Meiosis Gene Inventory of Four Ciliates Reveals the Prevalence of a Synaptonemal Complex-Independent Crossover Pathway
Meiosis Gene Inventory of Four Ciliates Reveals the Prevalence of a Synaptonemal Complex-Independent Crossover Pathway
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DOI：
10.1093/molbev/mst258
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发表时间：
2014-03-01
影响因子：
10.7
通讯作者：
Dunthorn, Micah
中科院分区：
文献类型：
--
作者：
Chi, Jingyun;Mahe, Frederic;Dunthorn, Micah
为了确定哪些减数分裂基因存在于纤毛虫中，并寻找它们可能通过哪些重组途径的线索，对11个减数分裂特异性基因和40个减数分裂相关基因的4个基因组进行了编目。我们发现，四膜虫嗜热，草履虫tetraurelia，小瓜虫multifiliis，和Oxytricha trifallax共享的减数分裂基因组是一致的Mus81依赖的II类交叉途径，被认为是在大多数模型真核生物中的次要流行。很少有证据表明，一个典型的I类交叉途径，需要形成一个联会复合体（SC）。这一基因清单表明，在纤毛虫减数分裂过程在很大程度上依赖于有丝分裂修复蛋白执行减数分裂重组。我们建议，类I的交叉和SC减少纤毛虫的进化过程中的某个时候。与这种减少相一致，我们提供了显微镜下的证据，只存在退化SC的棘尾虫。此外，一些减数分裂基因的同义突变率较低，这表明，与迄今为止分析的大多数其他核基因相反，纤毛虫减数分裂基因的进化速度比真菌和动物中的基因要慢。
To establish which meiosis genes are present in ciliates, and to look for clues as to which recombination pathways may be treaded by them, four genomes were inventoried for 11 meiosis-specific and 40 meiosis-related genes. We found that the set of meiosis genes shared by Tetrahymena thermophila, Paramecium tetraurelia, Ichthyophthirius multifiliis, and Oxytricha trifallax is consistent with the prevalence of a Mus81-dependent class II crossover pathway that is considered secondary in most model eukaryotes. There is little evidence for a canonical class I crossover pathway that requires the formation of a synaptonemal complex (SC). This gene inventory suggests that meiotic processes in ciliates largely depend on mitotic repair proteins for executing meiotic recombination. We propose that class I crossovers and SCs were reduced sometime during the evolution of ciliates. Consistent with this reduction, we provide microscopic evidence for the presence only of degenerate SCs in Stylonychia mytilus. In addition, lower nonsynonymous to synonymous mutation rates of some of the meiosis genes suggest that, in contrast to most other nuclear genes analyzed so far, meiosis genes in ciliates are largely evolving at a slower rate than those genes in fungi and animals.