The type III effectors HsvG and HsvB of gall-forming Pantoea agglomerans determine host specificity and function as transcriptional activators
The type III effectors HsvG and HsvB of gall-forming Pantoea agglomerans determine host specificity and function as transcriptional activators
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DOI：
10.1111/j.1365-2958.2006.05301.x
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发表时间：
2006-09-01
影响因子：
3.6
通讯作者：
Barash, Isaac
中科院分区：
文献类型：
--
作者：
Nissan, Gal;Manulis-Sasson, Shulamit;Barash, Isaac
成团泛菌 pv. gypsophilae (Pag) 在满天星上引起瘿并对甜菜产生过敏反应，而 P. agglomerans pv. betae (Pab) 会在甜菜和满天星上诱导虫瘿。两种病理变型的致病性均依赖于含有 III 型分泌系统 (TTSS) 成分和效应子的质粒的存在。 Pag (HsvG-Pag) 和 Pab (HsvG-Pab) 的 HsvG TTSS 效应子决定了两种病理变型对满天星的宿主特异性。在这里，我们描述了一种新的 HsvG 同源物 HsvB，它决定了 Pag 和 Pab 对甜菜的宿主特异性。 HsvG 需要两个直接氨基酸重复序列才能对满天星产生致病性，而 HsvB 中的一个重复序列足以对甜菜产生致病性。 HsvG-Pag 和 HsvB-Pab 之间的重复序列交换导致宿主特异性的转换。 GFP-HsvG 或 GFP-HsvB 融合体在满天星、甜菜或瓜叶中的瞬时表达表明 HsvG 和 HsvB 定位于宿主和非宿主植物的细胞核。酵母单杂交测定表明，HsvG 或 HsvB 的单个重复足以激活转录。通过采用随机结合位点选择和凝胶迁移测定，HsvG 被证明是一种具有 ACACC/aAA 共有结合位点的双链 DNA 结合蛋白。这些结果表明 HsvG 和 HsvB 是宿主特异性决定因素，并且具有影响宿主转录机制的潜力。
Pantoea agglomerans pv. gypsophilae (Pag) elicits galls on gypsophila and a hypersensitive response on beet, whereas P. agglomerans pv. betae (Pab) induces galls on both beet and gypsophila. The pathogenicity of both pathovars is dependent on the presence of a plasmid harbouring type III secretion system (TTSS) components and effectors. The HsvG TTSS effectors of Pag (HsvG-Pag) and Pab (HsvG-Pab) determine the host specificity of both pathovars on gypsophila. Here we describe a novel HsvG homologue, HsvB, which determines the host specificity of Pag and Pab on beet. HsvG requires two direct amino acid repeats for pathogenicity on gypsophila, whereas one repeat in HsvB is sufficient for pathogenicity on beet. Exchanging repeats between HsvG-Pag and HsvB-Pab resulted in a switch of host specificities. Transient expression of GFP-HsvG or GFP-HsvB fusions in gypsophila, beet or melon leaves showed that HsvG and HsvB were localized to the nuclei of host and non-host plants. A yeast one-hybrid assay revealed that a single repeat of HsvG or HsvB was sufficient to activate transcription. By employing random binding-site selection and gel-shift assay HsvG was demonstrated to be a double-stranded DNA-binding protein with an ACACC/aAA consensus binding site. These results suggest that HsvG and HsvB are host-specificity determinants and bear the potential to affect the host transcriptional machinery.