Laboratoire des Interactions Plantes-Pathogènes, Unité Mixte de Recherche 217, Institut National de la Recherche Agronomique, AgroParisTech, Université Paris 6, Paris, France.
Biometals. 2012 Apr;25(2):423-33. doi: 10.1007/s10534-011-9515-5. Epub 2011 Dec 28.
During infection, the phytopathogenic enterobacterium Dickeya dadantii has to cope with iron-limiting conditions and the production of reactive oxygen species by plant cells. A tight control of the bacterial intracellular iron content is necessary for full virulence of D. dadantii: previous studies have shown that the ferritin FtnA and the bacterioferrtin Bfr, devoted to iron storage, contribute differentially to the virulence of this species. In this work, we investigated the role of the Dps miniferritin in iron homeostasis in D. dadantii. We constructed a Dps-deficient mutant by reverse genetics. This mutant grew like the wild-type stain under iron starvation and showed no decreased iron content. However, the dps mutant displayed an increased sensitivity to hydrogen peroxide in comparison to the wild-type strain. This hydrogen peroxide susceptibility only occurs when bacteria are in the stationary phase. Unlike the bfr and the ftnA mutants, the dps mutant is not affected in its pathogenicity on host plants. The dps gene expression is induced at the stationary phase of growth. The Sigma S transcriptional factor is necessary for this control. Furthermore, dps expression is positively regulated by the oxidative stress response regulator OxyR during the exponential growth phase, after hydrogen peroxide treatment. These results indicate that the Dps miniferritin from D. dadantii has a minor role in iron homeostasis, but is important in conferring tolerance to hydrogen peroxide and for survival of cells that enter the stationary phase of growth.
在感染过程中，植物病原肠杆菌 Dickeya dadantii 必须应对缺铁条件和植物细胞产生的活性氧。细菌细胞内铁含量的严格控制对于 D. dadantii 的完全毒力是必要的：先前的研究表明，铁蛋白 FtnA 和菌铁蛋白 Bfr，专门用于铁储存，对该物种的毒力有不同的贡献。在这项工作中，我们研究了 Dps 小铁蛋白在 D. dadantii 铁平衡中的作用。我们通过反向遗传学构建了 Dps 缺陷突变体。该突变体在缺铁条件下的生长方式与野生型菌株相同，且铁含量没有降低。然而，与野生型菌株相比，dps 突变体对过氧化氢的敏感性增加。这种过氧化氢敏感性仅在细菌处于静止期时发生。与 bfr 和 ftnA 突变体不同，dps 突变体在感染宿主植物时的致病性不受影响。dps 基因的表达在生长的静止期被诱导。Sigma S 转录因子是这种调控所必需的。此外，在指数生长期，dps 表达受过氧化氢处理后的氧化应激反应调节剂 OxyR 的正向调节。这些结果表明，来自 D. dadantii 的 Dps 小铁蛋白在铁平衡中作用较小，但对过氧化氢耐受和进入静止期生长的细胞存活很重要。
