Genetic Mapping and Identification of the Gibberellin 3-Oxidase Gene GA3ox Leading to a GA-Deficient Dwarf Phenotype in Pumpkin (Cucurbita moschata D.)

Abstract

Plant height is an important indicator in the ideal plant model and contributes to optimizing yield and lodging resistance. The emergence of a dwarfing phenotype provides an opportunity for plant height improvement. In a previous study, we identified a dwarf mutant Si1 in pumpkin (Cucurbita moschata D.) obtained by ethyl methane sulfonate (EMS) mutagenesis of the inbred line N87. Phenotype identification for Si1 revealed a decrease in cell size and shorter internodes than those of wild type. Genetic analysis revealed that the dwarf mutant trait was controlled by a single recessive gene, CmaSI1. By bulked segregant analysis (BSA) and subsequent fine mapping, we mapped the CmaSI1 locus to a 463 kb region on chromosome 8 that contained 28 annotated genes in the F2 population. Only one nonsynonymous single nucleotide polymorphism (SNP) in CmoCh08G006170 was obtained according to whole-genome resequencing of the two parents. CmoCh08G006170, a homolog of Arabidopsis gibberellin 3-beta hydroxylase (GA3ox), is a key enzyme in the regulation of bioactive gibberellins (GAs). RNA-seq analysis and qRT-PCR showed that the expression level of CmoCh08G006170 in stems of Si1 was changed compared with that of wild type. The dwarf phenotype could be restored by exogenous GA3 treatment, suggesting that Si1 is a GA-deficient mutant. The above results demonstrated that CmoCh08G006170 may be the candidate gene controlling the dwarf phenotype. This study provides an important theoretical basis for the genetic regulation of vine length and crop breeding in pumpkin.

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

“…wf was screened in the M2 generation population of the pumpkin mutant library that we had established earlier (Min et al, 2022). Throughout the entire flower development, wf had white‐flowered petals, which differed from the yellow‐flowered petals of wild‐type N87 plants (Figure 1a).…”

“…Accordingly, a foundation is laid to better understand the regulatory mechanisms of flower‐colour formation in tree peony plants. Similarly, Min et al (2022) combined BSA‐Seq and RNA‐Seq analyses to investigate genes that control a dwarfing phenotype in pumpkin mutant, and CmoCh08G006170 is determined as the most likely candidate gene. In the present study, RNA‐Seq analysis showed that the DEGs were highly enriched in carotenoid biosynthesis and degradation pathways, and the expression of CmoCh14G005820 was downregulated in petals of wf .…”

“…A white‐flower mutant ( wf ) in pumpkin was identified in an EMS mutagenised population of the high‐generation pumpkin inbred line N87 (Min et al, 2022). A hybridisation between the two parental lines, N87 (P1) and wf (P2), was used to produce hybrid F1, and then one F1 plant was self‐pollinated to generate the F2 population.…”

“…The method of KASP genotyping was in accordance with previously described studies (Hao et al, 2018; Min et al, 2022). SNP molecular markers were designed in the candidate region according to the re‐sequenced DNA and were polymorphic between wf and N87.…”

“…wf was screened in the M2 generation population of the pumpkin mutant library that we had established earlier (Min et al, 2022).…”