The MYB transcription factor ClPC modulates petal color and chlorophyll accumulation in watermelon

During the pre-anthesis stage, high chlorophyll levels in petals result in a green hue in many plants. Upon anthesis, chlorophyll degradation uncovers other pigments, thereby influencing pollinator attraction and reproductive success in insect-pollinated crops. In the watermelon accession WM109, a novel petal phenotype characterized by a yellow-green hue was observed, significantly different from the canonical yellow petal phenotype typically associated with this species. Genetic analysis using F₂ populations revealed that this yellow-green petal trait is controlled by a single recessive gene. By screening SSR primer pairs with the constructed yellow and yellow-green DNA pools and genotyping F₂ individuals, the responsible gene was mapped to a 139.7 kb interval on watermelon chromosome 11, containing two candidate genes. Through sequence analysis, expression profiling, and functional verification of these candidates, a gene encoding a MYB transcription factor with a base insertion was identified as the key determinant of this unusual phenotype, which is characterized by elevated chlorophyll levels and increased chloroplast density. Given the limited current knowledge regarding the relationship between MYB transcription factors and chlorophyll biosynthesis, these findings enhance our understanding of the molecular mechanisms underlying chlorophyll production.