In higher plants sexual and asexual reproduction through seeds (apomixis) have evolved as alternative strategies. Evolutionary advantages leading to coexistence of both reproductive modes are currently not well understood. It is expected that accumulation of deleterious mutations leads to a rapid elimination of apomictic lineages from populations. In this line, apomixis originated repeatedly, likely from deregulation of the sexual pathway, leading to alterations in the development of reproductive lineages (germlines) in apomicts as compared to sexual plants. This potentially involves mutations in genes controlling reproduction. Increasing evidence suggests that RNA helicases are crucial regulators of germline development. To gain insights into the evolution of 58 members of this diverse gene family in sexual and apomictic plants, we applied target enrichment combined with Next Generation Sequencing to identify allelic variants from 24 accessions of the genus Boechera, comprising sexual, facultative and obligate apomicts. Interestingly, allelic variants from apomicts did not show consistently increased mutation frequency. Either sequences were highly conserved in any accession, or allelic variants preferentially harbored mutations in evolutionary less conserved C- and N-terminal domains, or presented high mutation load independent of the reproductive mode. Only for a few genes allelic variants harboring deleterious mutations were only identified in apomicts. To test if high sequence conservation correlates with roles in fundamental cellular or developmental processes, we analyzed Arabidopsis thaliana mutant lines in VASA-LIKE (VASL), and identified pleiotropic defects during ovule and reproductive development. This indicates that also in apomicts mechanisms of selection are in place based on gene function.

中文翻译：

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基因功能而不是生殖模式驱动性和无融合生殖的Boechera中RNA解旋酶的进化。

在高等植物中，通过种子（apomixis）的有性和无性繁殖已发展为替代策略。导致两种生殖方式并存的进化优势目前尚不十分清楚。预期有害突变的积累导致种群中无融合生殖谱系的快速消除。在这条线中，无融合生殖反复起源，可能是由于性途径的失控，导致与有性植物相比，无融合生殖生殖系（生殖系）发育的改变。这可能涉及控制繁殖的基因突变。越来越多的证据表明，RNA解旋酶是种系发育的关键调节剂。为了深入了解性和无融合生殖植物中58个成员的进化，我们将靶标富集与下一代测序相结合，从Boechera属的24个种中鉴定等位基因变体，包括性，兼性和专性无融合生殖。有趣的是，来自无融合生殖细胞的等位基因变体并未显示出持续增加的突变频率。任一序列在任何登录物中均高度保守，或者等位基因变体优先在进化上较不保守的C和N端结构域中携带突变，或呈现出与繁殖方式无关的高突变负荷。仅对于少数基因，仅在无融合生殖细胞中鉴定出具有有害突变的等位基因变体。为了测试高序列保守性是否与基本细胞或发育过程中的作用相关，我们分析了VASA-LIKE（VASL）中的拟南芥突变株，并鉴定出胚珠和生殖发育过程中的多效性缺陷。这表明在无融合生殖中，基于基因功能的选择机制也就位。