Studies of the novel retrotransposable elements appeared on rice chromosomes

我们已经鉴定和表征了水稻基因组中具有或不具有LTR的各种反转录转座子。RIRE1是一种拷贝型反转录转座子，最初在野生稻稻稻中发现了大量拷贝。RIRE2、RIRE3和RIRE8分别从桔梗IR36中分离得到。这些元素被证明是具有ltr的吉普赛型反转录转座子，这些元素通常在水稻染色体上彼此嵌套。RIRE2最初被发现是与TrsA相关的序列，TrsA是水稻染色体亚端粒区域的串联重复序列。RIRE2的gag区和pol区与具有ltr的大羚羊反转录转座子Grande1的同源性较高，这些吉普赛型反转录转座子的rt基因氨基酸序列显示它们可分为RIRE3-RIRE8家族和RIRE2-Grande1家族两类。我们还从包括水稻在内的各种高等植物成员中发现了LINE元件，即非ltr反转录转座子。序列分析表明，这些元件含有该区域保守的氨基酸序列基序。系统发育分析表明，这些元件与其他LTR反转录转座子不同，它们是垂直传播的，而其他LTR反转录转座子被认为是水平传播的。

We have identified and characterized various retrotransposons with or without LTR in the genome of O.sativa. RIRE1, a retrotransposon of copia type, was originally found in wild rice O.austrariensis in an extraordinary number of copies. RIRE2, RIRE3 and RIRE8 were isolated from O.sativa IR36. These elements turned out to be retrotransposons of gypsy type with LTR.These elements were often nested one another on rice chromosomes. RIRE2 was originally found as a sequence associated with TrsA,a tandem repeat sequence at the subtelomeric regions of the O.sativa chromosome. The gag and the pol regions of RIRE2 show high homology with those of Grande1, a teosinte retrotransposon with LTR.The amino acid sequences of rt genes of these gypsy-type retrotransposons revealed that they were divided into two groups, such as RIRE3-RIRE8 family and RIRE2-Grande1 family. We have also identified LINE elements, non-LTR retrotransposons, from the various members of the higher plants including rice. Sequence analysis revealed that these elements contained amino acid sequence motifs conserved in the region. Phylogenetic analysis indicated that these elements were transmitted vertically unlike other retrotransposons with LTR,which were believed to be transmitted horizontally.