Adaptive Evolution Involving Gene Duplication and Insertion of a Novel Ty1/copia-Like Retrotransposon in Soybean
Adaptive Evolution Involving Gene Duplication and Insertion of a Novel Ty1/copia-Like Retrotransposon in Soybean
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DOI：
10.1007/s00239-009-9262-1
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发表时间：
2009-08-01
影响因子：
3.9
通讯作者：
Abe, Jun
中科院分区：
文献类型：
--
作者：
Kanazawa, Akira;Liu, Baohui;Abe, Jun
基因复制是产生进化新奇的主要力量，从而导致对环境的适应。我们之前在古多倍体物种大豆中鉴定出了编码光敏色素 A (phyA) 的两个旁系同源物 GmphyA1 和 GmphyA2。 GmphyA2 由负责光周期敏感性的 E4 基因座编码。在光周期不敏感品系中，GmphyA2 通过在外显子 1 中插入逆转录转座子而失活。在这里，我们描述了该元素的详细特征及其从包含该元素的等位基因的分布推断出的进化意义。结构特征表明，该元件（称为 SORE-1）是大豆中一种新型 Ty1/copia 样逆转录转座子，在系统发育上与 Sto-4、BARE-1 和 RIRE1 元件相关。该元件具有转录活性，并且转录受到表观遗传机制的部分抑制。在大豆基因组序列数据库中检测到与SORE-1同源的序列，其中大部分序列表现为沉默。仅在日本北部地区种植的栽培大豆品系中检测到带有 SORE-1 插入的 GmphyA2，这与 GmphyA2 功能障碍引起的光周期不敏感性是允许在高纬度地区种植大豆的遗传变化之一的观点一致。考虑到两个phyA基因所赋予的遗传冗余，我们提出了一个新的基因复制和反转录转座子转座后果的模型：当基因复制时，反转录转座子插入导致基因功能丧失，可以导致适应性进化，而生物体则通过基因复制带来的缓冲效应来维持。
Gene duplication is a major force for generating evolutionary novelties that lead to adaptations to environments. We previously identified two paralogs encoding phytochrome A (phyA), GmphyA1 and GmphyA2, in soybean, a paleopolyploid species. GmphyA2 is encoded by the E4 locus responsible for photoperiod sensitivity. In photoperiod insensitive lines, GmphyA2 is inactivated by the insertion of a retrotransposon in exon 1. Here, we describe the detailed characterization of the element and its evolutionary significance inferred from the distribution of the allele that harbors the element. Structural characteristics indicated that the element, designated SORE-1, is a novel Ty1/copia-like retrotransposon in soybean, which was phylogenetically related to the Sto-4, BARE-1, and RIRE1 elements. The element was transcriptionally active, and the transcription was partially repressed by an epigenetic mechanism. Sequences homologous with SORE-1 were detected in a genome sequence database of soybean, most of which appeared silent. GmphyA2 that harbors the SORE-1 insertion was detected only in cultivated soybean lines grown in northern regions of Japan, consistent with the notion that photoperiod insensitivity caused by the dysfunction of GmphyA2 is one of genetic changes that allowed soybean cultivation at high latitudes. Taking into account that genetic redundancy is conferred by the two phyA genes, we propose a novel model for the consequences of gene duplication and transposition of retrotransposons: when the gene is duplicated, retrotransposon insertion that causes the loss of a gene function can lead to adaptive evolution while the organism is sustained by the buffering effect brought about by gene duplication.