Shengwei Dou, Tong Zhang, Lulin Wang, Chuang Yang, Chengtao Quan, Xiaomei Liang, Chaozhi Ma, Cheng Dai
New Phytologist, First published:30 November 2023, https://doi.org/10.1111/nph.19451
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.