Cooperative Research Centre for National Plant Biosecurity, 621 Burwood Hwy, Knoxfield, VIC 3180, Australia.
Gene. 2012 Aug 1;504(1):6-12. doi: 10.1016/j.gene.2012.05.002. Epub 2012 May 11.
The Hrp pathogenicity island (hrpPAI) of Erwinia amylovora not only encodes a type III secretion system (T3SS) and other genes required for pathogenesis on host plants, but also includes the so-called island transfer (IT) region, a region that originates from an integrative conjugative element (ICE). Comparative genomic analysis of the IT regions of two Spiraeoideae- and three Rubus-infecting strains revealed that the regions in Spiraeoideae-infecting strains were syntenic and highly conserved in length and genetic information, but that the IT regions of the Rubus-infecting strains varied in gene content and length, showing a mosaic structure. None of the ICEs in E. amylovora strains were complete, as conserved ICE genes and the left border were missing, probably due to reductive genome evolution. Comparison of the hrpPAI region of E. amylovora strains to syntenic regions from other Erwinia spp. indicates that the hrpPAI and the IT regions are the result of several insertion and deletion events that have occurred within the ICE. It also suggests that the T3SS was present in a common ancestor of the pathoadapted Erwinia spp. and that insertion and deletion events in the IT region occurred during speciation.
植物病原欧文氏菌的 Hrp 致病性岛（hrpPAI）不仅编码了一种 III 型分泌系统（T3SS）和在宿主植物上致病所需的其他基因，还包括所谓的岛转移（IT）区域，该区域源自整合共轭元件（ICE）。对两个感染蔷薇科和三个感染悬钩子属的菌株的 IT 区进行比较基因组分析表明，感染蔷薇科的菌株的区域在基因内容和长度上具有同源性且高度保守，但感染悬钩子属的菌株的 IT 区在基因内容和长度上存在差异，表现出镶嵌结构。植物病原欧文氏菌菌株中的任何 ICE 都不完整，因为缺少保守的 ICE 基因和左边界，这可能是由于基因组的简化进化所致。将植物病原欧文氏菌菌株的 hrpPAI 区域与其他欧文氏菌属的同源区域进行比较表明，hrpPAI 和 IT 区域是 ICE 内发生的多次插入和缺失事件的结果。这也表明，T3SS 存在于适应病原的欧文氏菌属的共同祖先中，而 IT 区域的插入和缺失事件则发生在物种形成过程中。
