Barrière Antoine, Félix Marie-Anne
Institut Jacques Monod, Centre National de la Recherche Scientifique, Universities Paris 6 and 7, Paris, France.
Curr Biol. 2005 Jul 12;15(13):1176-84. doi: 10.1016/j.cub.2005.06.022.
Caenorhabditis elegans is a major model system in biology, yet very little is known about its biology outside the laboratory. In particular, its unusual mode of reproduction with self-fertile hermaphrodites and facultative males raises the question of its frequency of outcrossing in natural populations.
We describe the first analysis of C. elegans individuals sampled directly from natural populations. C. elegans is found predominantly in the dauer stage and with a very low frequency of males versus hermaphrodites. Whereas C. elegans was previously shown to display a low worldwide genetic diversity, we find by comparison a surprisingly high local genetic diversity of C. elegans populations; this local diversity is contributed in great part by immigration of new alleles rather than by mutation. Our results on heterozygote frequency, male frequency, and linkage disequilibrium furthermore show that selfing is the predominant mode of reproduction in C. elegans natural populations but that infrequent outcrossing events occur, at a rate of approximately 1%.
Our results give a first insight in the biology of C. elegans in the natural populations. They demonstrate that local populations of C. elegans are genetically diverse and that a low frequency of outcrossing allows for the recombination of these locally diverse genotypes.
秀丽隐杆线虫是生物学中的主要模式生物，但对于其在实验室之外的生物学特性却知之甚少。特别是，其具有自交能育的雌雄同体和兼性雄虫这种不同寻常的繁殖方式，引发了自然种群中异交频率的问题。
我们描述了对直接从自然种群中采样的秀丽隐杆线虫个体的首次分析。秀丽隐杆线虫主要以 dauer 幼虫阶段被发现，雄虫与雌雄同体的频率非常低。虽然之前的研究表明秀丽隐杆线虫在全球范围内的遗传多样性较低，但通过比较我们发现其种群的局部遗传多样性惊人地高；这种局部多样性在很大程度上是由新等位基因的迁入而非突变造成的。我们关于杂合子频率、雄虫频率和连锁不平衡的结果进一步表明，自交是秀丽隐杆线虫自然种群中的主要繁殖方式，但偶尔会发生异交事件，发生率约为 1%。
我们的结果首次揭示了秀丽隐杆线虫在自然种群中的生物学特性。它们表明秀丽隐杆线虫的局部种群在遗传上是多样的，并且低频率的异交允许这些局部多样的基因型进行重组。
