Identification and characterization of <i>CsYP</i> in regulating chloroplast development and cucumber peel color

Abstract 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.