Harfouche Antoine L, Rugini Eddo, Mencarelli Fabio, Botondi Rinaldo, Muleo Rosario
Dipartimento di Produzione Vegetale, Università degli Studi della Tuscia, Via S.C. de Lellis, Viterbo 01100, Italy.
J Plant Physiol. 2008 May 5;165(7):734-44. doi: 10.1016/j.jplph.2007.03.010. Epub 2007 Aug 31.
Salicylic acid (SA), ethylene (ET), and wounding are all known to influence plant defense response. Experiments attempting to determine SA's relation to ET biosynthesis and defense gene expression have shown conflicting results. To confront this, we developed an in vitro model system to investigate how SA affects ET biosynthesis, hydrogen peroxide (H(2)O(2)) production and endochitinase gene expression in the European chestnut. ET measurements of in vitro shoots indicated a critical time point for SA exogenous application, enabling us to study its effects independent of ET. In addition, ET measurements demonstrated that its own increased biosynthesis was a response to wounding but not to SA treatment. Application of the ET biosynthesis inhibitor, aminoethoxyvinylglycine (AVG), on wounded and SA-treated shoots blocked wounding-induced ET production. Interestingly, SA inhibited ET production, but to a lesser extent than AVG. Additionally, SA also induced the accumulation of endochitinase transcript level. Likewise, a sensitive tissue-print assay showed that SA further increased the level of H(2)O(2). Yet, SA-induced endochitinase gene expression and SA-enhanced H(2)O(2) production levels were independent of ET. The cumulative results indicate that SA acts as an inducer of endochitinase PR gene expression and of H(2)O(2) oxidative burst. This suggests that SA is a component of the signal transduction pathway leading to defense against pathogens in chestnut. Further, the model system developed for this experiment should facilitate the deciphering of defense signaling pathways and their cross-talk. Moreover, it should also benefit the study of trees of long generation time that are known to be recalcitrant to in vitro studies.
水杨酸（SA）、乙烯（ET）和机械损伤均已知会影响植物的防御反应。旨在确定SA与ET生物合成及防御基因表达之间关系的实验结果相互矛盾。为解决这一问题，我们开发了一个体外模型系统，以研究SA如何影响欧洲栗中ET的生物合成、过氧化氢（H₂O₂）的产生及内切几丁质酶基因的表达。对体外培养枝条的ET测量表明了SA外源施用的关键时间点，使我们能够独立于ET研究其作用效果。此外，ET测量显示其自身生物合成的增加是对机械损伤的反应，而非SA处理的反应。在受伤和经SA处理的枝条上施用ET生物合成抑制剂氨基乙氧基乙烯基甘氨酸（AVG），可阻断机械损伤诱导的ET产生。有趣的是，SA抑制ET的产生，但程度小于AVG。此外，SA还诱导了内切几丁质酶转录水平的积累。同样，一种灵敏的组织印迹分析表明，SA进一步提高了H₂O₂的水平。然而，SA诱导的内切几丁质酶基因表达及SA增强的H₂O₂产生水平均独立于ET。累积结果表明，SA作为内切几丁质酶PR基因表达及H₂O₂氧化爆发的诱导剂。这表明SA是导致栗树对病原体防御的信号转导途径的一个组成部分。此外，为本实验开发的模型系统应有助于破解防御信号通路及其相互作用。而且，它也应有利于对已知难以进行体外研究的长世代树木的研究。
