Evidence for a Common Origin of Homomorphic and Heteromorphic Sex Chromosomes in Distinct Spinacia Species.
Evidence for a Common Origin of Homomorphic and Heteromorphic Sex Chromosomes in Distinct Spinacia Species.
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DOI：
10.1534/g3.115.018671
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发表时间：
2015-06-05
期刊：
影响因子：
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通讯作者：
Onodera Y
中科院分区：
文献类型：
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作者：
Fujito S;Takahata S;Suzuki R;Hoshino Y;Ohmido N;Onodera Y
雌雄异株的Spinacia属被认为包括两个野生近缘种(S. turkestanica Ilj；栽培菠菜（S. oleracea L.）。本研究对21份菠菜种质资源和6个菠菜品种（系）的细胞核和叶绿体序列进行了系统发育分析，以确定3个物种之间的亲缘关系。最大似然序列分析表明，Spinacia植物样品可分为2个单系类群（1组和2组）：1组包括S. oleracea L.和S. turkestanica Ilj的所有材料、品种和系；还有5个中的2个。第二组由剩余的3株紫荆属植物组成。登记入册。通过流式细胞术，我们检测到各组之间核基因组大小的明显差异。组2在花序结构上也表现出两性二态性，这在组1中没有观察到。两组间的种间杂交产生的杂种花粉育性显著降低，并且在第2组中显示雄性为异配子性（XY），在第1组中也是如此。细胞遗传学和DNA标记分析表明，类群1和类群2分别具有同态性染色体对和异型性染色体对（XY），两类群的性染色体对是由共同的祖先性染色体对进化而来。我们的数据表明，Spinacia属可以作为一个很好的模型，用于研究从祖先的同态性染色体对出现异型性染色体对的进化机制。
The dioecious genus Spinacia is thought to include two wild relatives (S. turkestanica Ilj. and S. tetrandra Stev.) of cultivated spinach (S. oleracea L.). In this study, nuclear and chloroplast sequences from 21 accessions of Spinacia germplasm and six spinach cultivars or lines were subjected to phylogenetic analysis to define the relationships among the three species. Maximum-likelihood sequence analysis suggested that the Spinacia plant samples could be classified into two monophyletic groups (Group 1 and Group 2): Group 1 consisted of all accessions, cultivars, and lines of S. oleracea L. and S. turkestanica Ilj. and two of five S. tetrandra Stev. accessions, whereas Group 2 was composed of the three remaining S. tetrandra Stev. accessions. By using flow cytometry, we detected a distinct difference in nuclear genome size between the groups. Group 2 also was characterized by a sexual dimorphism in inflorescence structure, which was not observed in Group 1. Interspecific crosses between the groups produced hybrids with drastically reduced pollen fertility and showed that the male is the heterogametic sex (XY) in Group 2, as is the case in S. oleracea L. (Group 1). Cytogenetic and DNA marker analyses suggested that Group 1 and Group 2 have homomorphic and heteromorphic sex chromosome pairs (XY), respectively, and that the sex chromosome pairs of the two groups evolved from a common ancestral pair. Our data suggest that the Spinacia genus may serve as a good model for investigation of evolutionary mechanisms underlying the emergence of heteromorphic sex chromosome pairs from ancestral homomorphic pairs.