A bacterial genetic screen identifies functional coding sequences of the insect mariner transposable element Famar1 amplified from the genome of the earwig, Forficula auricularia
A bacterial genetic screen identifies functional coding sequences of the insect mariner transposable element Famar1 amplified from the genome of the earwig, Forficula auricularia
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DOI：
10.1534/genetics.166.2.823
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发表时间：
2004-02-01
期刊：
影响因子：
3.3
通讯作者：
Lampe, DJ
中科院分区：
文献类型：
--
作者：
Barry, EG;Witherspoon, DJ;Lampe, DJ
水手家族的转座子广泛存在于动物基因组中，并且显然是通过水平转移感染了它们。大多数物种只携带特定水手转座子的旧有缺陷副本，这些副本与其活跃的水平转移祖先有很大差异，而少数物种则含有年轻的、非常相似的活跃副本。我们在这里报告了在细菌中使用全基因组筛选来从欧洲蠼螋（Forficula aurillaryia）中分离出稍微不同的 Famar1 拷贝，这些拷贝编码功能性转座酶。对欧洲蜜蜂 Apis mellifera 的 Famar1 的功能性和非功能性编码序列以及 Ammar1 的非功能性拷贝进行了测序，以检查其分子进化。在源自这些序列的树的任何分支中都没有检测到序列保守的选择，甚至在导致功能性拷贝的分支上也没有检测到。这与当前的水手转座子进化模型一致，该模型期望在特定宿主内进行中性进化，只有在水平转移到新宿主时才会发生功能选择。我们的结果进一步表明，水手并不是经过微调的遗传实体，并且在单一宿主谱系的功能拷贝中可能会发生比以前认识到的更大量的序列多样化。最后，这种分离活性拷贝的方法可用于分离其他新型活性转座子，而无需重建祖先序列。
Transposons of the mariner family are widespread in animal genomes and have apparently infected them by horizontal transfer. Most species carry only old defective copies of particular mariner transposons that have diverged greatly from their active horizontally transferred ancestor, while a few contain young, very similar, and active copies. We report here the use of a whole-genome screen in bacteria to isolate somewhat diverged Famar1 copies from the European earwig, Forficula auricularia, that encode functional transposases. Functional and nonfunctional coding sequences of Famar1 and nonfunctional copies of Ammar1 from the European honey bee, Apis mellifera, were sequenced to examine their molecular evolution. No selection for sequence conservation was detected in any clade of a tree derived from these sequences, not even on branches leading to functional copies. This agrees with the current model for mariner transposon evolution that expects neutral evolution within particular hosts, with selection for function occurring only upon horizontal transfer to a new host. Our results further suggest that mariners are not finely tuned genetic entities and that a greater amount of sequence diversification than had previously been appreciated can occur in functional copies in a single host lineage. Finally, this method of isolating active copies can be used to isolate other novel active transposons without resorting to reconstruction of ancestral sequences.