The vlhA loci of Mycoplasma synoviae are confined to a restricted region of the genome
The vlhA loci of Mycoplasma synoviae are confined to a restricted region of the genome
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DOI：
10.1099/mic.0.27109-0
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发表时间：
2005-03-01
期刊：
影响因子：
2.8
通讯作者：
Browning, GF
中科院分区：
文献类型：
--
作者：
Allen, JL;Noormohammadi, AH;Browning, GF
滑膜支原体是家禽的主要病原体，它含有一个表达的全长vlhA基因，编码其血凝素，以及大量的vlhA伪核基因，它们可以被多个位点特异性重组事件招募来产生表达基因的嵌合体变体。VlhA假基因区的位置和分布以及它们与表达基因的关系尚未被研究。为了确定这些区域之间的关系，利用限制性内切酶Smal、I-Ceul、BsiWI、APAL和XHOL以及rRNA、recA和Tufa的放射性标记探针构建了滑膜分枝杆菌基因组的物理图谱。用克隆的编码vlhA基因独特部分的片段和含有ORF 3和ORF 6 vlhA假基因保守区的两个PCR产物在图谱上定位含有这些基因的区域。滑膜支原体的染色体大小为890(？)4kb，两个rRNA操纵子方向相同。表达的vlhA基因和vlhA假基因均位于染色体上相同的114kb区域。这些发现表明，与鸡败血支原体不同的是，vlhA基因位于染色体周围的几个位置，抗原变异是通过交替转录40多个翻译活性基因而产生的，而滑膜支原体的所有vlhA序列都聚集在一起，这表明需要密切接近才能促进用于产生表达的vlhA基因多样性的位点特异性重组。
Mycoplasma synoviae, a major pathogen of poultry, contains a single expressed, full-length vlhA gene encoding its haernagglutinin, and a large number of vlhA pseuclogenes that can be recruited by multiple site-specific recombination events to generate chimaeric variants of the expressed gene. The position and distribution of the vlhA pseudogene regions, and their relationship with the expressed gene, have not been investigated. To determine the relationship between these regions, a physical map of the M. synoviae genome was constructed using the restriction endonucleases Smal, I-Ceul, BsiWI, Apal and Xhol and radiolabelled probes for rrnA, recA and tufA. A cloned fragment encoding the unique portion of the expressed vlhA gene and two PCR products containing conserved regions of the ORF 3 and ORF 6 vlhA pseudogenes were used to locate the regions containing these genes on the map. The chromosome of M. synoviae was found to be 890(.)4 kb and the two rRNA operons were in the same orientation. Both the expressed vlhA gene and the vlhA pseudogenes were confined to the same 114 kb region of the chromosome. These findings indicate that, unlike Mycoplasma gallisepticum, in which the vlhA genes are located in several loci around the chromosome and in which antigenic variation is generated by alternating transcription of over 40 translationally competent genes, M. synoviae has all of the vlhA sequences clustered together, suggesting that close proximity is needed to facilitate the site-specific recombinations used to generate diversity in the expressed vlhA gene.