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.

中文翻译：

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控制南瓜白色花瓣颜色表型的基因 Cmowf 的遗传分析和表征（Cucurbita moschata D）

花色作为重要的形态标记，对于提高杂交生产中种子纯度的鉴定效率具有重要作用。然而，南瓜( Cucurbita moschata D.)白花性状的分子机制尚未见报道。在本研究中，我们通过对自交系N87（黄花）进行甲磺酸乙酯（EMS）诱变获得了白花突变体（wf ）。然后通过将wf突变体和 N87 植物杂交构建 F2 群体，以精细定位控制南瓜白花性状的基因。表型鉴定表明，与N87植株相比，wf突变体花瓣中类胡萝卜素含量显着降低。遗传分析表明白花突变体性状由单个隐性基因Cmowf控制。使用批量分离分析和 KASP 表型分析，Cmowf被定位到 14 号染色体上包含三个注释基因的 762 kb 区域。其中，仅在编码DUF1997家族蛋白的CmoCh14G005820基因中发现非同义单核苷酸多态性突变。与wf突变体和N87植物之间的CmoDUF1997氨基酸序列相比， wf突变体中发生了关键氨基酸突变（氨基酸提前终止），因此预测CmoCh14G005820是控制白花性状的潜在候选者。 RNA测序分析显示，在wf突变体中， CmoCh14G005820和大多数参与类胡萝卜素生物合成的基因的表达显着下调，而负责类胡萝卜素降解的几个基因的表达在wf突变体中上调。这一发现表明类胡萝卜素代谢可能参与了南瓜花色的形成。总的来说，我们的结果为理解南瓜白花形成的遗传机制提供了理论基础。