CmMYB113 and CmMADS26 interact to regulate ethylene synthesis and sucrose accumulation in oriental melon fruit

Sugar content is one of significant marks of fruit quality, and understanding the regulatory mechanism of sucrose accumulation is fundamental for breeding excellent melon fruit. As indicated by the co-expression network analysis, we distinguished a MYB transcription factor, CmMYB113, whose expression responds to oriental melon ('HS' (high-sucrose cultivar) and 'LW' (low-sucrose cultivar)) fruit ripening. Agrobacterium-mediated transient transformation injection and stable genetic transformation system confirmed that CmMYB113 promoted the sucrose accumulation and ethylene synthesis by up-regulating the expression of CmACO1 and CmSPS1 in oriental melon fruit. What's more, we also identified a MADS transcription factor from the transcriptome, CmMADS26, which is highly expressed during melon fruit ripening. Intriguingly, CmMADS26 could directly bind to the promoter of CmACO1 to promote its transcription, and CmMYB113 physically interacted with CmMADS26 in yeast and tobacco leaves. Our findings give new bits of knowledge into the regulatory mechanisms by which MYB and MADS transcription factors interact to regulate melon fruit ripening and sucrose accumulation. Overall design: To investigate the molecular mechanism of sucrose accumulation differences in oriental melon fruit of different varieties, RNA-seq was performed on samples from four developmental stages of two oriental melon varieties to screen differentially expressed genes and transcription factors