Kidwell M G, Lisch D
Department of Ecology and Evolutionary Biology and The Center for Insect Science, University of Arizona, Tucson, AZ 85721, USA.
Proc Natl Acad Sci U S A. 1997 Jul 22;94(15):7704-11. doi: 10.1073/pnas.94.15.7704.
A tremendous wealth of data is accumulating on the variety and distribution of transposable elements (TEs) in natural populations. There is little doubt that TEs provide new genetic variation on a scale, and with a degree of sophistication, previously unimagined. There are many examples of mutations and other types of genetic variation associated with the activity of mobile elements. Mutant phenotypes range from subtle changes in tissue specificity to dramatic alterations in the development and organization of tissues and organs. Such changes can occur because of insertions in coding regions, but the more sophisticated TE-mediated changes are more often the result of insertions into 5' flanking regions and introns. Here, TE-induced variation is viewed from three evolutionary perspectives that are not mutually exclusive. First, variation resulting from the intrinsic parasitic nature of TE activity is examined. Second, we describe possible coadaptations between elements and their hosts that appear to have evolved because of selection to reduce the deleterious effects of new insertions on host fitness. Finally, some possible cases are explored in which the capacity of TEs to generate variation has been exploited by their hosts. The number of well documented cases in which element sequences appear to confer useful traits on the host, although small, is growing rapidly.
关于自然种群中转座元件（TEs）的种类和分布，正在积累大量的数据。毫无疑问，TEs在规模和复杂性上提供了前所未有的新遗传变异。有许多与移动元件活性相关的突变和其他类型遗传变异的例子。突变表型范围从组织特异性的细微变化到组织和器官发育及组织的剧烈改变。这些变化可能由于编码区的插入而发生，但更复杂的TE介导的变化更常是插入到5'侧翼区域和内含子的结果。在这里，从三个并非相互排斥的进化角度来审视TE诱导的变异。首先，研究由TE活性的内在寄生性质导致的变异。其次，我们描述元件与其宿主之间可能的共同适应，这种共同适应似乎是由于选择以减少新插入对宿主适应性的有害影响而进化而来的。最后，探讨了一些可能的情况，即宿主利用TE产生变异的能力。尽管记录良好的元件序列似乎赋予宿主有用性状的案例数量不多，但正在迅速增加。
