Sex determination evolved to control the development of unisexual flowers. In agriculture, it conditions how plants are cultivated and bred. We investigated how female flowers develop in monoecious cucurbits. We discovered in melon, Cucumis melo, a mechanism in which ethylene produced in the carpel is perceived in the stamen primordia through spatially differentially expressed ethylene receptors. Subsequently, the CmEIN3/CmEIL1 ethylene signalling module, in stamen primordia, activates the expression of CmHB40, a transcription factor that downregulates genes required for stamen development and upregulates genes associated with organ senescence. Investigation of melon genetic biodiversity revealed a haplotype, originating in Africa, altered in EIN3/EIL1 binding to CmHB40 promoter and associated with bisexual flower development. In contrast to other bisexual mutants in cucurbits, CmHB40 mutations do not alter fruit shape. By disentangling fruit shape and sex-determination pathways, our work opens up new avenues in plant breeding.

性别决定的进化是为了控制单性花的发育。在农业中，它决定了植物的种植和培育方式。我们研究了雌雄同株的葫芦科植物雌花是如何发育的。我们在甜瓜（Cucumis melo）中发现了一种机制，其中心皮中产生的乙烯通过空间差异表达的乙烯受体在雄蕊原基中被感知。随后，雄蕊原基中的 CmEIN3/CmEIL1 乙烯信号模块激活CmHB40 的表达，CmHB40是一种转录因子，可下调雄蕊发育所需的基因并上调与器官衰老相关的基因。对甜瓜遗传多样性的调查揭示了一种起源于非洲的单倍型，其 EIN3/EIL1 与CmHB40启动子的结合发生了改变，并与两性花发育相关。与葫芦科其他双性突变体相比，CmHB40突变不会改变果实形状。通过解开果实形状和性别决定途径，我们的工作开辟了植物育种的新途径。