Rotblat Barak, Enshell-Seijffers David, Gershoni Jonathan M, Schuster Silvia, Avni Adi
Department of Plant Sciences, Faculty of Life Sciences Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel.
Plant J. 2002 Dec;32(6):1049-55. doi: 10.1046/j.1365-313x.2002.01490.x.
Defense mechanisms of plants against pathogens often entail cell wall strengthening, ethylene biosynthesis, expression of pathogen-related proteins and hypersensitive responses (HR). Pathogen-derived elicitors trigger these defense responses. The Elicitor Ethylene-inducing Xylanase (EIX) elicits HR and other plant defense responses in some tobacco and tomato cultivars independently of its xylan degradation activity. The elicitation epitope on the EIX protein responsible for inducing the HR response has been elucidated. Through the generation of EIX-specific polyclonal antibodies and screening of combinatorial phage display peptide libraries an essential sequence of the EIX elicitation activity has been identified. This sequence consists of the pentapeptide TKLGE mapped to an exposed beta-strand of the EIX protein. Substitution of the pentapeptide TKLGE to VKGT inhibited the elicitation activity but not the beta-1-4-endoxylanase activity of the EIX protein further demonstrating that elicitation and enzyme activity are independent properties. Elucidation of a peptide sequence that is essential for elicitation of HR creates the opportunity to understand the control and signaling of plant defense.
植物对抗病原体的防御机制通常包括细胞壁强化、乙烯生物合成、病程相关蛋白的表达以及过敏反应（HR）。病原体衍生的激发子会触发这些防御反应。激发子诱导乙烯产生的木聚糖酶（EIX）在一些烟草和番茄品种中引发过敏反应和其他植物防御反应，与其木聚糖降解活性无关。已阐明EIX蛋白上负责诱导过敏反应的激发表位。通过产生EIX特异性多克隆抗体并筛选组合噬菌体展示肽库，已鉴定出EIX激发活性的一个必需序列。该序列由定位到EIX蛋白暴露β链上的五肽TKLGE组成。将五肽TKLGE替换为VKGT可抑制EIX蛋白的激发活性，但不影响其β-1,4-内切木聚糖酶活性，进一步证明激发和酶活性是独立的特性。阐明对引发过敏反应至关重要的肽序列为理解植物防御的调控和信号传导创造了机会。
