Mapping of CaPP2C35 involved in the formation of light-green immature pepper (Capsicum annuum L.) fruits via GWAS and BSA

Abstract

Genome-wide association study, bulked segregant analysis, and genetic analysis delimited the LG locus controlling light-green immature pepper fruits into a 35.07 kbp region on chromosome 10. A strong candidate gene, CaPP2C35, was identified in this region. In pepper (Capsicum annuum L.), the common colors of immature fruits are yellowish white, milky yellow, green, purple, and purplish black. Genes related to dark green, white, and purple immature fruits have been cloned; however, only a few studies have investigated light-green immature fruits. Here, we performed a genetic study using light-green (17C827) and green (17C658) immature fruits. The light-green color of immature fruits was controlled by a single locus-dominant genetic trait compared with the green color of immature fruits. We also performed a genome-wide association study and bulked segregant analysis of immature-fruit color and mapped the LG locus to a 35.07 kbp region on chromosome 10. Only one gene, Capana10g001710, was found in this region. A G-A substitution occurred at the 313th base of the Capana10g001710 coding sequence in 17C827, resulting in the conversion of the α-helix of its encoded PP2C35 protein into a β-fold. The expression of Capana10g001710 (termed CaPP2C35) in 17C827 was significantly higher than in 17C658. Silencing CaPP2C35 in 17C827 resulted in an increase in chlorophyll content in the exocarp and the appearance of green stripes on the surface of the fruit. These results indicate that CaPP2C35 may be involved in the formation of light-green immature fruits by regulating the accumulation of chlorophyll content in the exocarp. Thus, these findings lay the foundation for further studies and genetic improvement of immature-fruit color in pepper.