Jia Y, Loh Y T, Zhou J, Martin G B
Department of Agronomy, Purdue University, West Lafayette, Indiana 47907-1150, USA.
Plant Cell. 1997 Jan;9(1):61-73. doi: 10.1105/tpc.9.1.61.
The Pto gene was derived originally from the wild tomato species Lycopersicon pimpinellifolium and confers resistance to Pseudomonas syringae pv tomato strains expressing the avirulence gene avrPto. The Fen gene is also derived from L. pimpinellifolium and confers sensitivity to the insecticide fenthion. We have now isolated and characterized the alleles of Pto and Fen from cultivated tomato, L. esculentum, and designated them pto and fen. High conservation of genome organization between the two tomato species allowed us to identify the pto and fen alleles from among the cluster of closely related Pto gene family members. The pto and fen alleles are transcribed and have uninterrupted open reading frames that code for predicted proteins that are 87 and 98% identical to the Pto and Fen protein kinases, respectively. In vitro autophosphorylation assays revealed that both the pto and fen alleles encode active kinases. In addition, the pto kinase phosphorylates a previously characterized substrate of Pto, the Pto-interacting Pti1 serine/threonine kinase. However, the pto kinase shows impaired interaction with Pti1 and with several previously isolated Pto-interacting proteins in the yeast two-hybrid system. The observation that pto and fen are active kinases and yet do not confer bacterial speck resistance or fenthion sensitivity suggests that the amino acid substitutions distinguishing them from Pto and Fen may interfere with recognition of the corresponding signal molecule or with protein-protein interactions involved in the Pto- and Fen-mediated signal transduction pathways.
Pto基因最初源自野生番茄物种潘那利番茄（Lycopersicon pimpinellifolium），可赋予对表达无毒基因avrPto的丁香假单胞菌番茄致病变种菌株的抗性。Fen基因同样源自潘那利番茄，可赋予对杀虫剂倍硫磷的敏感性。我们现已从栽培番茄（L. esculentum）中分离并鉴定出Pto和Fen的等位基因，并将它们命名为pto和fen。两个番茄物种间基因组组织的高度保守性使我们能够从紧密相关的Pto基因家族成员簇中鉴定出pto和fen等位基因。pto和fen等位基因可转录，具有不间断的开放阅读框，编码的预测蛋白分别与Pto和Fen蛋白激酶有87%和98%的同一性。体外自磷酸化分析表明，pto和fen等位基因均编码活性激酶。此外，pto激酶可磷酸化Pto之前已鉴定的底物，即与Pto相互作用的Pti1丝氨酸/苏氨酸激酶。然而，在酵母双杂交系统中，pto激酶与Pti1以及几种之前分离出的与Pto相互作用的蛋白的相互作用受损。pto和fen是活性激酶，但却不赋予细菌性斑点病抗性或倍硫磷敏感性，这一现象表明，将它们与Pto和Fen区分开来的氨基酸替换可能会干扰对相应信号分子的识别，或干扰Pto和Fen介导的信号转导途径中涉及的蛋白质-蛋白质相互作用。
