Hotspots of Independent and Multiple Rounds of LTR-retrotransposon Bursts in Brassica Species

• 来源期刊: 园艺学报（英文版）
• 关键词: Brassica LTR-retrotransposon insertion time Raphanus sativus
• 年，卷（期）: 2018,（4）
• 页码范围: 165-174
• 页数: 10页
• 语种: 中文

摘要

Long terminal repeat retrotransposons (LTR-RTs) are a predominant group of plant transposable elements (TEs) that are an important component of plant genomes.A large number of LTR-RTs have been annotated in the genomes of the agronomically important oil and vegetable crops of the genus Brassica.Herein,full-length LTR-RTs in the genomes of Brassica and other closely related species were systematically analyzed.The full-length LTR-RT content varied greatly (from 0.43％ to 23.4％) between different species,with Gypsy-like LTR-RTs constituting a primary group across these genomes.More importantly,many annotated LTR-RTs (from 10.03％ to 33.25％ of all detected LTR-RTs) were found to be enriched in localized hotspot regions.Furthermore,all of the analyzed species showed evidence of having experienced at least one round of a LTR-RT burst,with Raphanus sativus experiencing three or more.Moreover,these relatively ancient LTR-RT amplifications exhibited a clear expansion at specific time points.To gain a further understanding of this timing,Brassica rapa,B.oleracea,and R.sativus were examined for the presence of syntenic regions,but none were present.These findings indicate that these LTR-RT burst events were not inherited from a common ancestor,but instead were species-specific bursts that occurred after the divergence of Brassica species.This study further exemplifies the complexities of TE amplifications during the evolution of plant genomes and suggests that these LTR-RT bursts play an important role in genome expansion and divergence in Brassica species.