A large portion of animal and plant genomes consists of noncoding DNA. This part includes tandemly repeated sequences and gained attention because it offers exciting insights into genome biology. We investigated satellite-DNA elements of the platyhelminth Schistosoma mansoni, a parasite with remarkable biological features. Schistosoma mansoni lives in the vasculature of humans causing schistosomiasis, a disease of worldwide importance. Schistosomes are the only trematodes that have evolved separate sexes, and the sexual maturation of the female depends on constant pairing with the male. The schistosome karyotype comprises eight chromosome pairs, males are homogametic (ZZ) and females are heterogametic (ZW). Part of the repetitive DNA of S. mansoni are W-elements (WEs), originally discovered as female-specific satellite DNAs in the heterochromatic block of the W-chromosome. Based on new genome and transcriptome data, we performed a reanalysis of the W-element families (WEFs). Besides a new classification of 19 WEFs, we provide first evidence for stage-, sex-, pairing-, gonad-, and strain-specific/preferential transcription of WEs as well as their mobile nature, deduced from autosomal copies of full-length and partial WEs. Structural analyses suggested roles as sources of noncoding RNA-like hammerhead ribozymes, for which we obtained functional evidence. Finally, the variable WEF occurrence in different schistosome species revealed remarkable divergence. From these results, we propose that WEs potentially exert enduring influence on the biology of S. mansoni. Their variable occurrence in different strains, isolates, and species suggests that schistosome WEs may represent genetic factors taking effect on variability and evolution of the family Schistosomatidae.

中文翻译：

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类似卫星的 W 元素：重复、转录和推定的移动遗传因子，对曼氏血吸虫的生物学和进化具有潜在作用

很大一部分动植物基因组由非编码 DNA 组成。这部分包括串联重复的序列，并因为它提供了对基因组生物学的令人兴奋的见解而受到关注。我们研究了扁形虫曼氏血吸虫的卫星 DNA 元素，曼氏血吸虫是一种具有显着生物学特征的寄生虫。曼氏血吸虫生活在人类的脉管系统中，引起血吸虫病，这是一种具有世界重要性的疾病。血吸虫是唯一进化出不同性别的吸虫，雌性的性成熟取决于与雄性的不断配对。血吸虫核型由八对染色体组成，雄性为同配子（ZZ），雌性为异配子（ZW）。S. mansoni 的部分重复 DNA 是 W 元素 (WEs)，最初在 W 染色体的异色块中发现为女性特异性卫星 DNA。基于新的基因组和转录组数据，我们对 W 元素家族 (WEF) 进行了重新分析。除了 19 个 WEF 的新分类外，我们还为 WE 的阶段、性别、配对、性腺和菌株特异性/优先转录以及它们的移动性质提供了第一个证据，从全长和部分WE。结构分析表明作为非编码 RNA 样锤头状核酶来源的作用，我们获得了功能证据。最后，不同血吸虫物种中不同的 WEF 发生率显示出显着的差异。根据这些结果，我们提出 WEs 可能对 S. mansoni 的生物学产生持久的影响。它们在不同菌株中的可变出现，