水稻基因组中一类具有潜在转座活性的Solo—LTR的结构分析和鉴定

在水稻4号染色体两个BAC克隆序列分析中，发现了两个solo-LTR，分别命名为SLTR1和SLTR2。它们分别位于水稻18S rRNA基因和一逆转座子内部。序列比较发现，SLTR1和SLTR2存在着较高的同源性，并与水稻逆转座子RIRE8的LTR序列高度同源，分别为89.1%和70.1%。它们属于一类水稻gypsy类型逆转座子。利用SLTR1和SLTR2与水稻DNA杂交，结果显示两者广泛分布于水稻基因组中，是一类高拷贝重复序列。分别利用SLTR1和SLTR2的两侧特异性序列设计引物进行PCR扩增，结果发现在基因组的相应位置并不存在SLTR1或SLTR2；利用它们两侧被打断基因的特异性片段杂交基因组DNA，得到了同样的结果。这意味着SLTR1和SLTR2来源于基因组的其它位置，并通过某种转座的过程进入18S rRNA基因和另一逆转座子内部。Solo-LTR存在着这种潜在的转座活性，对于进一步研究solo-LTR的来源以及其在基因组进货和基因的表达调控中具有一定的意义。

Identification and Structural Analysis of a Class of Potentially Transposable Solo-LTR in Rice Genome

Two solo LTRs, named SLTR1 and SLTR2, were found in BAC t17804 and q5343 on rice chromosome 4, respectively. SLTR1 is in a 18 S rRNA gene and SLTR2 is in a retrotransposon. They share sequence homology and show sequence similarity 89.1% and 70.1% to the LTR of rice retrotransposon RIRE8, respectively. SLTR1 and SLTR2 are of gypsy retrotransposons of rice. They are both highly repetitive sequences and widely distributed in the rice genome, as shown by hybridization with specific probes of SLTR1 and SLTR2. Using PCR amplication with primers on flanking sequences of SLTR1 and SLTR2, no bands corres ponding to those of BACs were amplified using the rice genomic DNA as template. SLTR1 and SLTR2 did not locate in the relative loci of the rice genome, as supported by hybridization with specific probes of genes interrupted by them. Obviously, SLTR1 and SLTR2 reported here came from different loci of the genome by the transposition. These solo LTRs may be useful for our rice genome studies.