Assessing the Extent of Substitution Rate Variation of Retrotransposon Long Terminal Repeat Sequences in Oryza sativa and Oryza glaberrimaReportar como inadecuado

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, Volume 3, Issue 4, pp 242–250

First Online: 31 July 2010Received: 26 February 2010Accepted: 08 July 2010


Long Terminal Repeat retrotransposons LTR-RTs are a major component of several plant genomes. Important insights into the evolutionary dynamics of these elements in a genome are provided by the comparative study of their insertion times. These can be inferred by the comparison of pairs of LTRs flanking intact LTR-RTs in combination with an estimated substitution rate. Over the past several years, different substitution rates have been proposed for LTRs in crop plants. However, very little is known about the extent of substitution rate variation and the factors contributing to this variation, so the rates currently used are generally considered rough estimators of actual rates. To evaluate the extent of substitution rate variation in LTRs, we identified 70 orthologous LTRs on the short arms of chromosome 3 of both Oryza sativa and Oryza glaberrima, species that diverged ∼0.64 Ma. Since these orthologous sequences were present in a common ancestor prior to species divergence, nucleotide differences identified in comparing these regions must correspond to mutations accumulated post-speciation, thereby giving us the opportunity to study LTR substitution rate variation in different elements across these short arms. As a control, we analyzed a similar amount of non-repeat-related sequences collected near the orthologous LTRs. Our analysis showed that substitution rate variation in LTRs is greater than 5-fold, is positively correlated with G+C content, and tends to increase near centromeric regions. We confirmed that in the vast majority of cases, LTRs mutate faster than their corresponding non-repeat-related neighboring sequences.

KeywordsSubstitution rate Long terminal repeat Retrotransposon Electronic supplementary materialThe online version of this article doi:10.1007-s12284-010-9046-7 contains supplementary material, which is available to authorized users.

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Autor: Andrea Zuccolo - Aswathy Sebastian - Yeisoo Yu - Scott Jackson - Steve Rounsley - Dean Billheimer - Rod A. Wing


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