Manetti M E, Rossi M, Nakabashi M, Grandbastien M A, Van Sluys Marie Anne
GaTE Lab, Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, IBUSP, Rua do Matão, 277, São Paulo, SP, 05508-090, Brazil.
Mol Genet Genomics. 2009 Mar;281(3):261-71. doi: 10.1007/s00438-008-0408-4. Epub 2008 Dec 18.
Eukaryotic genome expansion/retraction caused by LTR-retrotransposon activity is dependent on the expression of full length copies to trigger efficient transposition and recombination-driven events. The Tnt1 family of retrotransposons has served as a model to evaluate the diversity among closely related elements within Solanaceae species and found that members of the family vary mainly in their U3 region of the long terminal repeats (LTRs). Recovery of a full length genomic copy of Retrosol was performed through a PCR-based approach from wild potato, Solanum oplocense. Further characterization focusing on both LTR sequences of the amplified copy allowed estimating an approximate insertion time at 2 million years ago thus supporting the occurrence of transposition cycles after genus divergence. Copy number of Tnt1-like elements in Solanum species were determined through genomic quantitative PCR whereby results sustain that Retrosol in Solanum species is a low copy number retrotransposon (1-4 copies) while Retrolyc1 has an intermediate copy number (38 copies) in S. peruvianum. Comparative analysis of retrotransposon content revealed no correlation between genome size or ploidy level and Retrosol copy number. The tetraploid cultivated potato with a cellular genome size of 1,715 Mbp harbours similar copy number per monoploid genome than other diploid Solanum species (613-884 Mbp). Conversely, S. peruvianum genome (1,125 Mbp) has a higher copy number. These results point towards a lineage specific dynamic flux regarding the history of amplification/activity of Tnt1-like elements in the genome of Solanum species.
由LTR反转录转座子活性引起的真核基因组扩增/收缩依赖于全长拷贝的表达，以触发有效的转座和重组驱动事件。反转录转座子的Tnt1家族已成为评估茄科物种中密切相关元件之间多样性的模型，并发现该家族成员主要在其长末端重复序列（LTR）的U3区域存在差异。通过基于PCR的方法从野生马铃薯Solanum oplocense中获得了Retrosol的全长基因组拷贝。进一步聚焦于扩增拷贝的两个LTR序列进行表征，估计其大约在200万年前插入，从而支持了属分化后转座循环的发生。通过基因组定量PCR确定了茄属物种中Tnt1样元件的拷贝数，结果表明茄属物种中的Retrosol是一种低拷贝数反转录转座子（1 - 4个拷贝），而Retrolyc1在秘鲁茄中具有中等拷贝数（38个拷贝）。反转录转座子含量的比较分析表明，基因组大小或倍性水平与Retrosol拷贝数之间没有相关性。细胞基因组大小为1715 Mbp的四倍体栽培马铃薯每个单倍体基因组的拷贝数与其他二倍体茄属物种（613 - 884 Mbp）相似。相反，秘鲁茄基因组（1125 Mbp）具有更高的拷贝数。这些结果表明，在茄属物种基因组中，关于Tnt1样元件的扩增/活性历史存在谱系特异性的动态变化。
