Degrave A, Fagard M, Perino C, Brisset M N, Gaubert S, Laroche S, Patrit O, Barny M-A
1Laboratoire des Interactions Plantes Pathogènes UMR 217 INRA/AgroParisTech/UPMC Paris VI, 16 rue Claude Bernard 75005 Paris, France.
Mol Plant Microbe Interact. 2008 Aug;21(8):1076-86. doi: 10.1094/MPMI-21-8-1076.
Erwinia amylovora is the bacterium responsible for fire blight, a necrotic disease affecting plants of the rosaceous family. E. amylovora pathogenicity requires a functional type three secretion system (T3SS). We show here that E. amylovora triggers a T3SS-dependent cell death on Arabidopsis thaliana. The plants respond by inducing T3SS-dependent defense responses, including salicylic acid (SA)-independent callose deposition, activation of the SA defense pathway, reactive oxygen species (ROS) accumulation, and part of the jasmonic acid/ethylene defense pathway. Several of these reactions are similar to what is observed in host plants. We show that the cell death triggered by E. amylovora on A. thaliana could not be simply explained by the recognition of AvrRpt2 ea by the resistance gene product RPS2. We then analyzed the role of type three-secreted proteins (T3SPs) DspA/E, HrpN, and HrpW in the induction of cell death and defense reactions in A. thaliana following infection with the corresponding E. amylovora mutant strains. HrpN and DspA/E were found to play an important role in the induction of cell death, activation of defense pathways, and ROS accumulation. None of the T3SPs tested played a major role in the induction of SA-independent callose deposition. The relative importance of T3SPs in A. thaliana is correlated with their relative importance in the disease process on host plants, indicating that A. thaliana can be used as a model to study their role.
梨火疫病菌是引发火疫病的细菌，火疫病是一种影响蔷薇科植物的坏死性疾病。梨火疫病菌的致病性需要一个功能性的三型分泌系统（T3SS）。我们在此表明，梨火疫病菌在拟南芥上引发了一种依赖T3SS的细胞死亡。植物通过诱导依赖T3SS的防御反应来做出响应，包括水杨酸（SA）非依赖性的胼胝质沉积、SA防御途径的激活、活性氧（ROS）积累以及茉莉酸/乙烯防御途径的一部分。这些反应中的一些与在寄主植物中观察到的情况相似。我们表明，梨火疫病菌在拟南芥上引发的细胞死亡不能简单地用抗性基因产物RPS2对AvrRpt2 ea的识别来解释。然后，我们分析了三型分泌蛋白（T3SPs）DspA/E、HrpN和HrpW在相应的梨火疫病菌突变株感染后拟南芥细胞死亡和防御反应诱导中的作用。发现HrpN和DspA/E在细胞死亡诱导、防御途径激活和ROS积累中起重要作用。所测试的T3SPs均未在SA非依赖性胼胝质沉积的诱导中起主要作用。T3SPs在拟南芥中的相对重要性与其在寄主植物病害过程中的相对重要性相关，这表明拟南芥可作为研究它们作用的模型。
