New Insights into Nested Long Terminal Repeat Retrotransposons in Brassica Species  

作　　者：Lijuan Wei Meili Xiaoa Zeshan An Bi Ma Annaliese S. Mason Wei Qian Jiana Li Donghui Fu 

机构地区：[1]Chongqing Engineering Research Center for Rapeseed, College of Agronomy and Biotechnology, Southwest University, Chongqing 400716, China [2]School of Agriculture and Food Sciences and centre for Integrative I~egume-Research, The University of Queensland, 1:he Universit'y of Queensland,Brisbane 4072, Australia [3]Key Laboratory of Crop Physiology, Ecology and Genetic Breeding, Ministry of Education, Agronomy College, Jiangxi Agricultural University, Nanchang330045, China

出　　处：《Molecular Plant》2013年第2期470-482,共13页分子植物（英文版）

摘　　要：Long terminal repeat （LTR） retrotransposons, one of the foremost types of transposons, continually change or modify gene function and reorganize the genome through bursts of dramatic proliferation. Many LTR-TEs preferen-tially insert within other LTR-TEs, but the cause and evolutionary significance of these nested LTR-TEs are not well under-stood. In this study, a total of 1.52 Gb of Brassica sequence containing 2020 bacterial artificial chromosomes （BACs） was scanned, and six bacterial artificial chromosome （BAC） clones with extremely nested LTR-TEs （LTR-TEs density： 7.24/kb） were selected for further analysis. The majority of the LTR-TEs in four of the six BACs were found to be derived from the rapid proliferation of retrotransposons originating within the BAC regions, with only a few LTR-TEs originating from the proliferation and insertion of retrotransposons from outside the BAC regions approximately 5-23 Mya. LTR-TEs also pref-erably inserted into TA-rich repeat regions. Gene prediction by Genescan identified 207 genes in the 0.84Mb of total BAC sequences. Only a few genes （3/207） could be matched to the Brassica expressed sequence tag （EST） database, indicating that most genes were inactive after retrotransposon insertion. Five of the six BACs were putatively centromeric. Hence, nested LTR-TEs in centromere regions are rapidly duplicated, repeatedly inserted, and act to suppress activity of genes and to reshuffle the structure of the centromeric sequences. Our results suggest that LTR-TEs burst and proliferate on a local scale to create nested LTR-TE regions, and that these nested LTR-TEs play a role in the formation of centromeres.Long terminal repeat （LTR） retrotransposons, one of the foremost types of transposons, continually change or modify gene function and reorganize the genome through bursts of dramatic proliferation. Many LTR-TEs preferen-tially insert within other LTR-TEs, but the cause and evolutionary significance of these nested LTR-TEs are not well under-stood. In this study, a total of 1.52 Gb of Brassica sequence containing 2020 bacterial artificial chromosomes （BACs） was scanned, and six bacterial artificial chromosome （BAC） clones with extremely nested LTR-TEs （LTR-TEs density： 7.24/kb） were selected for further analysis. The majority of the LTR-TEs in four of the six BACs were found to be derived from the rapid proliferation of retrotransposons originating within the BAC regions, with only a few LTR-TEs originating from the proliferation and insertion of retrotransposons from outside the BAC regions approximately 5-23 Mya. LTR-TEs also pref-erably inserted into TA-rich repeat regions. Gene prediction by Genescan identified 207 genes in the 0.84Mb of total BAC sequences. Only a few genes （3/207） could be matched to the Brassica expressed sequence tag （EST） database, indicating that most genes were inactive after retrotransposon insertion. Five of the six BACs were putatively centromeric. Hence, nested LTR-TEs in centromere regions are rapidly duplicated, repeatedly inserted, and act to suppress activity of genes and to reshuffle the structure of the centromeric sequences. Our results suggest that LTR-TEs burst and proliferate on a local scale to create nested LTR-TE regions, and that these nested LTR-TEs play a role in the formation of centromeres.

关 键 词：LTR retrotransposons BRASSICA CENTROMERE retrotransposon-rich transposon burst. 

分 类 号：Q943[生物学—植物学] S635.03[农业科学—蔬菜学]