Burgin Grace A, Roda Federico, Farnitano Matthew, Hale Charles, Serrato-Capuchina Antonio, Hopkins Robin
bioRxiv. 2025 May 30:2025.05.27.656016. doi: 10.1101/2025.05.27.656016.
Flowering plants display extensive variation in selfing rate, a trait with significant ecological and evolutionary consequences. Many species use genetic mechanisms to recognize and reject self-pollen (termed self-incompatibility or SI), and the loss of SI is one of the most common evolutionary transitions among flowering plants. Despite the ubiquity of transitions to self-compatibility (SC), little is known about the genetic architecture through which SC evolves. Specifically, it is important to determine if SC has a polygenic or simple genetic basis and if variation in compatibility localizes to the genomic locus causing self-pollen recognition (the " -locus"). (Polemoniaceae) has been a model system for exploring mating system evolution and expresses extensive range-wide variation in the SI response. Here we investigate the genetic architecture of SC variants segregating within this otherwise SI species. Using multiple independent crosses, we uncover numerous QTLs associated with intraspecific variation in SI, consistent with a polygenic genetic architecture. While some QTLs overlap across mapping experiments, other QTLs are unique, suggesting that multiple genetic routes to SC exist. Through these crossing experiments, we demonstrate that has a sporophytic SI system, suggesting that an independent evolution of SI occurred in the lineage containing . We map this novel -locus and find that the genomic region containing the -locus is associated with intraspecific variation in SI in one of the three mapping populations. Although further work is necessary to clarify the conditions under which quantitative variation in SI represents a transitional pathway to complete SC, our study reveals the underlying genetic architecture upon which selection could act to drive this frequent and evolutionarily significant transition.
开花植物在自交率方面表现出广泛的变异，这一性状具有重要的生态和进化意义。许多物种利用遗传机制识别并排斥自花花粉（称为自交不亲和或SI），而SI的丧失是开花植物中最常见的进化转变之一。尽管向自交亲和性（SC）转变的情况普遍存在，但对于SC进化所通过的遗传结构却知之甚少。具体而言，确定SC是具有多基因基础还是简单遗传基础，以及亲和性的变异是否定位于导致自花花粉识别的基因组位点（“S-位点”）非常重要。花荵科植物一直是探索交配系统进化的模型系统，并且在SI反应中表现出广泛的种内变异。在这里，我们研究了在这个原本具有SI的物种中分离的SC变异体的遗传结构。通过多个独立杂交，我们发现了许多与SI种内变异相关的QTL，这与多基因遗传结构一致。虽然一些QTL在不同的定位实验中重叠，但其他QTL是独特的，这表明存在多条通往SC的遗传途径。通过这些杂交实验，我们证明花荵科植物具有孢子体SI系统，这表明在包含花荵科植物的谱系中发生了SI的独立进化。我们对这个新的S-位点进行定位，发现在三个定位群体之一中，包含S-位点的基因组区域与SI的种内变异相关。尽管需要进一步的工作来阐明SI的定量变异在何种条件下代表了向完全SC转变的过渡途径，但我们的研究揭示了潜在的遗传结构，选择可能作用于该结构以推动这种频繁且具有进化意义的转变。
