一个新的水稻TE的克隆及其与CACTA转座子结构的比较

对水稻受稻瘟病菌诱导的新因子Rim2的基因组结构进行了研究.以Rim2 cDNA片段作探针, 筛选水稻BAC文库并对其亚克隆, 获得了一个基因组DNA克隆Rim2-569.序列分析表明, Rim2-569序列具备Class 2 转座子的基本结构特征.它两端具有完整的末端颠倒重复(TIRs), 若干正向和反向的亚末端重复 (STRs) , 以及插入位点3 bp的同向重复.它TIRs上的保守序列CACTG有别于以往报道的CACTA转座子.该因子包含一个开读框, 其预测蛋白与CACTA转座子编码的TNP2、TNPD等转座酶有低程度的同源性.该因子没有能够编码类似TNP1/TNPA 的DNA结合蛋白的开读框.Southern杂交显示, Rim2因子在多个不同起源的水稻品种上广泛存在,连同检索结果,证明该家族具有很多拷贝.上述特点表明, 该因子属于一个与CACTA转座子有一定差异的新的转座子大家族.

Cloning of a novel rice TE and its structural comparison with CACTA elements

The genomic structure of the previously reported Rim2 element induced by rice blast pathogen Magnaporthe grisea was studied. By using a Rim2 cDNA probe to screen and subsequently subclone the Rim2 bacterial artificial chromosome, a genomic clone Rim2-569 was obtained. Sequence analysis revealed that Rim2-569 possesses the fundamental structure of Class 2 transposable elements, with perfect terminal inverted repeats in both ends, direct and inverted sub-terminal repeats, along with 3 bp target site duplication. The sequence 'CACTG' in the terminal inverted repeats distinguishes it from reported CACTA elements. The element has a open reading frame encoding a putative transposase that shares low similarity with TNP2, TNPD and other putative transposases of CACTA elements. No open reading frame encoding TNP1/TNPA-like DNA binding protein were found in this element. Southern hybridization showed the ubiquitous distribution of Rim2 elements in rice varieties of different origins, along with data mining, indicating plentiful copies of the element family. These features attest this Rim2 element belonging to a novel transposon family different from the reported CACTA elements.