Meier B M, Shaw N, Slusarenko A J
Institut für Pflanzenbiologie, Zürich, Switzerland.
Mol Plant Microbe Interact. 1993 Jul-Aug;6(4):453-66. doi: 10.1094/mpmi-6-453.
Primary leaves of 7- to 9-day-old Red Mexican bean plants were inoculated with virulent or avirulent isolates of Pseudomonas syringae pv. phaseolicola, or saprophytic P. fluorescens either by vacuum infiltration of the whole leaf lamina, or by syringe-inoculation of selected leaf panels. In the incompatible combination, resistance was associated with a hypersensitive response (HR). Syringe-inoculated leaves were sampled in three zones: zone 1, the inoculated leaf area; zone 2, the surrounding 0.5-0.7 cm of leaf tissue; and zone 3, the remainder of the leaf. Northern blots of RNA from zones 1, 2, and 3 were probed with bean cDNAs for phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chitinase (CHT), and lipoxygenase (LOX). Accumulation of PAL, CHS, and CHT transcripts was more rapid and generally of greater magnitude in the incompatible than in the compatible interaction and, in both cases, was observed essentially only in zone 1 tissues. Similarly, antibacterial phytoalexins were only detected in zone 1 from the incompatible interaction. Young primary leaves have a background level of LOX transcripts, which declines as leaves age. This decline was accelerated over the first 12 hr postinoculation (hpi) with avirulent bacteria, whereas a weak transient induction, peaking at 5-6 hpi, was observed in the compatible interaction. A subsequent, strong accumulation of LOX transcripts was seen in both the compatible and incompatible interactions outside the inoculation site starting about 14 hpi. LOX transcripts did not accumulate at the inoculation site itself in the incompatible interaction compared to a relatively strong induction in the compatible interaction. Interestingly, inoculation of leaves with cells of the saprophyte P. fluorescens also induced the accumulation of transcripts for CHS, CHT, and LOX, but generally to a lesser degree than in the incompatible interaction. No HR occurred and no macroscopic cell damage was apparent in leaves inoculated with P. fluorescens. However, at the microscopic level individual, trypan blue-stained, necrotic plant cells were visible. In spite of this and the accumulation of CHS transcripts, no phytoalexin accumulation was found up to 48 hr after inoculation. The spatial and temporal relationship of the hypersensitive reaction to defense gene transcript and phytoalexin accumulation is discussed.
通过对整个叶片进行真空渗透或对选定的叶面板进行注射器接种，将毒性或无毒的菜豆假单胞菌菌株，或腐生荧光假单胞菌接种到7至9日龄的红色墨西哥豆植株的初生叶上。在不亲和组合中，抗性与过敏反应（HR）相关。对用注射器接种的叶片在三个区域取样：区域1，接种的叶面积；区域2，周围0.5 - 0.7厘米的叶组织；区域3，叶片的其余部分。用豆类苯丙氨酸解氨酶（PAL）、查尔酮合酶（CHS）、几丁质酶（CHT）和脂氧合酶（LOX）的cDNA对来自区域1、2和3的RNA进行Northern杂交。在不亲和相互作用中，PAL、CHS和CHT转录本的积累比在亲和相互作用中更快，且通常幅度更大，并且在两种情况下，基本上仅在区域1组织中观察到。同样，抗菌植物抗毒素仅在不亲和相互作用的区域1中检测到。幼嫩的初生叶具有LOX转录本的背景水平，随着叶片变老该水平下降。接种无毒细菌后，在接种后最初12小时（hpi）内这种下降加速，而在亲和相互作用中观察到在5 - 6 hpi达到峰值的微弱短暂诱导。在接种后约14 hpi开始，在接种部位之外的亲和与不亲和相互作用中均观察到LOX转录本随后的强烈积累。与亲和相互作用中相对强烈的诱导相比，在不亲和相互作用中接种部位本身没有LOX转录本的积累。有趣的是，用腐生荧光假单胞菌的细胞接种叶片也诱导了CHS、CHT和LOX转录本的积累，但通常程度低于不亲和相互作用。接种荧光假单胞菌的叶片中未发生HR，也没有明显的宏观细胞损伤。然而，在微观水平上可见单个经台盼蓝染色的坏死植物细胞。尽管如此以及有CHS转录本的积累，但在接种后48小时内未发现植物抗毒素的积累。本文讨论了过敏反应与防御基因转录本和植物抗毒素积累之间的时空关系。
