Zhou N, Tootle T L, Tsui F, Klessig D F, Glazebrook J
Center for Agricultural Biotechnology, University of Maryland Biotechnology Institute, College Park, Maryland 20742, USA.
Plant Cell. 1998 Jun;10(6):1021-30. doi: 10.1105/tpc.10.6.1021.
The Arabidopsis PAD4 gene was previously shown to be required for synthesis of camalexin in response to infection by the virulent bacterial pathogen Pseudomonas syringae pv maculicola ES4326 but not in response to challenge by the non-host fungal pathogen Cochliobolus carbonum. In this study, we show that pad4 mutants exhibit defects in defense responses, including camalexin synthesis and pathogenesis-related PR-1 gene expression, when infected by P. s. maculicola ES4 326. No such defects were observed in response to infection by an isogenic avirulent strain carrying the avirulence gene avrRpt2. In P. s. maculicola ES4 326-infected pad4 plants, synthesis of salicylic acid (SA) was found to be reduced and delayed when compared with SA synthesis in wild-type plants. Moreover, treatment of pad4 plants with SA partially reversed the camalexin deficiency and PR-1 gene expression phenotypes of P. s. maculicola ES4 326-infected pad4 plants. These findings support the hypothesis that PAD4 acts upstream from SA accumulation in regulating defense response expression in plants infected with P. s. maculicola ES4 326. A working model of the role of PAD4 in governing expression of defense responses is presented.
拟南芥PAD4基因先前已被证明在响应毒性细菌病原体丁香假单胞菌番茄致病变种ES4326感染时，对于合成植保素至关重要，但在响应非寄主真菌病原体玉米小斑病菌的攻击时并非如此。在本研究中，我们表明，当被丁香假单胞菌番茄致病变种ES4326感染时，pad4突变体在防御反应中表现出缺陷，包括植保素合成和病程相关PR-1基因表达。在被携带无毒基因avrRpt2的同基因无毒菌株感染时，未观察到此类缺陷。在被丁香假单胞菌番茄致病变种ES4326感染的pad4植株中，与野生型植株中的水杨酸（SA）合成相比，发现SA合成减少且延迟。此外，用SA处理pad4植株部分逆转了被丁香假单胞菌番茄致病变种ES4326感染的pad4植株的植保素缺乏和PR-1基因表达表型。这些发现支持了以下假设：在调控被丁香假单胞菌番茄致病变种ES4326感染的植物中的防御反应表达时，PAD4在SA积累的上游起作用。本文提出了PAD4在调控防御反应表达中的作用的工作模型。
