Sequence relationship of retrotransposable elements R1 and R2 within and between divergent insect species.
Sequence relationship of retrotransposable elements R1 and R2 within and between divergent insect species.
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不同昆虫物种内部和之间逆转录转座元件 R1 和 R2 的序列关系。
DOI：
10.1093/oxfordjournals.molbev.a039990
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发表时间：
1993
影响因子：
10.7
通讯作者：
Eickbush,TH
中科院分区：
文献类型：
--
作者：
Burke,WD;Eickbush,DG;Xiong,Y;Jakubczak,J;Eickbush,TH
R1和R2是整合在家蚕和黑腹果蝇28 S核糖体RNA（rRNA）基因特定位点的反转录转座因子。我们以前已经表明，大多数昆虫物种包含在其28 S基因在R1和/或R2位点的插入。我们已经测序了来自三种其他昆虫物种的R1和R2元件的3'端半部分：真菌小蠊，粪蝇Sciara coprophila（双翅目）;日本甲虫，日本金龟子Popillia japonica（鞘翅目）;和寄生蜂Nasonia vitripennis（膜翅目）。通过筛选含有rDNA单位的λ噬菌体基因组克隆，并通过聚合酶链反应方法，使用针对逆转录酶结构域中保守序列的简并引物，与针对插入位点3'的28 S基因的第二引物组合，获得元件。从四个昆虫目的R1和R2的序列的比较表明，其开放阅读框的组织已被保存，因此很可能是类似的整个昆虫。该序列分析还表明，除了在反转录转座过程本身期间产生的5'截短之外，大多数元件没有使它们失活的累积突变。Popillia japonica和N.丽翅凤蝶与以前描述的物种不同之处在于：（a）日本丽翅凤蝶含有多个R2科;丽翅凤蝶含有多个R1家族。这些不同家族之间的核苷酸序列同一性低。它们的开放阅读框的氨基酸序列的一致性平均只有41%的P. japonica和35%的N.R1家庭。丽翅凤蝶在一个物种内存在多个高度分化的家族的元素表明，每个插入家族能够保持其拷贝数，而不会消除其他家族在其竞争有限数量的28 S基因，或有广泛的水平转移的R1和R2元件昆虫物种之间。
R1 and R2 are retrotransposable elements that integrate at specific sites in the 28S ribosomal RNA (rRNA) genes of Bombyx mori and Drosophila melanogaster. We have previously shown that most insect species contain insertions in their 28S genes at the R1 and/or R2 site. We have sequenced the 3' half of R1 and R2 elements from three additional insect species: the fungus gnat, Sciara coprophila (Diptera); the Japanese beetle, Popillia japonica (Colleoptera); and the parasitic wasp, Nasonia vitripennis (Hymenoptera). The elements were obtained by screening lambda phage genomic clones containing rDNA units and by a polymerase chain reaction approach using degenerate primers to conserved sequences in the reverse-transcriptase domain, in combination with a second primer to the 28S gene 3' of the insertion site. Comparisons of the sequences of R1 and R2 from four insect orders suggest that the organization of their open-reading frames has been conserved and is therefore likely to be similar throughout insects. This sequence analysis also indicates that, except for 5' truncations generated during the retrotransposition process itself, most elements have not accumulated mutations that would make them inactive. Popillia japonica and N. vitripennis differed from previously described species, in that (a) P. japonica contained multiple families of R2 and (b) N. vitripennis contained multiple families of R1. Nucleotide sequence identity between these different families is low. Amino acid sequence identity of their open-reading frames averaged only 41% for the R2 families of P. japonica and 35% for the R1 families of N. vitripennis. The presence of multiple highly divergent families of elements within a species suggests either that each insertion family is able to maintain its copy number without eliminating the other families in its competition for a limited number of 28S genes or that there has been extensive horizontal transfer of R1 and R2 elements between insect species.