Fine mapping and functional validation of the candidate gene BhGA2ox3 for fruit pedicel length in wax gourd (Benincasa hispida)

Abstract

The gene regulating fruit pedicel length in wax gourd was finely mapped to a 211 kb region on chromosome 8. The major gene, Bch08G017310 (BhGA2ox3), was identified through forward genetics. Fruit pedicel length (FPL) is a crucial trait in wax gourd (Benincasa hispida) that affects fruit development and cultivation management. However, the key regulatory genes and mechanisms of FPL in wax gourds remain poorly understood. In this study, we constructed an F₂ population using wax gourd plants with long fruit pedicels (GF-7-1-1) and short fruit pedicels (YSB-1-1-2) as parents. Through BSA-seq, we initially localised the FPL candidate gene to an 8.4 Mb region on chromosome 8, which was further narrowed down to a 1.1 Mb region via linkage analysis. A large F₂ population of 2163 individuals was used to screen for recombinants, and the locus was ultimately narrowed to within a 211 kb (62,299,856-62,511,174 bp) region. Sequence and expression analyses showed that Bch08G017310 (named BhGA2ox3) is a strong candidate gene for FPL in wax gourds. It encodes gibberellin (GA) 2-beta-dioxygenase, a member of the GA 2-oxidase (GA2ox) family. Cytology showed that GA treatment significantly elongated the fruit pedicels and enlarged the cells in the plants with short fruit pedicels. Ectopic expression of BhGA2ox3 showed that BhGA2ox3 overexpression in Arabidopsis thaliana resulted in significantly shorter fruit pedicels. This study lays a theoretical foundation for the regulatory mechanism of FPL in wax gourds and molecular breeding.