Dunthorn Micah, Zufall Rebecca A, Chi Jingyun, Paszkiewicz Konrad, Moore Karen, Mahé Frédéric
Department of Ecology, University of Kaiserslautern, Kaiserslautern, Germany.
Department of Biology and Biochemistry, University of Houston, Houston, TX.
Genome Biol Evol. 2017 Jun 1;9(6):1781-1787. doi: 10.1093/gbe/evx125.
The putatively asexual Colpodean ciliates potentially pose a problem to macro-organismic theories of evolution. They are extremely ancient (although asexuality is thought to hasten extinction), and yet there is one apparently derived sexual species (implying an unlikely regain of a complex trait). If macro-organismic theories of evolution also broadly apply to microbial eukaryotes, though, then most or all of the colpodean ciliates should merely be secretively sexual. Here we show using de novo genome sequencing, that colpodean ciliates have the meiotic genes required for sex and these genes are under functional constraint. Along with these genomic data, we argue that these ciliates are sexual given the cytological observations of both micronuclei and macronuclei within their cells, and the behavioral observations of brief fusions as if the cells were mating. The challenge that colpodean ciliates pose is therefore not to evolutionary theory, but to our ability to induce microbial eukaryotic sex in the laboratory.
被认为是无性的肾形目纤毛虫可能给宏观生物进化理论带来问题。它们极其古老（尽管无性生殖被认为会加速灭绝），然而却有一种明显衍生出的有性物种（这意味着一种复杂性状不太可能重新获得）。不过，如果宏观生物进化理论也广泛适用于微生物真核生物，那么大多数或所有肾形目纤毛虫应该只是在秘密地进行有性生殖。在这里，我们通过从头基因组测序表明，肾形目纤毛虫拥有有性生殖所需的减数分裂基因，并且这些基因受到功能限制。结合这些基因组数据，鉴于对其细胞内微核和大核的细胞学观察，以及对短暂融合行为的观察（就好像细胞在交配），我们认为这些纤毛虫是有性生殖的。因此，肾形目纤毛虫带来的挑战并非针对进化理论，而是针对我们在实验室中诱导微生物真核生物有性生殖的能力。
