Embrapa Recursos Genéticos e Biotecnologia, Brasília, DF, Brazil.
Chromosome Res. 2010 Feb;18(2):227-46. doi: 10.1007/s10577-009-9109-z. Epub 2010 Feb 2.
In this paper, we describe a Ty3-gypsy retrotransposon from allotetraploid peanut (Arachis hypogaea) and its putative diploid ancestors Arachis duranensis (A-genome) and Arachis ipaënsis (B-genome). The consensus sequence is 11,223 bp. The element, named FIDEL (Fairly long Inter-Dispersed Euchromatic LTR retrotransposon), is more frequent in the A- than in the B-genome, with copy numbers of about 3,000 (+/-950, A. duranensis), 820 (+/-480, A. ipaënsis), and 3,900 (+/-1,500, A. hypogaea) per haploid genome. Phylogenetic analysis of reverse transcriptase sequences showed distinct evolution of FIDEL in the ancestor species. Fluorescent in situ hybridization revealed disperse distribution in euchromatin and absence from centromeres, telomeric regions, and the nucleolar organizer region. Using paired sequences from bacterial artificial chromosomes, we showed that elements appear less likely to insert near conserved ancestral genes than near the fast evolving disease resistance gene homologs. Within the Ty3-gypsy elements, FIDEL is most closely related with the Athila/Calypso group of retrovirus-like retrotransposons. Putative transmembrane domains were identified, supporting the presence of a vestigial envelope gene. The results emphasize the importance of FIDEL in the evolution and divergence of different Arachis genomes and also may serve as an example of the role of retrotransposons in the evolution of legume genomes in general.
本文描述了来自异源四倍体花生（Arachis hypogaea）及其可能的二倍体祖先 Arachis duranensis（A 基因组）和 Arachis ipaënsis（B 基因组）的 Ty3-gypsy 反转录转座子。共有序列为 11,223 bp。该元件名为 FIDEL（相当长的分散 euchromatic LTR 反转录转座子），在 A 基因组中比在 B 基因组中更为频繁，其拷贝数约为 3,000（+/-950，A. duranensis）、820（+/-480，A. ipaënsis）和 3,900（+/-1,500，A. hypogaea）每个单倍体基因组。反转录酶序列的系统发育分析表明，FIDEL 在祖先物种中经历了独特的进化。荧光原位杂交显示其在 euchromatin 中的分散分布，而不在着丝粒、端粒区域和核仁组织区域。使用来自细菌人工染色体的配对序列，我们表明元件不太可能插入保守的祖先基因附近，而更可能插入快速进化的抗病基因同源物附近。在 Ty3-gypsy 元件中，FIDEL 与 Athila/Calypso 类逆转录病毒样反转录转座子最为密切相关。鉴定出推定的跨膜结构域，支持存在退化的包膜基因。研究结果强调了 FIDEL 在不同 Arachis 基因组进化和分化中的重要性，也可能成为反转录转座子在豆科基因组进化中作用的一个例子。
