双翅目昆虫(黑腹果蝇和冈比亚按蚊)内含子丢失的比较分析

Analysis of intron loss in Diptera (Drosophila melanogaster and Anopheles gambiae)

内含子插入和丢失的进化动力及机制尚存在许多疑问。通过对真核生物的105个同源基因的蛋白质高度保守区域内含子-外显子结构的研究,对人Homosapiens、小鼠Musmusculus、大鼠Rattusnorvegicus、黑腹果蝇Drosophilamelanogaster、冈比亚按蚊Anophelesgambiae和秀丽隐杆线虫Caenorhabditiselegans的3574个内含子、1001个的内含子保守位点进行分析,推断出不同系统中内含子的变化途径。发现在进化早期,脊椎动物、双翅目昆虫和线虫的共同祖先中含有大量内含子,在进化过程中,双翅目昆虫和线虫发生了大量的内含子丢失,甚至在双翅目昆虫中内含子丢失较线虫更严重。线虫获得的内含子略多于丢失的内含子,而在双翅目昆虫中则显示出内含子的丢失明显多于内含子的获得。该结果合理地解释了内含子在脊椎动物、线虫及昆虫中数量的分布呈下降趋势。

The mechanisms and evolutionary dynamics of intron insert and loss in eukaryotic genes remain poorly understood. Here systematic methods were used to assess the causes of the present-day distribution of introns in different lineage in 105 protein-coding genes containing 3 574 introns and 1 001 intron conserved sites in distinct amino acid alignment sequences in orthologous genes from 6 genomes of vertebrates （Mus musculus , Rattus norvegicus and Homo sapiens ）, Diptera （Drosophila melanogaster and Anopheles gambiae ） and nematode （ Caenorhabditis elegans ）. It was inferred that the common ancestor of vertebrates, Diptera and nematodes hold numerous introns, which were lost in Diptera or nematodes. The loss was even more serious in Diptera than in nematodes. Furthermore, there were a fewer intron gain than loss in nematodes, but there were even more intron loss than gain in Diptera. The results felicitously explain that the number of introns distributed in vertebrates, Diptera and nematodes are declining sequentially.