Yashiro Toshihisa, Matsuura Kenji
Laboratory of Insect Ecology, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Laboratory of Insect Ecology, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
Proc Natl Acad Sci U S A. 2014 Dec 2;111(48):17212-7. doi: 10.1073/pnas.1412481111. Epub 2014 Nov 17.
Males and females are in conflict over genetic transmission in the evolution of parthenogenesis, because it enhances female reproductive output but deprives the males' genetic contribution. For males, any trait that coerces females into sexual reproduction should increase their fitness. However, in the termite Reticulitermes speratus, queens produce their replacements (neotenic queens) parthenogenetically while using normal sexual reproduction to produce other colony members. Here, we show that termite queens produce parthenogenetic offspring in the presence of kings by closing the micropyles (sperm gates; i.e., openings for sperm entry) of their eggs. Our field survey showed that termite eggs show large variation in numbers of micropyles, with some having none. Microsatellite analysis showed that embryos of micropyleless eggs develop parthenogenetically, whereas those of eggs with micropyles are fertilized and develop sexually. Surveys of eggs among queens of different age groups showed that queens begin to lay micropyleless eggs when they are older and thus, need to produce their replacements parthenogenetically. In addition, we found clear seasonality in new neotenic queen differentiation and micropyleless egg production. This micropyle-dependent parthenogenesis is the first identification, to our knowledge, of the mechanism through which females control egg fertilization over time in diploid animals, implying a novel route of the evolution of parthenogenesis in favor of female interests without interference from males.
在孤雌生殖的进化过程中，雄性和雌性在基因传递方面存在冲突，因为孤雌生殖提高了雌性的繁殖产量，但剥夺了雄性的基因贡献。对于雄性来说，任何迫使雌性进行有性生殖的性状都应该会提高它们的适应性。然而，在白蚁黄胸散白蚁中，蚁后通过关闭其卵子的卵孔（精子门；即精子进入的开口），在有雄蚁存在的情况下进行孤雌生殖来产生它们的替代者（幼态蚁后），同时通过正常的有性生殖来产生其他蚁群成员。在这里，我们表明白蚁蚁后在有雄蚁存在的情况下通过关闭其卵子的卵孔来产生孤雌生殖后代。我们的野外调查表明，白蚁卵的卵孔数量差异很大，有些没有卵孔。微卫星分析表明，没有卵孔的卵的胚胎进行孤雌生殖发育，而有卵孔的卵的胚胎则受精并进行有性发育。对不同年龄组蚁后的卵进行调查表明，蚁后在年龄较大时开始产没有卵孔的卵，因此需要通过孤雌生殖来产生它们的替代者。此外，我们发现新的幼态蚁后分化和没有卵孔的卵的产生存在明显的季节性。据我们所知，这种依赖卵孔的孤雌生殖是首次鉴定出的二倍体动物中雌性随时间控制卵子受精的机制，这意味着孤雌生殖进化的一条新途径有利于雌性利益而不受雄性干扰。
