Pedley Kerry F, Martin Gregory B
Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY 14853, USA.
Annu Rev Phytopathol. 2003;41:215-43. doi: 10.1146/annurev.phyto.41.121602.143032.
The Pto gene in tomato confers gene-for-gene resistance to Pseudomonas syringae pv. tomato, the causative agent of bacterial speck disease. Pto was first introgressed from a wild species of tomato into cultivated tomato varieties over 60 years ago and is now widely used to control speck disease. Cloning of the Pto gene revealed that it encodes a cytoplasmically localized serine-threonine protein kinase. The molecular basis of gene-for-gene recognition in this pathosystem is the direct physical interaction of the Pto kinase with either of two Pseudomonas effector proteins, AvrPto and AvrPtoB. Upon recognition of AvrPto or AvrPtoB, the Pto kinase acts in concert with Prf, a leucine-rich repeat-containing protein, to activate multiple signal transduction pathways. There has been much progress in understanding the evolutionary origin of the Pto gene, structural details about how the Pto kinase interacts with AvrPto and AvrPtoB, signaling steps downstream of Pto, and defense responses activated by the Pto pathway. Future work on this model system will focus on how the interaction of the Pto kinase with bacterial effector proteins activates signal transduction, defining the specific role of signaling components, and ultimately, determining which host defense responses are most responsible for inhibiting growth of the pathogen and suppressing symptoms of bacterial speck disease.
番茄中的Pto基因赋予对丁香假单胞菌番茄致病变种的基因对基因抗性，丁香假单胞菌番茄致病变种是细菌性斑点病的病原体。60多年前，Pto基因首次从番茄的一个野生种渗入到栽培番茄品种中，如今被广泛用于防治斑点病。Pto基因的克隆表明它编码一种定位于细胞质的丝氨酸 - 苏氨酸蛋白激酶。在这个病原系统中基因对基因识别的分子基础是Pto激酶与两种假单胞菌效应蛋白AvrPto和AvrPtoB中的任何一种直接的物理相互作用。在识别AvrPto或AvrPtoB后，Pto激酶与富含亮氨酸重复序列的蛋白Prf协同作用，激活多条信号转导途径。在理解Pto基因的进化起源、Pto激酶与AvrPto和AvrPtoB相互作用的结构细节、Pto下游的信号传导步骤以及Pto途径激活的防御反应方面已经取得了很大进展。关于这个模型系统的未来工作将集中在Pto激酶与细菌效应蛋白的相互作用如何激活信号转导、确定信号传导成分的具体作用，以及最终确定哪些宿主防御反应最有助于抑制病原体生长和抑制细菌性斑点病症状。
