The genome of the heartwater agent Ehrlichia ruminantium contains multiple tandem repeats of actively variable copy number
The genome of the heartwater agent Ehrlichia ruminantium contains multiple tandem repeats of actively variable copy number
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DOI：
10.1073/pnas.0406633102
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发表时间：
2005-01-18
影响因子：
11.1
通讯作者：
Allsopp, BA
中科院分区：
文献类型：
--
作者：
Collins, NE;Liebenberg, J;Allsopp, BA
Heartwater是一种由蜱传播的家畜和野生反刍动物疾病，由细胞内的Rickettsia Ehrlichia ruminantium（以前称为Cowdria ruminantium）引起。它是整个撒哈拉以南非洲畜牧业生产的一个主要制约因素，并有入侵美洲的威胁，但目前还没有有效疫苗的前景。进行了鸟枪基因组测序项目，期望获得生物体的完整蛋白质编码库将有助于寻找疫苗候选基因。我们在这里报告完整的1，516，355-bp序列的模式菌株，股票来自南非Welgevonden分离。预测基因组中只有62%是编码序列，编码888种蛋白质和41种稳定的RNA。最显著的特点是大量串联重复和重复序列，一些连续可变的拷贝数，这有助于低比例的编码序列。这些重复序列介导了许多易位和倒位事件，导致一些基因的复制和截短，也产生了新的基因。有32个预测的假基因，其中大部分是与重复相关的基因的截短片段。这些假基因不是在其他细胞内细菌中看到的还原进化的结果，而是正在进行的序列复制事件的产物。
Heartwater, a tick-borne disease of domestic and wild ruminants, is caused by the intracellular rickettsia Ehrlichia ruminantium (previously known as Cowdria ruminantium). It is a major constraint to livestock production throughout subSaharan Africa, and it threatens to invade the Americas, yet there is no immediate prospect of an effective vaccine. A shotgun genome sequencing project was undertaken in the expectation that access to the complete protein coding repertoire of the organism will facilitate the search for vaccine candidate genes. We report here the complete 1,516,355-bp sequence of the type strain, the stock derived from the South African Welgevonden isolate. Only 62% of the genome is predicted to be coding sequence, encoding 888 proteins and 41 stable RNA species. The most striking feature is the large number of tandemly repeated and duplicated sequences, some of continuously variable copy number, which contributes to the low proportion of coding sequence. These repeats have mediated numerous translocation and inversion events that have resulted in the duplication and truncation of some genes and have also given rise to new genes. There are 32 predicted pseudogenes, most of which are truncated fragments of genes associated with repeats. Rather then being the result of the reductive evolution seen in other intracellular bacteria, these pseudogenes appear to be the product of ongoing sequence duplication events.