Tyshenko M G, Walker V K
Department of Biology, Queen's University, Kingston, Ont., Canada.
Biochim Biophys Acta. 1997 Aug 7;1353(2):131-6. doi: 10.1016/s0167-4781(97)00065-1.
The gene encoding the glycolytic enzyme, triosephosphate isomerase (TPI; EC 5.3.1.1), is a favourite model for molecular evolutionists who either subscribe to the theory that introns co-evolved with the ancestral gene, the introns early view, or alternatively, that introns are more recent immigrants. The discovery of an intron in the TPI gene of Culex mosquitoes at a site which was predicted by proponents of the intron early school supported that theory. More recently, the discovery of additional intron sites in several eukaryotes was presented as evidence supporting the introns late school. We have found the 'Culex intron' in two closely related mosquitoes, but not in two more evolutionary primitive Dipterans, suggesting that, if it is an 'ancient intron', loss may be more frequent than that supposed by the intron late school. In addition, we have found that three introns punctuating the TPI gene from the Lepidopteran, Heliothis, appear to be ancestrally related and may be the result of transposable element insertion, 50-90 million years ago. It is argued that both opposing schools in the intron debate be reconciled -- some introns may have been early and certainly others have arrived subsequent to the appearance of the TPI gene.
编码糖酵解酶磷酸丙糖异构酶（TPI；EC 5.3.1.1）的基因，是分子进化学家们喜爱的一个模型，这些进化学家要么支持内含子与祖先基因共同进化的理论（即内含子早期观点），要么支持内含子是近期才出现的观点。在库蚊的TPI基因中发现了一个内含子，其位置与内含子早期学派支持者所预测的一致，这支持了该理论。最近，在几种真核生物中发现了更多内含子位点，被作为支持内含子晚期学派的证据。我们在两种亲缘关系密切的蚊子中发现了“库蚊内含子”，但在另外两种进化上更原始的双翅目昆虫中未发现，这表明，如果它是一个“古老内含子”，那么其丢失可能比内含子晚期学派所认为的更为频繁。此外，我们发现来自鳞翅目昆虫棉铃虫的TPI基因中的三个内含子似乎在祖先上是相关的，可能是5000万到9000万年前转座元件插入的结果。有人认为，内含子争论中的两个对立学派应该调和——一些内含子可能出现得较早，而肯定有其他内含子是在TPI基因出现之后才出现的。
