Sustained heterozygosity across a self-incompatibility locus in an inbred ascidian..
Sustained heterozygosity across a self-incompatibility locus in an inbred ascidian..
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近交海鞘中自交不亲和基因座的持续杂合性。
DOI：
10.1093/molbev/msu268
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发表时间：
2015
影响因子：
10.7
通讯作者：
Satoh N.
中科院分区：
文献类型：
--
作者：
Satou Y;Hirayama K;Mita K;Fujie M;Chiba S;Yoshida R;Endo T;Sasakura Y;Inaba K;Satoh N.
由于自交不亲和基因座保持杂合并且自交不亲和基因座内的重组将是不利的，因此认为自交不亲和基因座有助于染色体的结构和功能分化。虽然雌雄同体的脊索动物，玻璃海鞘，有两个自交不亲和基因，这种不亲和系统是不完整的和自交受精发生在实验室条件下。在这里，我们建立了一个近交系的C。反复自花受精。对该品系的同胞动物的基因组序列进行解码，在7号染色体上发现了一个2.4 Mb的杂合区域。一个自交不亲和基因，Themis-B，在该区域内编码。这一观察结果表明，这个自交不亲和位点及其侧翼区的连锁不平衡有助于形成2.4 Mb杂合区，可能通过重组抑制。我们发现，自然种群中的不同个体具有不同数量和不同组合的Themis-B变异体，并且这些动物的自花受精率不同。我们的研究结果解释了为什么在实验室条件下发生自花受精。这也支持了Themis-Blocus在近交系中优先保持杂合的概念，并有助于2.4-Mb杂合区域的形成。高度的结构变异可能抑制重组，这一长杂合区域可能代表染色体结构分化的初步阶段。
Because self-incompatibility loci are maintained heterozygous and recombination within self-incompatibility loci would be disadvantageous, self-incompatibility loci are thought to contribute to structural and functional differentiation of chromosomes. Although the hermaphrodite chordate,Ciona intestinalis, has two self-incompatibility genes, this incompatibility system is incomplete and self-fertilization occurs under laboratory conditions. Here, we established an inbred strain ofC. intestinalisby repeated self-fertilization. Decoding genome sequences of sibling animals of this strain identified a 2.4-Mbheterozygous region on chromosome 7. A self-incompatibility gene,Themis-B, was encoded within this region. This observation implied that this self-incompatibility locus and the linkage disequilibrium of its flanking region contribute to the formation of the 2.4-Mb heterozygous region, probably through recombination suppression. We showed that different individuals in natural populations had different numbers and different combinations ofThemis-Bvariants, and that the rate of self-fertilization varied among these animals. Our result explains why self-fertilization occurs under laboratory conditions. It also supports the concept that theThemis-Blocus is preferentially retained heterozygous in the inbred line and contributes to the formation of the 2.4-Mb heterozygous region. High structural variations might suppress recombination, and this long heterozygous region might represent a preliminary stage of structural differentiation of chromosomes.