Abstract：
Complete disruption of critical genes is generally accompanied by severe growth and developmental defects, which dramatically hinder its utilization in crop breeding. Identifying subtle changes, such as single nucleotide polymorphisms (SNPs), in critical genes that specifically modulate a favorable trait is a prerequisite to fulfill breeding potential. Here, we found two SNPs in the E-class floral organ identity gene cucumber (Cucumis sativus) SEPALLATA2 (CsSEP2) that specifically regulate fruit length. Haplotype (HAP) 1 (8G2667A) and HAP2 (8G2667T) exist in natural populations, whereas HAP3 (8A2667T) is induced by ethyl methanesulfonate mutagenesis. Phenotypic characterization of four near-isogenic lines and a mutant line showed that HAP2 fruits are significantly longer than those of HAP1, and those of HAP3 are 37.8% longer than HAP2 fruit. The increasing fruit length in HAP1-3 was caused by a decreasing inhibitory effect on CRABS CLAW (CsCRC) transcription (a reported positive regulator of fruit length), resultinged in enhanced cell expansion. Moreover, a 7638G/A-SNP in melon (Cucumis melo) CmSEP2 modulates fruit length in a natural melon population via the conserved SEP2-CRC module. Our findings provide a strategy for utilizing essential regulators with pleiotropic effects during crop breeding.
摘要：
关键基因的完全破坏通常伴随着严重的生长和发育缺陷，这极大地阻碍了其在作物育种中的利用。识别微妙的变化，例如单核苷酸多态性（SNP），在关键基因中特异性调节有利性状是实现育种潜力的先决条件。这里,我们在E类花器官身份基因黄瓜（Cucumissativus）SEPALLATA2（CsSEP2）中发现了两个SNP，它们特异性调节果实长度。单倍型(HAP)1(8G2667A)和HAP2(8G2667T)存在于自然种群中,而HAP3(8A2667T)是由甲磺酸乙酯诱变诱导的。四个近等基因系和一个突变系的表型表征表明，HAP2果实明显长于HAP1，HAP3果实比HAP2果实长37.8%。HAP1-3果实长度的增加是由对CRABSCLAW（CsCRC）转录（据报道果实长度的正调节因子）的抑制作用降低引起的。导致细胞扩增增强。此外，甜瓜（Cucumismelo）中的7638G/A-SNPCmSEP2通过保守的SEP2-CRC模块调节天然甜瓜种群中的果实长度。我们的发现为在作物育种过程中利用具有多效性作用的必需调节剂提供了策略。
