Genetic analysis and characterisation of Cmowf, a gene controlling the white petal colour phenotype in pumpkin (Cucurbita moschata D)

Abstract

Flower colour, as an important morphological marker, plays an essential role in improving the identification efficiency of the purity seed in hybrid production. However, the molecular mechanism of white‐flower trait has not been reported in pumpkin (Cucurbita moschata D.). In this study, we obtained a white‐flower mutant (wf) through the ethyl methane sulfonate (EMS) mutagenesis of inbred line N87 (yellow flower). F2 populations were then constructed by crossing wf mutant and N87 plant to fine map the genes controlling white‐flower trait in pumpkin. Phenotypic identification revealed that carotenoid content significantly decreased in the petals of wf mutants compared with N87 plants. Genetic analysis indicated that the white flower mutant trait was controlled by a single recessive gene, Cmowf. Using bulked segregant analysis and KASP phenotyping, Cmowf was mapped to a 762 kb region on chromosome 14 containing three annotated genes. Among them, a nonsynonymous single‐nucleotide polymorphisms mutation was identified only in CmoCh14G005820 gene, which encoded a DUF1997 family protein. Compared with CmoDUF1997 amino acid sequences between the wf mutants and N87 plants, the critical amino acid mutations (early termination of amino acids) occurred in wf mutants, so CmoCh14G005820 was predicted as a potential candidate for controlling the white‐flower trait. RNA‐sequencing analysis revealed that the expression of CmoCh14G005820 and most genes involved in carotenoid biosynthesis was significantly downregulated in wf mutants, whereas the expression of several genes responsible for carotenoid degradation was upregulated in wf mutants. This finding suggested that carotenoid metabolism may participate in the formation of flower colour in pumpkin. Overall, our results provided a theoretical basis for understanding the genetic mechanisms underlying white‐flower formation in pumpkin.