Department of Plant Pathology, Cornell University, Ithaca, NY 14853, USA.
Mol Plant Pathol. 2005 Mar 1;6(2):125-38. doi: 10.1111/j.1364-3703.2005.00269.x.
SUMMARY Sequence analysis of the region bordering the hrp/dsp gene cluster of Erwinia amylovora strain Ea321, which causes fire blight, revealed characteristics of pathogenicity islands (PAIs). Included are genes for a phage integrase, a tRNA(Phe), several orthologues of genes of YAPI, a PAI of Yersinia pseudotuberculosis, and several putative virulence genes with HrpL-dependent promoter motifs. The island is designated the Hrp PAI of E. amylovora. It is comprised of a chromosomal region of c. 62 kb with 60 open reading frames (ORFs). Comparison of the Hrp PAI of E. amylovora with those of four closely related bacteria showed that orfB, a homologue of avrBsT of Xanthomonas campestris pv. vesicatoria, and orfA, its putative chaperone gene, are present only in the Hrp PAI of E. amylovora. As regions flanking the hrp/dsp gene cluster are quite diverse, addition and deletion may have occurred during divergent evolution of the five bacteria. Among ORFs of the PAI of Ea321, three new HrpL-dependent genes were identified. Because they are required for full virulence in apple, they were designated hsvC, hsvB and hsvA (hrp-associated systemic virulence). They encode a homologue of an amidinotransferase for phaseolotoxin biosynthesis and homologues of a nikkomycin-biosynthetic protein of Pseudomonas syringae.
火疫病病原菌韧皮部杆菌 Ea321 菌株的 Hrp/dsp 基因簇边界区序列分析揭示了致病性岛（PAI）的特征。该岛包含噬菌体整合酶、tRNA(Phe)、YAPI 基因的几个同源物、假结核耶尔森氏菌的 PAI 以及几个具有 HrpL 依赖性启动子基序的推定毒力基因。该岛被指定为韧皮部杆菌的 Hrp PAI。它由一个约 62kb 的染色体区域组成，包含 60 个开放阅读框（ORFs）。将 E. amylovora 的 Hrp PAI 与四个密切相关的细菌进行比较表明，orfB，即野油菜黄单胞菌 pv.vesicatoria 的 avrBsT 的同源物，以及 orfA，其推定的伴侣基因，仅存在于 E. amylovora 的 Hrp PAI 中。由于 Hrp/dsp 基因簇侧翼区域非常多样化，因此在这五种细菌的分化进化过程中可能发生了添加和缺失。在 Ea321 的 PAI 的 ORFs 中，鉴定出三个新的 HrpL 依赖性基因。由于它们是苹果完全毒力所必需的，因此被命名为 hsvC、hsvB 和 hsvA（与 Hrp 相关的系统性毒力）。它们编码一个用于豆科植物毒素生物合成的酰胺转移酶同源物和 Pseudomonas syringae 的 nikkomycin 生物合成蛋白的同源物。
