Smith-Becker J, Marois E, Huguet E J, Midland S L, Sims J J, Keen N T
Department of Plant Pathology, University of California, Riverside 92521, USA.
Plant Physiol. 1998 Jan;116(1):231-8. doi: 10.1104/pp.116.1.231.
Cucumber (Cucumis sativa) leaves infiltrated with Pseudomonas syringae pv. syringae cells produced a mobile signal for systemic acquired resistance between 3 and 6 h after inoculation. The production of a mobile signal by inoculated leaves was followed by a transient increase in phenylalanine ammonia-lyase (PAL) activity in the petioles of inoculated leaves and in stems above inoculated leaves; with peaks in activity at 9 and 12 h, respectively, after inoculation. In contrast, PAL activity in inoculated leaves continued to rise slowly for at least 18 h. No increases in PAL activity were detected in healthy leaves of inoculated plants. Two benzoic acid derivatives, salicylic acid (SA) and 4-hydroxybenzoic acid (4HBA), began to accumulate in phloem fluids at about the time PAL activity began to increase, reaching maximum concentrations 15 h after inoculation. The accumulation of SA and 4HBA in phloem fluids was unaffected by the removal of all leaves 6 h after inoculation, and seedlings excised from roots prior to inoculation still accumulated high levels of SA and 4HBA. These results suggest that SA and 4HBA are synthesized de novo in stems and petioles in response to a mobile signal from the inoculated leaf.
用丁香假单胞菌丁香致病变种（Pseudomonas syringae pv. syringae）细胞浸润黄瓜（Cucumis sativa）叶片后，接种后3至6小时产生了一种用于系统获得性抗性的移动信号。接种叶片产生移动信号后，接种叶片叶柄和接种叶片上方茎中的苯丙氨酸解氨酶（PAL）活性短暂增加；接种后分别在9小时和12小时达到活性峰值。相比之下，接种叶片中的PAL活性至少持续缓慢上升18小时。在接种植物的健康叶片中未检测到PAL活性增加。两种苯甲酸衍生物，水杨酸（SA）和4-羟基苯甲酸（4HBA），大约在PAL活性开始增加时开始在韧皮部汁液中积累，接种后15小时达到最大浓度。接种后6小时去除所有叶片，韧皮部汁液中SA和4HBA的积累不受影响，接种前从根部切除的幼苗仍积累高水平的SA和4HBA。这些结果表明，SA和4HBA是在茎和叶柄中重新合成的，以响应来自接种叶片的移动信号。
