Biology Department, Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950 USA.
Institute for Biodiversity and Sustainability Science, California Academy of Sciences, San Francisco, CA 94118, USA.
Proc Biol Sci. 2023 Jan 25;290(1991):20221766. doi: 10.1098/rspb.2022.1766. Epub 2023 Jan 18.
In many animals, the germline differentiates early in embryogenesis, so only mutations that accumulate in germ cells are inherited by offspring. Exceptions to this developmental process may indicate other mechanisms have evolved to limit the effects of deleterious mutation accumulation. Stony corals are animals that can live for hundreds of years and have been thought to produce gametes from somatic tissue. To clarify conflicting evidence about germline-soma distinction in corals, we sequenced high coverage, full genomes with technical replicates for parent coral branches and their sperm pools. We identified post-embryonic single nucleotide variants (SNVs) unique to each parent branch, then checked if each SNV was shared by the respective sperm pool. Twenty-six per cent of post-embryonic SNVs were shared by the sperm and 74% were not. We also identified germline SNVs, those that were present in the sperm but not in the parent. These data suggest that self-renewing stem cells differentiate into germ and soma throughout the adult life of the colony, with SNV rates and patterns differing markedly in stem, soma and germ lineages. In addition to informing the evolution of germlines in metazoans, these insights inform how corals may generate adaptive diversity necessary in the face of global climate change.
在许多动物中，生殖细胞在胚胎发生早期就分化了，因此只有积累在生殖细胞中的突变才会遗传给后代。这种发育过程的例外可能表明已经进化出其他机制来限制有害突变积累的影响。石珊瑚是一种可以存活数百年的动物，人们曾认为它们可以从体细胞产生配子。为了澄清关于珊瑚中生殖细胞-体细胞区分的相互矛盾的证据，我们对父母珊瑚枝及其精子库进行了技术重复的高覆盖率全基因组测序。我们确定了每个父母分支特有的胚胎后单核苷酸变异（SNV），然后检查每个 SNV 是否被各自的精子库共享。26%的胚胎后 SNV 与精子共享，74%的 SNV 不共享。我们还鉴定了生殖细胞 SNV，即存在于精子中但不存在于亲本中的 SNV。这些数据表明，自我更新的干细胞在殖民地的整个成年期分化为生殖细胞和体细胞，SNV 率和模式在干细胞、体细胞和生殖系中差异显著。除了为后生动物生殖细胞的进化提供信息外，这些发现还说明了珊瑚如何在面对全球气候变化时产生必要的适应性多样性。
