Origin and Diversification Dynamics of Self-Incompatibility Haplotypes
Origin and Diversification Dynamics of Self-Incompatibility Haplotypes
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DOI：
10.1534/genetics.111.127399
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发表时间：
2011-07-01
期刊：
影响因子：
3.3
通讯作者：
Billiard, Sylvain
中科院分区：
文献类型：
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作者：
Gervais, Camille E.;Castric, Vincent;Billiard, Sylvain
自交不亲和性（Self-incompatibility，SI）是存在于某些两性花植物中的一种遗传系统。在两个连锁基因上表达同源特异性的雌蕊对花粉的识别导致对自体花粉和近亲花粉的排斥，即，避免自交和自交交配，从而增加异交。这些基因通常有许多等位基因，但允许新等位基因进化的条件仍然是个谜。进化的变化在两个基因中显然是必要的，因为任何只影响其中一个基因的突变都会导致一个无功能的自交不亲和单倍型。在这里，我们研究S位点的多样化（即，群体中SI单倍型总数的稳定增加，通过引入新的SI单倍型），既可以确定性地（通过分析研究无限群体中突变的命运），也可以模拟有限群体。我们表明，允许多样化的条件是严格得多的花粉和雌蕊基因的经常性突变的有限人口，这表明多样化是可能的，在一个panmic人口。我们发现，新的SI单倍型出现最快的人群中，SI单倍型很少，我们讨论了一些影响的经验数据的S-等位基因。然而，在我们的模拟中的等位基因数从来没有达到的值，如在植物中观察到的SI系统已被研究，我们建议扩展我们的模型，可以调和的理论和数据。
Self-incompatibility (SI) is a genetic system found in some hermaphrodite plants. Recognition of pollen by pistils expressing cognate specificities at two linked genes leads to rejection of self pollen and pollen from close relatives, i.e., to avoidance of self-fertilization and inbred matings, and thus increased outcrossing. These genes generally have many alleles, yet the conditions allowing the evolution of new alleles remain mysterious. Evolutionary changes are clearly necessary in both genes, since any mutation affecting only one of them would result in a nonfunctional self-compatible haplotype. Here, we study diversification at the S-locus (i.e., a stable increase in the total number of SI haplotypes in the population, through the incorporation of new SI haplotypes), both deterministically (by investigating analytically the fate of mutations in an infinite population) and by simulations of finite populations. We show that the conditions allowing diversification are far less stringent in finite populations with recurrent mutations of the pollen and pistil genes, suggesting that diversification is possible in a panmictic population. We find that new SI haplotypes emerge fastest in populations with few SI haplotypes, and we discuss some implications for empirical data on S-alleles. However, allele numbers in our simulations never reach values as high as observed in plants whose SI systems have been studied, and we suggest extensions of our models that may reconcile the theory and data.