The sex-control system involves several mechanisms in melon. The present study identified a novel bisexual flower control gene from the hermaphroditic melon germplasm, different from the previously recognized one. Genetic analysis showed that a single recessive gene in the newly identified locus b controlled the bisexual flower phenotype in melons. We generated 1431 F₂ segregating individuals for genetic mapping of locus b, which was delimited to a 47.94 kb region. Six candidate genes were identified in the delimited interval, and candidate No. 4 encoding melon CPR5 protein was selected as the suitable one for locus b and was denoted CmCPR5. CPR5 reportedly interacted with ethylene receptor ETR1 to regulate ethylene signal transduction. Moreover, the ethephon assays showed that the parental lines (unisexual line and bisexual line) had contrasting expression patterns of CmCPR5. The BiFC and LCI assays also confirmed that CmCPR5 interacted with CmETR1 in 0426 but not in Y101. However, crossover tests showed that CmETR1 functioned normally in both parental lines, suggesting CPR5 malfunction in Y101. This study proposed a corollary mechanism of bisexual flower regulation during stamen primordium development in which the inhibition of stamen primordia development was prevented by the malfunctioning CmCPR5, resulting in bisexual flowers.

中文翻译：

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新型双性恋花控制基因调控甜瓜 (Cucumis melo L.) 的性别分化

性控制系统涉及甜瓜的几种机制。本研究从雌雄同体的甜瓜种质中鉴定出一种新的双性恋花控制基因，与之前公认的基因不同。遗传分析表明，新发现的基因座b中的一个隐性基因控制着甜瓜的双性花表型。我们生成了 1431 F ₂分离个体用于基因座b的遗传作图，其被划定为 47.94 kb 区域。在划定的区间内确定了6个候选基因，并选择编码甜瓜CPR5蛋白的候选4号作为基因座b的合适基因，记为CmCPR5. 据报道，CPR5 与乙烯受体 ETR1 相互作用以调节乙烯信号转导。此外，乙烯利分析显示亲本系（单性系和双性系）具有对比鲜明的CmCPR5表达模式。BiFC 和 LCI 测定还证实 CmCPR5 在 0426 中与 CmETR1 相互作用，但在 Y101 中没有。然而，交叉测试显示 CmETR1 在两个亲本系中正常运作，表明 CPR5 在 Y101 中出现故障。本研究提出了雄蕊原基发育过程中双性花调节的必然机制，其中 CmCPR5 功能障碍阻止了雄蕊原基发育的抑制，从而产生了双性花。