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首页> 外文期刊>BMC Genomics >Mobilization of retrotransposons as a cause of chromosomal diversification and rapid speciation: the case for the Antarctic teleost genus Trematomus
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Mobilization of retrotransposons as a cause of chromosomal diversification and rapid speciation: the case for the Antarctic teleost genus Trematomus

机译：反转录转座子的动员是染色体多样化和快速物种形成的原因：南极硬骨鱼属Trematomus的情况

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The importance of transposable elements (TEs) in the genomic remodeling and chromosomal rearrangements that accompany lineage diversification in vertebrates remains the subject of debate. The major impediment to understanding the roles of TEs in genome evolution is the lack of comparative and integrative analyses on complete taxonomic groups. To help overcome this problem, we have focused on the Antarctic teleost genus Trematomus (Notothenioidei: Nototheniidae), as they experienced rapid speciation accompanied by dramatic chromosomal diversity. Here we apply a multi-strategy approach to determine the role of large-scale TE mobilization in chromosomal diversification within Trematomus species. Despite the extensive chromosomal rearrangements observed in Trematomus species, our measurements revealed strong interspecific genome size conservation. After identifying the DIRS1, Gypsy and Copia retrotransposon superfamilies in genomes of 13 nototheniid species, we evaluated their diversity, abundance (copy numbers) and chromosomal distribution. Four families of DIRS1, nine of Gypsy, and two of Copia were highly conserved in these genomes; DIRS1 being the most represented within Trematomus genomes. Fluorescence in situ hybridization mapping showed preferential accumulation of DIRS1 in centromeric and pericentromeric regions, both in Trematomus and other nototheniid species, but not in outgroups: species of the Sub-Antarctic notothenioid families Bovichtidae and Eleginopsidae, and the non-notothenioid family Percidae. In contrast to the outgroups, High-Antarctic notothenioid species, including the genus Trematomus, were subjected to strong environmental stresses involving repeated bouts of warming above the freezing point of seawater and cooling to sub-zero temperatures on the Antarctic continental shelf during the past 40 millions of years (My). As a consequence of these repetitive environmental changes, including thermal shocks; a breakdown of epigenetic regulation that normally represses TE activity may have led to sequential waves of TE activation within their genomes. The predominance of DIRS1 in Trematomus species, their transposition mechanism, and their strategic location in “hot spots” of insertion on chromosomes are likely to have facilitated nonhomologous recombination, thereby increasing genomic rearrangements. The resulting centric and tandem fusions and fissions would favor the rapid lineage diversification, characteristic of the nototheniid adaptive radiation.
机译：转座因子（TEs）在脊椎动物谱系多样化伴随的基因组重塑和染色体重排中的重要性仍然是争论的话题。理解TEs在基因组进化中的作用的主要障碍是缺乏对完整分类学组别的比较和综合分析。为了帮助克服这个问题，我们集中研究了南极硬骨目Trumatomus（Notothenioidei：Nototheniidae），因为他们经历了快速的物种形成并伴随着巨大的染色体多样性。在这里，我们采用了一种多策略方法来确定大型TE动员在Trematomus物种内的染色体多样化中的作用。尽管在Trematomus物种中观察到广泛的染色体重排，但我们的测量结果显示出强大的种间基因组大小保守性。在确定13个非猪齿亚目物种的基因组中的DIRS1，吉普赛人和Copia逆转录转座子超家族后，我们评估了它们的多样性，丰度（拷贝数）和染色体分布。在这些基因组中，四个DIRS1家族，九个吉普赛人和两个Copia高度保守。 DIRS1是颤抖基因组中最有代表性的。荧光原位杂交作图表明，DIRS1在着丝粒和其他拟南芥物种的着丝粒和着丝粒区域中优先积累，但没有在外群中：南极亚种类胡萝卜素科Bovichtidae和Eleginopsidae的物种，以及非非类胡萝oid科Percidae的物种。与外部群体相反，包括南北半球类在内的南极高类胡萝卜素物种在过去40年来承受着强烈的环境压力，包括反复回暖到海水冰点以上并冷却到南极大陆架以下的零度以下温度。百万年（我）。这些反复的环境变化的结果，包括热冲击;通常抑制TE活性的表观遗传调控的破坏可能导致其基因组内TE激活的连续波。 DIRS1在Trematomus物种中占主导地位，其转座机制以及它们在染色体插入“热点”中的战略位置可能促进了非同源重组，从而增加了基因组重排。由此产生的中心和串联融合和裂变将有利于快速的谱系多样化，这是非球面适应性辐射的特征。

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