Identification and characterization of CsYP in regulating chloroplast development and cucumber peel color

Skin color is a crucial quality trait in cucumber fruit, yet the regulatory mechanisms underlying cucumber skin color remain poorly understood. In this study, we characterized a cucumber natural mutant displaying yellow peel, and identified a key gene yellow peel (CsYP) through map-based cloning. CsYP encodes a rhodanese-like protein with a Rhod domain. A single-base insertion results in premature termination of protein translation, leading to the yellowing pericarp phenotype in the natural mutant. To further investigate the function of CsYP, two knockout lines, yp-1 and yp-2, were generated using CRISPR-Cas9 technology. Phenotypic investigation of yp-1 and yp-2 revealed a significant yellowing of the pericarp starting from 6 days after pollination, consistent with the natural mutant phenotype. Additionally, our study revealed an interaction between CsYP and Cscytb6f, a cytochrome b6-f complex iron-sulfur subunit, suggesting a collaborative role of CsYP and iron-sulfur proteins in regulating cucumber peel color. These findings provide novel insights into the regulatory mechanisms underlying cucumber peel color and broaden our understanding of this important trait.