SanMiguel P, Gaut B S, Tikhonov A, Nakajima Y, Bennetzen J L
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-1392, USA.
Nat Genet. 1998 Sep;20(1):43-5. doi: 10.1038/1695.
Retrotransposons, transposable elements related to animal retroviruses, are found in all eukaryotes investigated and make up the majority of many plant genomes. Their ubiquity points to their importance, especially in their contribution to the large-scale structure of complex genomes. The nature and frequency of retro-element appearance, activation and amplification are poorly understood in all higher eukaryotes. Here we employ a novel approach to determine the insertion dates for 17 of 23 retrotransposons found near the maize adh1 gene, and two others from unlinked sites in the maize genome, by comparison of long terminal repeat (LTR) divergences with the sequence divergence between adh1 in maize and sorghum. All retrotransposons examined have inserted within the last six million years, most in the last three million years. The structure of the adh1 region appears to be standard relative to the other gene-containing regions of the maize genome, thus suggesting that retrotransposon insertions have increased the size of the maize genome from approximately 1200 Mb to 2400 Mb in the last three million years. Furthermore, the results indicate an increased mutation rate in retrotransposons compared with genes.
逆转座子是与动物逆转录病毒相关的可移动元件，在所有已研究的真核生物中都能找到，并且在许多植物基因组中占大多数。它们的普遍存在表明了它们的重要性，特别是在它们对复杂基因组的大规模结构的贡献方面。在所有高等真核生物中，逆转元件出现、激活和扩增的性质和频率都了解得很少。在这里，我们采用一种新方法，通过比较长末端重复序列（LTR）的差异与玉米和高粱中adh1基因之间的序列差异，来确定在玉米adh1基因附近发现的23个逆转座子中的17个以及来自玉米基因组中不连锁位点的另外两个逆转座子的插入日期。所有检测的逆转座子都是在过去600万年中插入的，大多数是在过去300万年中插入的。相对于玉米基因组的其他含基因区域，adh1区域的结构似乎是标准的，因此表明在过去300万年中，逆转座子的插入使玉米基因组的大小从大约1200兆碱基增加到了2400兆碱基。此外，结果表明逆转座子的突变率比基因的突变率更高。
