Abstract：
Self-incompatibility plays a vital role in angiosperms, by preventing inbreeding depression and maintaining genetic diversity within populations. Following polyploidization, many angiosperm species transition from self-incompatibility to self-compatibility. Here, we investigated the S-locus in Brassicaceae and identified distinct origins for the sRNA loci, SMI and SMI2 (SCR Methylation Inducer 1 and 2), within the S-locus. The SMI loci were found to be widespread in Cruciferae, whereas the SMI2 loci were exclusive to Brassica species. Additionally, we discovered four major S-haplotypes (BnS-1, BnS-6, BnS-7, and BnS-1300) in rapeseed. Overexpression of BnSMI-1 in self-incompatible Brassica napus (\'S-70S1300S6 \') resulted in a significant increase in DNA methylation in the promoter regions of BnSCR-6 and BnSCR-1300, leading to self-compatibility. Conversely, by overexpressing a point mutation of BnSmi-1 in the \'S-70S1300S6 \' line, we observed lower levels of DNA methylation in BnSCR-6 and BnSCR-1300 promoters. Furthermore, the overexpression of BnSMI2-1300 in the \'SI-326S7S6 \' line inhibited the expression of BnSCR-7 through transcriptional repression of the Smi2 sRNA from the BnS-1300 haplotype. Our study demonstrates that the self-compatibility of rapeseed is determined by S-locus sRNA-mediated silencing of SCR after polyploidization, which helps to further breed self-incompatible or self-compatible rapeseed lines, thereby facilitating the utilization of heterosis.
摘要：
自交不亲和在被子植物中起着至关重要的作用,通过防止近亲繁殖抑郁症和维持种群内的遗传多样性。多倍体化之后,许多被子植物物种从自交不亲和过渡到自亲和。这里,我们调查了十字花科的S基因座，并确定了sRNA基因座的不同来源，SMI和SMI2（SCR甲基化诱导物1和2），在S基因座内。发现SMI基因座广泛存在于十字花科，而SMI2基因座是芸苔属物种所独有的。此外,我们在油菜籽中发现了四种主要的S单倍型（BnS-1，BnS-6，BnS-7和BnS-1300）。BnSMI-1在自交不亲和的甘蓝型油菜（\'S-70S1300S6\'）中的过表达导致BnSCR-6和BnSCR-1300启动子区域的DNA甲基化显着增加，从而导致自交性。相反，通过在\'S-70S1300S6\'系中过表达BnSmi-1的点突变，我们在BnSCR-6和BnSCR-1300启动子中观察到较低水平的DNA甲基化。此外，\'SI-326S7S6\'细胞系中BnSMI2-1300的过表达通过转录抑制来自BnS-1300单倍型的Smi2sRNA来抑制BnSCR-7的表达。我们的研究表明，油菜籽的自相容性是由S-基因座sRNA介导的SCR沉默后多倍体化，这有助于进一步繁殖自交或自交的油菜籽系，从而促进杂种优势的利用。
