Choe C P, Hwang U W, Kim W
Department of Molecular Biology, Seoul National University, Korea.
Mol Cells. 1999 Apr 30;9(2):191-9.
We constructed the putative secondary structures of the small subunit rRNAs (SSU rRNA) from three strepsipteran insects. The primary sequences of the strepsipteran SSU rRNAs are unusually long due to unique and long insertions. In spite of these insertions, the basic shapes of their secondary structures are well maintained as shown in those of other eukaryotes, because these insertions appear mainly in the variable regions. The secondary structures for the V1, V3, V5, V8, and V9 regions are well conserved, even though the primary structures of V1, V5, and V8 regions are quite variable. However, the predicted secondary structures for the V2, V4, and V7 regions are quite different from those of other insects. In the V4 and V7 regions, helices specific to the Strepsiptera exist. These helices have not been reported in other organisms so far. Similarly, four eukaryotic specific helices (E8-1, E10-2, E23-4 and E45-1) not reported in insects exist in the V2, V4, and V8 regions. These helices are formed by the inserted sequences. The secondary structures of the expanded segments of the strepsipteran SSU rRNA were applied to infer the phylogenetic position of Strepsiptera, one of the most enigmatic problems in insect phylogeny. Only the secondary structure of the V7 region showed the weak Strepsiptera/Diptera sister-group relationship.
我们构建了三种捻翅目昆虫小亚基核糖体RNA（SSU rRNA）的推测二级结构。由于独特且长的插入序列，捻翅目SSU rRNA的一级序列异常长。尽管有这些插入序列，但正如其他真核生物的情况所示，它们二级结构的基本形状仍得到很好的保留，因为这些插入序列主要出现在可变区。V1、V3、V5、V8和V9区的二级结构高度保守，尽管V1、V5和V8区的一级结构变化很大。然而，V2、V4和V7区的预测二级结构与其他昆虫的二级结构有很大不同。在V4和V7区，存在捻翅目特有的螺旋结构。到目前为止，这些螺旋结构在其他生物中尚未见报道。同样，在V2、V4和V8区存在昆虫中未报道的四个真核生物特有的螺旋结构（E8 - 1、E10 - 2、E23 - 4和E45 - 1）。这些螺旋结构由插入序列形成。捻翅目SSU rRNA扩展片段的二级结构被用于推断捻翅目的系统发育位置，这是昆虫系统发育中最具谜团的问题之一。只有V7区的二级结构显示出捻翅目/双翅目较弱的姐妹群关系。
