Lucek Kay, Flury Jana M, Willi Yvonne
Department of Environmental Sciences, University of Basel, 4056 Basel, Switzerland.
J Hered. 2025 Jan 3;116(1):43-53. doi: 10.1093/jhered/esae046.
The ability to self-fertilize often varies among closely related hermaphroditic plant species, though, variation can also exist within species. In the North American Arabidopsis lyrata, the shift from self-incompatibility (SI) to selfing established in multiple regions independently, mostly since recent postglacial range expansion. This has made the species an ideal model for the investigation of the genomic basis of the breakdown of SI and its population genetic consequences. By comparing nearby selfing and outcrossing populations across the entire species' geographic distribution, we investigated variation at the self-incompatibility (S-)locus and across the genome. Furthermore, a diallel crossing experiment on one mixed-mating population was performed to gain insight into the inheritance of mating system variation. We confirmed that the breakdown of SI had evolved in several S-locus backgrounds. The diallel suggested the involvement of biparental contributions with dominance relations. Though, the population-level genome-wide association study did not single out clear-cut candidate genes but several regions with one near the S-locus. On the implication side, selfing as compared to outcrossing populations had less than half of the genomic diversity, while the number and length of runs of homozygosity (ROHs) scaled with the degree of inbreeding. Selfing populations with a history of long expansion had the longest ROHs. The results highlight that mating system shift to selfing, its genetic underpinning and the likely negative genomic consequences for evolutionary potential can be strongly interlinked with past range dynamics.
自花受精的能力在亲缘关系相近的雌雄同体植物物种中往往存在差异，不过，种内也可能存在变异。在北美琴叶拟南芥中，从自交不亲和（SI）到自花授粉的转变在多个地区独立发生，主要是自最近一次冰期后的范围扩张以来。这使得该物种成为研究自交不亲和性破坏的基因组基础及其群体遗传后果的理想模型。通过比较整个物种地理分布范围内相邻的自花授粉和异花授粉群体，我们研究了自交不亲和（S-）位点及全基因组的变异。此外，对一个混合交配群体进行了双列杂交实验，以深入了解交配系统变异的遗传情况。我们证实，自交不亲和性的破坏在几个S-位点背景中已经进化。双列杂交表明存在双亲贡献及显性关系。然而，群体水平的全基因组关联研究并未找出明确的候选基因，而是发现了几个区域，其中一个靠近S-位点。在影响方面，与异花授粉群体相比，自花授粉群体的基因组多样性不到一半，而纯合子连续片段（ROHs）的数量和长度与近亲繁殖程度成正比。具有长期扩张历史的自花授粉群体的ROHs最长。研究结果突出表明，交配系统向自花授粉的转变、其遗传基础以及对进化潜力可能产生的负面基因组后果，可能与过去的分布动态密切相关。
