Rose Laura E, Langley Charles H, Bernal Adriana J, Michelmore Richard W
Center for Population Biology, University of California, Davis, California 95616, USA.
Genetics. 2005 Sep;171(1):345-57. doi: 10.1534/genetics.104.039339. Epub 2005 Jun 8.
Disease resistance to the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) in the cultivated tomato, Lycopersicon esculentum, and the closely related L. pimpinellifolium is triggered by the physical interaction between plant disease resistance protein, Pto, and the pathogen avirulence protein, AvrPto. To investigate the extent to which variation in the Pto gene is responsible for naturally occurring variation in resistance to Pst, we determined the resistance phenotype of 51 accessions from seven species of Lycopersicon to isogenic strains of Pst differing in the presence of avrPto. One-third of the plants displayed resistance specifically when the pathogen expressed AvrPto, consistent with a gene-for-gene interaction. To test whether this resistance in these species was conferred specifically by the Pto gene, alleles of Pto were amplified and sequenced from 49 individuals and a subset (16) of these alleles was tested in planta using Agrobacterium-mediated transient assays. Eleven alleles conferred a hypersensitive resistance response (HR) in the presence of AvrPto, while 5 did not. Ten amino acid substitutions associated with the absence of AvrPto recognition and HR were identified, none of which had been identified in previous structure-function studies. Additionally, 3 alleles encoding putative pseudogenes of Pto were isolated from two species of Lycopersicon. Therefore, a large proportion, but not all, of the natural variation in the reaction to strains of Pst expressing AvrPto can be attributed to sequence variation in the Pto gene.
栽培番茄（Lycopersicon esculentum）及其近缘种潘那利番茄（L. pimpinellifolium）对细菌性病原菌丁香假单胞菌番茄致病变种（Pseudomonas syringae pv. tomato，Pst）的抗病性，是由植物抗病蛋白Pto与病原菌无毒蛋白AvrPto之间的物理相互作用触发的。为了研究Pto基因变异在多大程度上导致了对Pst抗性的自然变异，我们测定了来自番茄属七个物种的51份材料对含有不同avrPto的Pst同基因菌株的抗性表型。三分之一的植株仅在病原菌表达AvrPto时表现出抗性，这与基因对基因的相互作用一致。为了测试这些物种中的这种抗性是否由Pto基因特异性赋予，从49个个体中扩增并测序了Pto的等位基因，并使用农杆菌介导的瞬时试验在植物中测试了其中一个子集（16个）的等位基因。11个等位基因在存在AvrPto时产生超敏抗性反应（HR），而5个则没有。鉴定出了10个与缺乏AvrPto识别和HR相关的氨基酸取代，在以前的结构功能研究中均未发现。此外，从番茄属的两个物种中分离出3个编码Pto假定假基因的等位基因。因此，对表达AvrPto的Pst菌株反应的大部分（但不是全部）自然变异可归因于Pto基因的序列变异。
