Significant expansion of Vicia pannonica genome size mediated by amplification of a single type of giant retroelement
Significant expansion of Vicia pannonica genome size mediated by amplification of a single type of giant retroelement
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DOI：
10.1534/genetics.106.056259
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发表时间：
2006-06-01
期刊：
影响因子：
3.3
通讯作者：
Macas, Jiri
中科院分区：
文献类型：
--
作者：
Neumann, Pavel;Koblizkova, Andrea;Macas, Jiri
分散重复序列的扩增以及最终的消除，尤其是那些源于逆转录转座子的重复序列，是植物基因组之间所观察到的大部分显著大小差异的原因。到目前为止，在大多数已研究的高等植物中，不同家族的元件的差异积累导致了这些差异。在此，我们报道了从豆科植物匈牙利野豌豆（Vicia pannonica）中鉴定出的巨大的Ty3/gypsy样逆转录转座子，它们单独就占该物种基因组的约38%。这些逆转录转座子具有先前在豌豆和苜蓿基因组中鉴定出的Ogre元件的结构特征。这些特征包括极大的尺寸（25kb）、在gag - pol区域上游存在一个额外的开放阅读框，以及一个假定的内含子将prot和rt编码序列分隔开。Ogre元件均匀地分布在匈牙利野豌豆的染色体上，除了含有卫星重复序列的末端区域，它们的单个拷贝显示出极高的序列相似性，并且至少其中一部分具有转录活性，这表明它们是近期扩增的。在其他几个野豌豆属物种中也检测到了类似的元件，但在大多数情况下数量明显较少。然而，Ogre序列的丰度与这些物种的基因组大小之间没有明显的相关性。
Amplification and eventual elimination of dispersed repeats, especially those of the retroelement origin, account for most of the profound size variability observed among plant genomes. In most higher plants investigated so far, differential accumulation of various families of elements contributes to these differences. Here we report the identification of giant Ty3/gypsy-like retrotransposons from the legume plant Vicia pannonica, which alone make up similar to 38% of the genome of this species. These retrotransposons have structural features of the Ogre elements previously identified in the genomes of pea and Medicago. These features include extreme size (25 kb), the presence of an extra ORF upstream of the gag-pol region, and a putative intron dividing the prot and rt coding sequences. The Ogre elements are evenly dispersed on V pannonica chromosomes except for terminal regions containing satellite repeats, their individual copies show extraordinary sequence similarity, and at least part of them are transcriptionally active, which suggests their recent amplification. Similar elements were also detected in several other Vicia species but in most cases in significantly lower numbers. However, there was no obvious correlation of the abundance of Ogre sequences with the genome size of these species.