Laboratory of Plant Molecular Biology and Biotechnology, Faculty of Sciences, Department of Life Sciences, University of Liège, Boulevard du Rectorat, 27, Liège, Belgium.
BMC Plant Biol. 2011 Feb 4;11:29. doi: 10.1186/1471-2229-11-29.
Some non-pathogenic rhizobacteria called Plant Growth Promoting Rhizobacteria (PGPR) possess the capacity to induce in plant defense mechanisms effective against pathogens. Precedent studies showed the ability of Pseudomonas putida BTP1 to induce PGPR-mediated resistance, termed ISR (Induced Systemic Resistance), in different plant species. Despite extensive works, molecular defense mechanisms involved in ISR are less well understood that in the case of pathogen induced systemic acquired resistance.
We analyzed the activities of phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX), key enzymes of the phenylpropanoid and oxylipin pathways respectively, in tomato treated or not with P. putida BTP1. The bacterial treatment did not stimulate PAL activity and linoleate-consuming LOX activities. Linolenate-consuming LOX activity, on the contrary, was significantly stimulated in P. putida BTP1-inoculated plants before and two days after infection by B. cinerea. This stimulation is due to the increase of transcription level of two isoforms of LOX: TomLoxD and TomLoxF, a newly identified LOX gene. We showed that recombinant TomLOXF preferentially consumes linolenic acid and produces 13-derivative of fatty acids. After challenging with B. cinerea, the increase of transcription of these two LOX genes and higher linolenic acid-consuming LOX activity were associated with a more rapid accumulation of free 13-hydroperoxy-octadecatrienoic and 13-hydroxy-octadecatrienoic acids, two antifungal oxylipins, in bacterized plants.
In addition to the discovery of a new LOX gene in tomato, this work is the first to show differential induction of LOX isozymes and a more rapid accumulation of 13-hydroperoxy-octadecatrienoic and 13-hydroxy-octadecatrienoic acids in rhizobacteria mediated-induced systemic resistance.
一些非致病性根际细菌被称为植物生长促进根际细菌（PGPR），它们具有诱导植物防御机制对抗病原体的能力。先前的研究表明，假单胞菌 BTP1 能够诱导 PGPR 介导的抗性，称为 ISR（诱导系统抗性），在不同的植物物种中。尽管进行了广泛的研究，但 ISR 涉及的分子防御机制还不如对病原体诱导的系统获得性抗性的了解。
我们分析了苯丙氨酸解氨酶（PAL）和脂氧合酶（LOX）的活性，分别是苯丙烷和氧化脂途径的关键酶，在经过或未经 P. putida BTP1 处理的番茄中。细菌处理并没有刺激 PAL 活性和消耗亚油酸的 LOX 活性。相反，在 B. cinerea 感染前和感染后两天，接种 P. putida BTP1 的植物中，消耗亚麻酸的 LOX 活性显著增加。这种刺激是由于两种 LOX 同工型 TomLoxD 和 TomLoxF 的转录水平增加所致，TomLoxF 是一种新鉴定的 LOX 基因。我们表明，重组 TomLOXF 优先消耗亚麻酸并产生 13-脂肪酸衍生物。在受到 B. cinerea 挑战后，这两个 LOX 基因的转录增加和消耗更多亚麻酸的 LOX 活性与在细菌化植物中更快地积累游离 13-羟基-十八碳三烯酸和 13-羟基-十八碳三烯酸有关，这两种是抗真菌的氧化脂素。
除了在番茄中发现一种新的 LOX 基因外，这项工作首次表明，LOX 同工型的差异诱导和在根际细菌介导的诱导系统抗性中更快地积累 13-羟基-十八碳三烯酸和 13-羟基-十八碳三烯酸。
