The dynamic activity of transposable elements (TEs) contributes to the vast diversity of genome size and architecture among plants. Here, we examined the genomic distribution and transposition activity of long terminal repeat retrotransposons (LTR-RTs) in Arabidopsis thaliana (Ath) and three of its relatives, Arabidopsis lyrata (Aly), Eutrema salsugineum (Esa), and Schrenkiella parvula (Spa), in Brassicaceae. Our analyses revealed the distinct evolutionary dynamics of Gypsy retrotransposons, which reflects the different patterns of genome size changes of the four species over the past million years. The rate of Gypsy transposition in Aly is approximately five times more rapid than that of Ath and Esa, suggesting an expanding Aly genome. Gypsy insertions in Esa are strictly confined to pericentromeric heterochromatin and associated with dramatic centromere expansion. In contrast, Gypsy insertions in Spa have been largely suppressed over the last million years, likely as a result of a combination of an inherent molecular mechanism of preferential DNA removal and purifying selection at Gypsy elements. Additionally, species-specific clades of Gypsy elements shaped the distinct genome architectures of Aly and Esa.
转座子的动态活性贡献了植物中基因组大小及架构的巨大差异。该项工作在拟南芥（Ath）及其三个十字花科亲属物种中检查了长末端重复反转位子（long terminal repeat retrotransposons，LTR-RTs）的基因组分布和转座活性。这三个亲属物种为深山拟南芥（Aly）、山嵛菜（Esa）和盐芥（Spa）。该工作的分析揭示了吉普赛（Gypsy）转座子的不同演化动态，反应出这四个物种的基因组大小在过去百万年内变化的不同模式。Aly的Gypsy转座速率比Ath和Eas的大概快5倍，暗示了Aly基因组的扩大。Esa中的Gypsy插入被严格限制在着丝粒周围异染色质并与急剧的着丝粒扩张有关。相比而言，Spa中的Gypsy插入在过去百万年内被大大抑制了，这可能是优选DNA移除这种可遗传分子机制与Gypsy元件负选择共同导致的结果。此外，Gypsy元件的物种特异分支塑造了Aly和Esa不同的基因组架构。该工作的创新之处，是通过对LTR-反转座子的转座活性的分析，特别是针对Gypsy元件超家族的转座活性，可以在短的演化时段内推断植物中基因组大小演化的趋势。





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