Da Lage J L, Wegnez M, Cariou M L
UPR 9034: Populations, Génétique et Evolution, CNRS, 91198 Gif sur Yvette cedex, France.
J Mol Evol. 1996 Oct;43(4):334-47. doi: 10.1007/BF02339008.
While the two amylase genes of Drosophila melanogaster are intronless, the three genes of D. pseudoobscura harbor a short intron. This raises the question of the common structure of the Amy gene in Drosophila species. We have investigated the presence or absence of an intron in the amylase genes of 150 species of Drosophilids. Using polymerase chain reaction (PCR), we have amplified a region that surrounds the intron site reported in D. pseudoobscura and a few other species. The results revealed that most species contain an intron, with a variable size ranging from 50 to 750 bp, although the very majoritary size was around 60-80 bp. Several species belonging to different lineages were found to lack an intron. This loss of intervening sequence was likely due to evolutionarily independent and rather frequent events. Some other species had both types of genes: In the obscura group, and to a lesser extent in the ananassae subgroup, intronless copies had much diverged from intron-containing genes. Base composition of short introns was found to be variable and correlated with that of the surrounding exons, whereas long introns were all A-T rich. We have extended our study to non-Drosophilid insects. In species from other orders of Holometaboles, Lepidoptera and Hymenoptera, an intron was found at an identical position in the Amy gene, suggesting that the intron was ancestral.
黑腹果蝇的两个淀粉酶基因没有内含子，而拟暗果蝇的三个基因含有一个短内含子。这就引出了果蝇物种中Amy基因共同结构的问题。我们研究了150种果蝇的淀粉酶基因中内含子的有无情况。利用聚合酶链反应（PCR），我们扩增了拟暗果蝇和其他一些物种中报道的内含子位点周围的区域。结果显示，大多数物种都含有一个内含子，其大小可变，范围从50到750碱基对，不过绝大多数大小在60 - 80碱基对左右。发现属于不同谱系的几个物种没有内含子。这种间隔序列的缺失可能是由于进化上独立且相当频繁的事件导致的。其他一些物种有两种类型的基因：在果蝇的obscura组，以及在较小程度上在ananassae亚组中，无内含子的拷贝与含内含子的基因有很大差异。发现短内含子的碱基组成是可变的，并且与周围外显子的碱基组成相关，而长内含子都富含A - T。我们将研究扩展到了非果蝇类昆虫。在全变态类的其他目，鳞翅目和膜翅目的物种中，在Amy基因的相同位置发现了一个内含子，这表明该内含子是祖先型的。
