Data from: Genetic mapping and phylogenetic analysis reveal intraspecific variation in sex chromosomes of the Virginian strawberry

With their extraordinary diversity in sexual systems, flowering plants offer unparalleled opportunities to understand sex determination and to reveal generalities in the evolution of sex chromosomes. Comparative genetic mapping of related taxa with good phylogenetic resolution can delineate the extent of sex chromosome diversity within plant groups, and lead the way to understanding the evolutionary drivers of such diversity. The North American octoploid wild strawberries provide such an opportunity. We performed linkage mapping using targeted sequence capture for the subdioecious western Fragaria virginiana ssp. platypetala and compared the location of its sex-determining region (SDR) to those of two other (sub)dioecious species, the eastern subspecies, F. virginiana ssp. virginiana (whose SDR is at 0–5.5 Mb on chromosome VI of the B2 subgenome), and the sister species F. chiloensis (whose SDR is at 37 Mb on chromosome VI of the Av subgenome). Male sterility was dominant in F. virginiana ssp. platypetala and mapped to a chromosome also in homeologous group VI. Likewise, one major QTL for female fertility overlapped the male sterility region. However, the SDR mapped to a yet another subgenome (B1), and to a different location (13 Mb), but similar to the location inferred in one population of the naturally occurring hybrid between F. chiloensis and F. virginiana (F. x ananassa ssp. cuneifolia). Phylogenetic analysis of chromosomes across the octoploid taxa showed consistent subgenomic composition reflecting shared evolutionary history but also reinforced within-species variation in the SDR-carrying chromosome, suggesting either repeated evolution, or recent turnovers in SDR.开花植物凭借其性别系统的极端多样性，为探究性别决定机制、揭示性染色体演化的普遍规律提供了无与伦比的研究契机。对具有良好系统发育分辨率的近缘类群开展比较遗传作图，能够阐明植物类群内性染色体多样性的范围，并为理解这类多样性的演化驱动因素指明方向。北美八倍体野生草莓便提供了这样的研究机会。本研究针对亚雌雄异株的西部弗吉尼亚草莓宽瓣亚种（Fragaria virginiana ssp. platypetala）开展靶向序列捕获连锁作图，并将其性别决定区域（sex-determining region, SDR）的定位结果与另外两种（亚）雌雄异株物种进行对比：其一为东部亚种弗吉尼亚草莓指名亚种（F. virginiana ssp. virginiana），其SDR定位于B2亚基因组的第6号染色体0–5.5 Mb区间；其二为姐妹种智利草莓（F. chiloensis），其SDR定位于Av亚基因组的第6号染色体37 Mb位置。在弗吉尼亚草莓宽瓣亚种中，雄性不育呈显性性状，且被定位到同属于同祖群VI的染色体上。同样，一个控制雌性育性的主效数量性状位点（QTL）与雄性不育区域存在重叠。不过，该物种的SDR却定位到了另一个亚基因组（B1）的13 Mb位置，这一定位结果与智利草莓和弗吉尼亚草莓的天然杂交种（F. × ananassa ssp. cuneifolia）某自然种群中推测的SDR位置相似。对八倍体类群染色体的系统发育分析显示，其亚基因组组成一致，反映了共同的演化历史，但同时也强化了携带SDR的染色体在种内的变异，这表明性染色体区域要么经历了多次独立演化，要么近期发生了性染色体的更替。