Gynoecy instability in cucumber (Cucumis sativus L.) is due to unequal crossover at the copy number variation-dependent Femaleness (F) locus
Gynoecy instability in cucumber (Cucumis sativus L.) is due to unequal crossover at the copy number variation-dependent Femaleness (F) locus
复制标题
黄瓜 (Cucumis sativus L.) 的雌花期不稳定性是由于拷贝数变异依赖性雌性 (F) 基因座的不等交叉所致
DOI：
10.1038/s41438-020-0251-2
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发表时间：
2020-03-15
影响因子：
8.7
通讯作者：
Weng, Yiqun
中科院分区：
文献类型：
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作者：
Li, Zheng;Han, Yonghua;Weng, Yiqun
黄瓜（Cucumis sativus）是一种重要的蔬菜作物，杂交黄瓜的雌雄同体对产量的提高起着至关重要的作用。黄瓜具有独特的雌同体性表达遗传系统，这是由基于拷贝数变异（CNV）、显性和剂量依赖性的雌性(F)位点决定的。然而，这种雌核表达系统似乎不稳定，因为在依赖f的雌核黄瓜自交系中经常可以发现雌核植株。我们假设雌核不稳定性（雌核丧失）可能是由于CNV重复单元减数分裂期间不平等交叉（UCO）造成的。在本研究中，我们利用高通量基因组重测序、fiber-FISH和基因组qPCR分析，首次确认并完善了F位点的结构，这是一个30.2 kb串联重复序列的CNV。雌蕊植物含有CsACS1、CsACS1G和CsMYB三个基因，其中CsACS1G是CsACS1的重复基因，但其远端启动子可能与雌蕊性别表达有关。在自花雌交自交系的两个大群体中，发现“雌交丧失”突变具有相似的突变率（~ 0.12%）。我们发现这些突变体失去了CsACS1G。此外，我们在自然种群中发现了携带两个CSACS1G拷贝的雌交系。我们提出了一个模型来解释f依赖性黄瓜的雌核不稳定性，这是由减数分裂期间CSACS1/G单位之间的UCO引起的。这些发现提供了一个令人信服的案例，即经济上重要性状的表型变异与F位点拷贝数的动态变化有关。该研究对黄瓜育种也具有重要意义。
Cucumber, Cucumis sativus is an important vegetable crop, and gynoecy has played a critical role in yield increase of hybrid cucumber production. Cucumber has a unique genetic system for gynoecious sex expression, which is determined by the copy number variation (CNV)-based, dominant, and dosage-dependent femaleness (F) locus. However, this gynoecy expression system seems unstable since monecious plants could often be found in F-dependent gynoecious cucumber inbreds. We hypothesized that gynoecy instability (gynoecy loss) may be due to unequal crossing over (UCO) during meiosis among repeat units of the CNV. In this study, using high throughput genome resequencing, fiber-FISH and genomic qPCR analyses, we first confirmed and refined the structure of the F locus, which was a CNV of a 30.2-kb tandem repeat. Gynoecious plants contained three genes: CsACS1, CsACS1G, and CsMYB, of which CsACS1G is a duplication of CsACS1 but with a recombinant distal promoter that may contribute to gynoecy sex expression. In two large populations from self-pollinated gynoecious inbred lines,‘gynoecy loss’ mutants were identified with similar mutation rates (~ 0.12%). We show that these monecious mutants have lost CsACS1G. In addition, we identified gynoecious lines in natural populations that carry two copies of CSACS1G. We proposed a model to explain gynoecy instability in F-dependent cucumbers, which is caused by UCO among CSACS1/G units during meiosis. The findings present a convincing case that the phenotypic variation of an economically important trait is associated with the dynamic changes of copy numbers at the F locus. This work also has important implications in cucumber breeding.