Université de Poitiers, UMR CNRS 6556 Ecologie Evolution Symbiose, 40 Avenue du Recteur Pineau, Poitiers, France.
Evolution. 2011 Nov;65(11):3327-31. doi: 10.1111/j.1558-5646.2011.01395.x. Epub 2011 Sep 13.
The distribution, dynamics, and evolution of insertion sequences (IS), the most frequent class of prokaryotic transposable elements, are conditioned by their ability to horizontally transfer between cells. IS horizontal transfer (HT) requires shuttling by other mobile genetic elements. It is widely assumed in the literature that these vectors are phages and plasmids. By examining the relative abundance of IS in 454 plasmid and 446 phage genomes, we found that IS are very frequent in plasmids but, surprisingly, very rare in phages. Our results indicate that IS rarity in phages reflects very strong and efficient postinsertional purifying selection, mainly caused by a higher density of deleterious insertion sites in phages compared to plasmids. As they do not tolerate IS insertions, we conclude that phages may be rather poor vectors of IS HT in prokaryotes, in sharp contrast with the conventional view.
插入序列（IS）是原核可移动元件中最常见的一类，其分布、动态和进化受到其在细胞间水平转移能力的制约。IS 的水平转移（HT）需要通过其他移动遗传元件进行转导。文献中广泛认为这些载体是噬菌体和质粒。通过比较 454 个质粒和 446 个噬菌体基因组中 IS 的相对丰度，我们发现 IS 在质粒中非常普遍，但令人惊讶的是，在噬菌体中却非常罕见。我们的研究结果表明，噬菌体中 IS 的稀有性反映了非常强烈和有效的插入后净化选择，主要是由于噬菌体中与质粒相比，有害插入位点的密度更高。由于噬菌体不能容忍 IS 的插入，因此我们得出结论，噬菌体可能不是原核生物中 IS HT 的良好载体，这与传统观点形成鲜明对比。
