Short interspersed nuclear elements (SINEs) are small, non‐autonomous and heterogeneous retrotransposons that are widespread in plants. To explore the amplification dynamics and evolutionary history of SINE populations in representative deciduous tree species, we analyzed the genomes of the six following Salicaceae species: Populus deltoides , Populus euphratica , Populus tremula , Populus tremuloides , Populus trichocarpa , and Salix purpurea . We identified 11 Salicaceae SINE families (SaliS‐I to SaliS‐XI), comprising 27 077 full‐length copies. Most of these families harbor segmental similarities, providing evidence for SINE emergence by reshuffling or heterodimerization. We observed two SINE groups, differing in phylogenetic distribution pattern, similarity and 3′ end structure. These groups probably emerged during the ‘salicoid duplication’ (~65 million years ago) in the Salix –Populus progenitor and during the separation of the genus Salix (45–65 million years ago), respectively. In contrast to conserved 5′ start motifs across species and SINE families, the 3′ ends are highly variable in sequence and length. This extraordinary 3′‐end variability results from mutations in the poly(A) tail, which were fixed by subsequent amplificational bursts. We show that the dissemination of newly evolved 3′ ends is accomplished by a displacement of older motifs, leading to various 3′‐end subpopulations within the SaliS families.

中文翻译：

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3'末端的发散是杨柳科中短暂穿插的核元素（SINE）进化的驱动力。

短散布的核元素（SINE）是在植物中广泛分布的小型，非自治且异质的逆转座子。为了探索代表性落叶树种中SINE种群的扩增动态和进化历史，我们分析了以下6种杨柳科植物的基因组：毛白杨，胡杨，毛白杨，海杨，毛白杨，毛果杨和紫柳。我们鉴定出11个洋杨科SINE家族（SaliS-I至SaliS-XI），包括27,077个全长副本。这些家族中的大多数具有片段相似性，通过改组或异二聚化提供了SINE出现的证据。我们观察到两个SINE组，系统发育分布模式，相似性和3'末端结构不同。这些团体中的“salicoid复制”（〜65万年前）期间可能出现的柳-胡杨祖和属的分离过程中，柳（45-65百万年前）。与跨物种和SINE家族的保守5'起始基序相反，3'末端的序列和长度高度可变。这种非同寻常的3'-末端变异性是由poly（A）尾部的突变引起的，该突变通过随后的扩增爆发而得以固定。我们表明，新进化的3'末端的传播是通过替换较旧的图案来完成的，从而导致SaliS家族中的各种3'-末端亚群。