New insights into placozoan sexual reproduction and development.
New insights into placozoan sexual reproduction and development.
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对Placozoan有性繁殖和发展的新见解。
DOI：
10.1371/journal.pone.0019639
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发表时间：
2011
期刊：
影响因子：
3.7
通讯作者：
Schierwater B
中科院分区：
文献类型：
--
作者：
Eitel M;Guidi L;Hadrys H;Balsamo M;Schierwater B
解开动物的生命周期和胚胎发育是理解动物生物学的基础，通常有助于揭示系统发育关系。了解后生动物进化的一个关键类群是早期分枝的扁平动物门，它迅速引起了越来越多的关注。尽管对胎盘动物的研究已有一百多年的历史，但这一神秘门类的生命周期仍然未知。悬铃虫是一种独特的模式系统，其核基因组是在基础生物学(即生命周期和发育)尚未解开之前就公布的。四项有机学研究报告了卵母细胞的发育，一项遗传学研究至少在过去支持了自然种群有性繁殖的假说。在这里，我们报道了关于悬铃虫有性繁殖和胚胎发育的新观察结果，并支持了目前有性繁殖的假说。对卵母细胞和表达的精子标志物的定期观察为胎盘动物在野外有性繁殖提供了支持。利用全基因组和EST序列以及额外的cDNA克隆，我们鉴定了5个保守的精子标记，它们在精子发生的不同阶段具有特征。我们还报告了胚胎发育到128细胞阶段的细节，以及在早期发育过程中出现的新的超微结构特征。这些结果表明，精子和卵母细胞的产生和成熟发生在不同的胎盘动物身上，克隆血统除了标准的营养生殖模式外，还进行双性生殖。观察结果的总和最符合这样一个假设，即一个简单的生命周期，双性生殖和营养生殖之间的生殖模式交替。
Unraveling animal life cycles and embryonic development is basic to understanding animal biology and often sheds light on phylogenetic relationships. A key group for understanding the evolution of the Metazoa is the early branching phylum Placozoa, which has attracted rapidly increasing attention. Despite over a hundred years of placozoan research the life cycle of this enigmatic phylum remains unknown. Placozoa are a unique model system for which the nuclear genome was published before the basic biology (i.e. life cycle and development) has been unraveled. Four organismal studies have reported the development of oocytes and one genetic study has nourished the hypothesis of sexual reproduction in natural populations at least in the past. Here we report new observations on sexual reproduction and embryonic development in the Placozoa and support the hypothesis of current sexual reproduction. The regular observation of oocytes and expressed sperm markers provide support that placozoans reproduce sexually in the field. Using whole genome and EST sequences and additional cDNA cloning we identified five conserved sperm markers, characteristic for different stages in spermatogenesis. We also report details on the embryonic development up to a 128-cell stage and new ultrastructural features occurring during early development. These results suggest that sperm and oocyte generation and maturation occur in different placozoans and that clonal lineages reproduce bisexually in addition to the standard mode of vegetative reproduction. The sum of observations is best congruent with the hypothesis of a simple life cycle with an alternation of reproductive modes between bisexual and vegetative reproduction.
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影响因子：
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作者：
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通讯作者：
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