Studied on gypsy-type retrotransposons in plant ; their stuructural diversity and their choromosomal localization

通过对水稻（RIRE3、RIRE8和RIRE2）以及各种植物（单子叶、双子叶、松树、银杏、马尾、苔类和藻类）中gypsey型反转录转座子的rt基因的系统发育分析，这些反转录转座子同源物可分为两个家族，在每个家族中又分为几个亚家族。这表明垂直传播过程中的序列分化是影响植物gypsy型反转录转座子进化的主要因素。另一个水稻吉普赛型反转录转座子名为RIRE7，是一个反转录转座子，其重量与谷物染色体着丝粒区域的几个DNA片段同源。RIRE7也被插入到单位长度为155bp的串联重复序列TrsD的一个位点上。*中期染色体的FISH分析。结果表明，RIRE7和TrsD序列均存在于染色体的着丝粒区。对水稻粗线染色体的进一步FISH分析表明，TrsD序列位于近中心异染色质区。这些发现有力地表明，RIRE7和TrsD是水稻染色体近中心异染色质的重要组成部分。

Phylogenetic analysis of the rt genes of gypsy-type retrotransposons from rice (RIRE3, RIRE8 and RIRE2) as well as various plants (monocots, dicots, pine, ginkgo, horsetail, liverwort and algae) showed that these retrotransposon homologues could be classified into two families, in each of which, they were further classified into several subfamilies. This indicates that sequence divergence during vertical transmission has been a major influence on the evolution of gypsy-type retrotransposons in plants. An another rice gypsy-type retrotranson, named RIRE7, is a retrotransposon wigh homology to several DNA segaments present in the centromere regions of cereal chromosomes. RIRE7 were also found to be inserted into a site within a tandem repeat sequence with a unit length of 155bp, named TrsD. FISH analysis of the metaphase chromosomes of *. sativa showed that both RIRE7 and TrsD sequences were present in the centromere region of the chromosomes. Further FISH analysis of rice pachytene chromosomes showed that the TrsD sequences were located in a pericentromeric heterochromatin region. These findings strongly sugge that RIRE7, as well as TrsD, is an important component of the pericentromeric heterochromatin of rice chromosomes.