Hcp2, a Secreted Protein of the Phytopathogen Pseudomonas syringae pv. Tomato DC3000, Is Required for Fitness for Competition against Bacteria and Yeasts
Hcp2, a Secreted Protein of the Phytopathogen Pseudomonas syringae pv. Tomato DC3000, Is Required for Fitness for Competition against Bacteria and Yeasts
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DOI：
10.1128/jb.00611-12
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发表时间：
2012-09-01
影响因子：
3.2
通讯作者：
Lin, Nai-Chun
中科院分区：
文献类型：
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作者：
Haapalainen, Minna;Mosorin, Hanna;Lin, Nai-Chun
在分析植物病原菌假单胞菌致病变种（Pseudomonaserichingae pv.）番茄DC 3000中，我们鉴定出溶血素共调节蛋白（hemolysin-coregulated protein，Hcp）为其中一种分泌蛋白。HCP被认为是VI型分泌系统（T6 SS）的细胞外组分。两个拷贝的hcp基因存在于P.番茄DC 3000基因组hcp 1（PSPTO_2539）和hcp 2（PSPTO_5435）。我们研究了hcp基因的表达模式，并测试了hcp基因敲除突变体在宿主植物定殖和微生物间竞争中的适应性。我们发现，hcp 2基因表达最活跃的生长期和Hcp 2蛋白分泌通过T6 SS和出现在培养基中的共价连接的二聚体。hcp 2的表达在植物中不被诱导，并且不有助于番茄或拟南芥植物的毒力或定殖。相反，hcp 2是在与肠杆菌和酵母菌的竞争中生存所必需的，其功能与抑制这些竞争者的生长有关。这是第一份关于细菌T6 SS相关基因在与酵母竞争中发挥作用的报告。我们的研究结果表明，P. pastingae的T6 SS可能在细菌适应性中发挥重要作用，使这种植物病原体在与其他微生物竞争资源的条件下生存。
When analyzing the secretome of the plant pathogen Pseudomonas syringae pv. tomato DC3000, we identified hemolysin-coregulated protein (Hcp) as one of the secreted proteins. Hcp is assumed to be an extracellular component of the type VI secretion system (T6SS). Two copies of hcp genes are present in the P. syringae pv. tomato DC3000 genome, hcp1 (PSPTO_2539) and hcp2 (PSPTO_5435). We studied the expression patterns of the hcp genes and tested the fitness of hcp knockout mutants in host plant colonization and in intermicrobial competition. We found that the hcp2 gene is expressed most actively at the stationary growth phase and that the Hcp2 protein is secreted via the T6SS and appears in the culture medium as covalently linked dimers. Expression of hcp2 is not induced in planta and does not contribute to virulence in or colonization of tomato or Arabidopsis plants. Instead, hcp2 is required for survival in competition with enterobacteria and yeasts, and its function is associated with the suppression of the growth of these competitors. This is the first report on bacterial T6SS-associated genes functioning in competition with yeast. Our results suggest that the T6SS of P. syringae may play an important role in bacterial fitness, allowing this plant pathogen to survive under conditions where it has to compete with other microorganisms for resources.