The transcription factor CsAPRR2 controls peel color by regulating the expression of SULFURTRANSFERASE14 in cucumber

Peel color is an important trait that determines the appearance and quality of cucumber (Cucumis sativus L) fruits. Several genes controlling peel color have been identified, but the mechanism of their involvement in peel color regulation is still unclear. Here, we examined the genetics of the yellow peel using a segregating population derived from a cross between 6101-11 and 6101-12. We identified Arabidopsis pseudo-response regulator 2 (CsAPRR2) as a candidate gene for controlling peel color. CRISPR-Cas9 analysis confirmed that the loss of CsAPRR2 function resulted in abnormal chloroplast structure and yellowing phenotype. RNA-seq and DAP-seq analysis revealed that CsAPRR2 can directly bind to the promoter of Sulfurtransferase 14 (CsSTR14) and activate its expression. It is worth noting that csaprr2 can still bind to CsSTR14, but the activation ability of csaprr2 on CsSTR14 is significantly weakened. These results suggest that CsSTR14 may be involved in the transport of sulfur in cucumber peel to control peel color. Collectively, our results reveal the biological function of CsAPRR2 in cucumber and the mechanism by which CsAPRR2 may regulate peel color by affecting sulfur transport. This finding opens a research direction for regulating chloroplast development through sulfur metabolism.