Sex- and Gamete-Specific Patterns of X Chromosome Segregation in a Trioecious Nematode.
Sex- and Gamete-Specific Patterns of X Chromosome Segregation in a Trioecious Nematode.
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X染色体隔离的性别和配子特异性模式。
DOI：
10.1016/j.cub.2017.11.037
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发表时间：
2018-01-08
期刊：
影响因子：
--
通讯作者：
Pires-daSilva A
中科院分区：
文献类型：
--
作者：
Tandonnet S;Farrell MC;Koutsovoulos GD;Blaxter ML;Parihar M;Sadler PL;Shakes DC;Pires-daSilva A
减数分裂中的三个关键步骤允许二倍体生物产生单倍体配子：（1）同源染色体（同源物）配对并进行交换;（2）同源物分离到相反的两极;（3）姐妹染色单体分离到相反的两极。在许多线虫中发现的XX/XO性别决定系统有利于减数分裂的研究，因为变异很容易识别。在这里，我们表明，减数分裂分离的X染色体在雌雄异株的线虫Auanema rhodensis根据性别（雌雄同体，女性，或男性）和配子发生（卵子发生或精子发生）的类型。在这个物种中，XO雄性只产生带有X的精子。未配对的X染色体早熟地分离成姐妹染色单体，姐妹染色单体与常染色体组共分离以产生功能性单倍X精子。另一组常染色体被丢弃到残留体内。在这里，我们探讨X染色体的行为在女性和两性减数分裂。X染色体在XX雌性卵子发生过程中按照典型模式分离，产生单倍X卵母细胞，而在XX两性卵子发生过程中，它们分离到第一极体，产生空X卵母细胞。因此，XX雌雄同体和雄性之间的杂交只产生雄性后代。在两性精子发生过程中，X染色体的姐妹染色单体在减数分裂I期间分离，同源X染色单体分离到功能精子中以产生双倍X精子。考虑到减数分裂程序中的这些种内、个体内和配子发生内的变化，A. rhodensis是研究减数分裂可塑性及其如何调节的理想模型。根据正常的孟德尔遗传学，XX雌性产生单倍-X卵母细胞在杂交后代中，儿子总是从父亲Tandonnet等人那里继承X染色体。结果表明，在三性线虫A. rhodensis中，X染色体在性别和配子发生类型之间存在不同的分离：雌雄同体产生双倍X精子和nullo-X卵母细胞，而雌性产生单倍X卵母细胞。此外，它有一种独特的X染色体遗传形式，从父亲到儿子。
Three key steps in meiosis allow diploid organisms to produce haploid gametes: (1) homologous chromosomes (homologs) pair and undergo crossovers; (2) homologs segregate to opposite poles; and (3) sister chromatids segregate to opposite poles. The XX/XO sex determination system found in many nematodes facilitates the study of meiosis because variation is easily recognized. Here we show that meiotic segregation of X chromosomes in the trioecious nematode Auanema rhodensis varies according to sex (hermaphrodite, female, or male) and type of gametogenesis (oogenesis or spermatogenesis). In this species, XO males exclusively produce X-bearing sperm. The unpaired X precociously separates into sister chromatids, which co-segregate with the autosome set to generate a functional haplo-X sperm. The other set of autosomes is discarded into a residual body. Here we explore the X chromosome behavior in female and hermaphrodite meioses. Whereas X chromosomes segregate following the canonical pattern during XX female oogenesis to yield haplo-X oocytes, during XX hermaphrodite oogenesis they segregate to the first polar body to yield nullo-X oocytes. Thus, crosses between XX hermaphrodites and males yield exclusively male progeny. During hermaphrodite spermatogenesis, the sister chromatids of the X chromosomes separate during meiosis I, and homologous X chromatids segregate to the functional sperm to create diplo-X sperm. Given these intra-species, intra-individual, and intra-gametogenesis variations in the meiotic program, A. rhodensis is an ideal model for studying the plasticity of meiosis and how it can be modulated. Crosses between A. rhodensis hermaphrodites and males generate only male progeny Hermaphrodites generate mostly nullo-X oocytes and diplo-X sperm Following normal Mendelian genetics, XX females produce haplo-X oocytes In cross-progeny, sons always inherit the X chromosome from the father Tandonnet et al. show that the X chromosomes segregate differently between sexes and type of gametogenesis in the three-sexed nematode A. rhodensis: hermaphrodites produce diplo-X sperm and nullo-X oocytes, whereas females produce haplo-X oocytes. Furthermore, it has a unique form of X chromosome heritability, from father to son.
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