Department of Biochemistry, Faculty of Chemistry, University of Belgrade, Belgrade, Serbia.
J Sci Food Agric. 2012 Dec;92(15):3072-8. doi: 10.1002/jsfa.5728. Epub 2012 Jun 1.
Higher plants possess several mechanisms of defense against plant pathogens. Proteins actively synthesized in response to those stresses are called defense-related proteins which, among others, include certain protease inhibitors. It is of particular relevance to investigate plant natural defense mechanisms for pathogen control which include cystatins-specific inhibitors of cysteine proteases.
In this study, a cysteine proteinase inhibitor (CPI), 11 kDa in size, was purified from green kiwifruit to homogeneity. Immuno-tissue print results indicated that CPI is most abundant in the outer layer of pericarp, near the peel, and the inner most part of the pulp-sites where it could act as a natural barrier against pathogens entering the fruit. The purified protein (15 µmol L(-1)) showed antifungal activity against two phytopathogenic fungi (Alternaria radicina and Botrytis cinerea) by inhibiting fungal spore germination. In vivo, CPI (10 µmol L(-1)) was able to prevent artificial infection of apple and carrot with spore suspension of B. cinerea and A. radicina, respectively. It also exerted activity on both intracellular and fermentation fluid proteinases.
Identification and characterization of plant defense molecules is the first step towards creation of improved methods for pathogen control based on naturally occurring molecules.
高等植物拥有多种防御植物病原体的机制。对这些胁迫作出响应而主动合成的蛋白质被称为防御相关蛋白，其中包括某些蛋白酶抑制剂。研究植物的天然防御机制以控制病原体，包括半胱氨酸蛋白酶的特异性抑制剂天冬氨酸蛋白酶抑制剂，这具有特别重要的意义。
本研究从绿猕猴桃中纯化为均一的大小为 11 kDa 的半胱氨酸蛋白酶抑制剂 (CPI)。免疫组织印迹结果表明 CPI 在果皮附近的外果皮和果肉的最内层中含量最丰富，在那里它可以作为天然屏障，防止病原体进入果实。纯化的蛋白质（15 µmol L(-1)）对两种植物病原菌（Alternaria radicina 和 Botrytis cinerea）表现出抗真菌活性，通过抑制真菌孢子萌发。在体内，CPI（10 µmol L(-1)）能够分别防止 B. cinerea 和 A. radicina 的孢子悬浮液对苹果和胡萝卜的人工感染。它还对细胞内和发酵液蛋白酶具有活性。
鉴定和表征植物防御分子是基于天然存在的分子创造改进的病原体控制方法的第一步。
