYB44 promoter, thereby regulating ethylene and sucrose content at low temperature. In summary, this study revealed the mechanism by which CmERFV-2 affects ethylene release and sucrose accumulation in oriental melon fruit, laying a foundation for breeding high-quality melon varieties suitable for low-temperature cultivation.