Fine-mapping and candidate gene analysis of the Mcgy1 locus responsible for gynoecy in bitter gourd (Momordica spp.)

Abstract

Abstract Gynoecy plays an important role in high-efficiency hybrid seed production, and gynoecious plants are excellent materials for dissecting sex differentiation in Cucurbitaceae crop species, including bitter gourd. However, the gene responsible for gynoecy in bitter gourd is unknown. Here, we first identified a gynoecy locus designated Mcgy1 using the F2 population (n=291) crossed from the gynoecious line S156G and the monoecious line K8-201 via bulked segregant analysis with whole-genome resequencing and molecular marker linkage analysis. Then, a large S156G×K8-201 F2 population (n=5,656) was used for fine-mapping to delimit the Mcgy1 locus into a 292.70-kb physical region on pseudochromosome MC01, which did not include any homologous gynoecy genes previously reported in Cucurbitaceae species. Furthermore, a novel gene, MC01g1681, which encodes a cytidine triphosphate synthase, was considered the underlying gene of Mcgy1 on the basis of the results of RNA sequencing, multiple genomic sequence variation and expression analyses. In addition, transcriptome analysis of S156G and its monoecious near-isogenic line S156 revealed the potential molecular mechanisms of the formation of gynoecy in bitter gourd. Our findings provide a new insight into inheritance modes of gynoecious plants in Cucurbitaceae species and a theoretical basis for breeding gynoecious bitter gourd lines by the use of molecular markers.