Cucumber (Cucumis sativus L.) is a model for the study of sex differentiation in the last two decades. In cucumber, sex differentiation is mainly controlled by genetic material, but plant growth regulators can also influence or even change it. However, the effect of exogenous auxin application on cucumber sex differentiation is mostly limited in physiological level. In this study, we explored the effects of different exogenous auxin concentrations on the varieties with different mutant sex-controlling genotypes and found that there was a dosage effect of exogenous indole-3-acetic acid (IAA) on the enhancement of cucumber femaleness. Several ACC synthetase (ACS) family members could directly respond to the induction of exogenous IAA to improve endogenous ethylene synthesis, and this process can be independent on the previously identified sex-related ACC oxidase CsACO2. We further demonstrated that ENHANCER OF SHOOT REGENERATION 2 (ESR2), responding to the induction of exogenous auxin, could directly activate CsACS2 expression by combining the ERE cis-acting element regions in the promoter, and then increase endogenous ethylene content, which may induce femaleness. These findings reveal that exogenous auxin improves cucumber femaleness via inducing sex-controlling gene and promoting ethylene synthesis.

中文翻译：

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外源生长素诱导的芽再生增强剂2（ESR2）通过激活CsACS2基因增强黄瓜雌性。


黄瓜（Cucumis sativus L.）是近二十年来研究性别分化的模型。在黄瓜中，性别分化主要由遗传物质控制，但植物生长调节剂也可以影响甚至改变它。然而，施用外源生长素对黄瓜性别分化的影响大多局限于生理水平。本研究探讨了不同外源生长素浓度对不同突变性控制基因型品种的影响，发现外源吲哚-3-乙酸（IAA）对黄瓜雌性增强存在剂量效应。一些 ACC 合成酶 (ACS) 家族成员可以直接对外源 IAA 的诱导作出反应，以改善内源乙烯合成，并且该过程可以独立于先前鉴定的与性别相关的 ACC 氧化酶 CsACO2。我们进一步证明，芽再生增强剂2（ESR2）响应外源生长素的诱导，可以通过结合启动子中的ERE顺式作用元件区域直接激活CsACS2表达，然后增加内源乙烯含量，从而可能诱导雌性。这些发现表明，外源生长素通过诱导性别控制基因和促进乙烯合成来改善黄瓜雌性。