Selecting one of several mating types through gene segment joining and deletion in Tetrahymena thermophila.
Selecting one of several mating types through gene segment joining and deletion in Tetrahymena thermophila.
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嗜热四膜虫通过基因片段连接和删除选择几种交配类型之一
DOI：
10.1371/journal.pbio.1001518
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发表时间：
2013
期刊：
影响因子：
9.8
通讯作者：
Orias E
中科院分区：
文献类型：
--
作者：
Cervantes MD;Hamilton EP;Xiong J;Lawson MJ;Yuan D;Hadjithomas M;Miao W;Orias E
在四膜虫（Tetrahymena），一种多性别的单细胞生物中，后代的性别是由位点特异性重组事件随机决定的，重组事件组装一个完整的基因对并删除所有其他基因对。单细胞真核生物嗜热四膜虫有七种交配类型。只有当细胞将不同交配类型的细胞识别为非自我时，它们才能交配。作为纤毛虫，四膜虫将生殖细胞和索马分为两个细胞核。在生长过程中，体细胞核负责所有基因的转录，而生殖细胞核保持沉默。在交配过程中，一个新的体细胞核从生殖细胞核中分化出来，交配类型由一个随机过程决定。我们在这里报告，体细胞交配型位点包含一对头对头排列的基因。每个基因编码一个交配型特异性片段和一个跨膜结构域，该结构域为所有交配型所共有。体细胞基因敲除表明，这两个基因是所需的有效的非自我识别和成功的交配，评估对形成和后代生产。生殖系交配型基因座由代表每种潜在交配型的不完整基因对的串联阵列组成。在交配过程中，一个完整的新基因对在体细胞交配型位点组装;一个基因对的不完整基因通过连接到生殖系阵列两端的基因片段而完成。所有其他生殖系基因对在此过程中被删除。这些程序化的DNA重排使其成为一个迷人的交配类型决定系统。 嗜热四膜虫（Tetrahymena thermophila）是一种单细胞生物，有七种性别。两个不同性别的细胞交配后，后代细胞可以是七种性别中的任何一种。在这篇文章中，我们将展示如何做出这种性决定。每个细胞都有两个基因组，每个基因组包含在一个单独的细胞核中。生殖系基因组类似于我们的卵巢或睾丸，包含有性后代的所有遗传信息;体细胞或工作基因组控制细胞的运作（包括其性别）。我们表明，种系基因组包含一个串联阵列，由组织相似但不完整的基因对组成，每种性别各一个。受精后，当一个新的体细胞基因组通过生殖系基因组的一个拷贝的重排产生时，性别被选择。当细胞将阵列两端的DNA片段连接到一个不完整基因对的两端时，一个完整的性别基因对被组装起来;这个基因对因此完成并变得完全功能，而其余的性别基因对被切除并丢失。该过程涉及程序化的、位点特异性的基因组重排，并且发生在所选基因对的相对末端的物理独立重排以高可靠性和精确度发生。
In Tetrahymena, a multi-sexed single-celled organism, the sex of the progeny is randomly determined by site-specific recombination events that assemble one complete gene pair and delete all others. The unicellular eukaryote Tetrahymena thermophila has seven mating types. Cells can mate only when they recognize cells of a different mating type as non-self. As a ciliate, Tetrahymena separates its germline and soma into two nuclei. During growth the somatic nucleus is responsible for all gene transcription while the germline nucleus remains silent. During mating, a new somatic nucleus is differentiated from a germline nucleus and mating type is decided by a stochastic process. We report here that the somatic mating type locus contains a pair of genes arranged head-to-head. Each gene encodes a mating type-specific segment and a transmembrane domain that is shared by all mating types. Somatic gene knockouts showed both genes are required for efficient non-self recognition and successful mating, as assessed by pair formation and progeny production. The germline mating type locus consists of a tandem array of incomplete gene pairs representing each potential mating type. During mating, a complete new gene pair is assembled at the somatic mating type locus; the incomplete genes of one gene pair are completed by joining to gene segments at each end of germline array. All other germline gene pairs are deleted in the process. These programmed DNA rearrangements make this a fascinating system of mating type determination. Tetrahymena thermophila is a single-celled organism with seven sexes. After two cells of different sexes mate, the progeny cells can be of any one of the seven sexes. In this article we show how this sex decision is made. Every cell has two genomes, each contained within a separate nucleus. The germline genome is analogous to that in our ovaries or testes, containing all the genetic information for the sexual progeny; the somatic or working genome controls the operation of the cell (including its sex). We show that the germline genome contains a tandem array of similarly organized but incomplete gene pairs, one for each sex. Sex is chosen after fertilization when a new somatic genome is generated by rearrangement of a copy of the germline genome. One complete sex gene pair is assembled when the cell joins DNA segments at opposite ends of the array to each end of one incomplete gene pair; this gene pair is thus completed and becomes fully functional, while the remaining sex gene pairs are excised and lost. The process involves programmed, site-specific genome rearrangements, and the physically independent rearrangements that occur at opposite ends of the selected gene pair happen with high reliability and precision.
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