Zervakis Panagiotis-Ioannis, Postel Zoé, Losvik Aleksandra, Fracassetti Marco, Solér Lucile, Proux-Wéra Estelle, Bunikis Ignas, Churcher Allison, Slotte Tanja
Department of Ecology, Environment and Plant Sciences, Science for Life Laboratory, Stockholm University, 106 91, Stockholm, Sweden.
Department of Medical Biochemistry and Microbiology, Uppsala University, National Bioinformatics Infrastructure Sweden (NBIS), Science for Life Laboratory, Uppsala University, 751 23, Uppsala, Sweden.
New Phytol. 2025 Sep;247(6):2964-2981. doi: 10.1111/nph.70392. Epub 2025 Jul 18.
Distyly, an example of convergent evolution, is governed by a supergene, the S-locus, in several species. Recent studies highlight similar genomic architectures of independently evolved S-loci, but its mode of origin and whether similar regulatory pathways underlie the convergent evolution of distyly remains unclear. We examined the evolution of supergenes and mechanisms underlying distyly in Linum species that diverged c. 33 million years ago (Ma). Using haplotype-resolved genomes and population genomics, we identified and characterized the S-loci of Linum perenne (distylous) and Linum grandiflorum (style length dimorphic), and compared them to that of Linum tenue (distylous). We then tested for a conserved hormonal mechanism regulating style length polymorphism in Linum. The S-locus supergene was consistently hemizygous in short-styled individuals across all three species, although it showed variation in size, gene content, repeat elements and extent of recombination suppression. Two S-linked candidate genes, TSS1 (style length) and WDR-44 (anther height/pollen self-incompatibility), were conserved. Consistent with a brassinosteroid-dependent role of TSS1, epibrassinolide treatment revealed a conserved, morph-specific effect on style length. S-locus structural polymorphism, candidate distyly genes and mechanisms regulating style length remain conserved > 30 Ma in Linum. In combination with findings from other systems, our results suggest that the brassinosteroid pathway frequently contributes to style length polymorphism.
花柱异长现象是趋同进化的一个例子，在多个物种中受一个超级基因S位点控制。最近的研究突出了独立进化的S位点具有相似的基因组结构，但其起源方式以及花柱异长现象的趋同进化是否有相似的调控途径仍不清楚。我们研究了约3300万年前分化的亚麻属物种中超级基因的进化以及花柱异长现象背后的机制。利用单倍型解析基因组和群体基因组学，我们鉴定并表征了宿根亚麻（花柱异长）和大花亚麻（花柱长度二态性）的S位点，并将它们与细叶亚麻（花柱异长）的S位点进行比较。然后，我们测试了亚麻中调控花柱长度多态性的保守激素机制。在所有三个物种的短花柱个体中，S位点超级基因始终是半合子，尽管它在大小、基因含量、重复元件和重组抑制程度上存在差异。两个与S位点连锁的候选基因TSS1（花柱长度）和WDR - 44（花药高度/花粉自交不亲和）是保守的。与TSS1依赖油菜素内酯的作用一致，表油菜素内酯处理揭示了对花柱长度的保守的、形态特异性的影响。在亚麻属中，S位点结构多态性、候选花柱异长基因和调控花柱长度的机制在超过3000万年前就一直保持保守。结合其他系统的研究结果，我们的结果表明油菜素内酯途径经常导致花柱长度多态性。
