水稻纹枯病菌胞外蛋白酶特性研究

Characterization of an extra-cellular protease produced by Rhizoctonia solani

植物病原菌产生蛋白水解酶被认为是病原菌侵染寄主的一个重要策略。作者对水稻纹枯病菌(Rhizoctonia solani Kühn)产生的胞外蛋白酶的特性进行了研究。结果表明,水稻纹枯病菌产生一个分子量约为49.5ku的胞外蛋白酶。该酶对胰蛋白酶专一性底物Benz-Phe-Val-Arg-NA有较高的活性,并能从羧基端降解Arg和Lys。胰蛋白酶抑制剂对该酶活性有较强的抑制作用,表明该蛋白酶是一种类胰蛋白酶。在离体试验下,该蛋白酶可以降解水稻细胞壁蛋白并释放羟脯氨酸。SDS-PAGE电泳分析显示,至少有4个多肽被降解,分子量范围分别在14.4～20.1、20.1～31ku和31～43ku范围内。说明该胞外蛋白酶具有降解水稻细胞壁的能力,因此,该蛋白酶可能在水稻纹枯病菌的致病过程中起重要作用。

Proteolytic enzymes have been proposed as one of the invasion strategies for plant pathogens. In this study, an extra-cellular protease from Rhizoctonia solani was studied. The enzyme has a molecular mass of 49.5 ku based on SDS-PAGE. It showed high proteolytic activity against the trypsin substrate Benz-Phe-Val-Arg-NA and cleaved peptide bonds on the carboxyl side of lysine or arginine. Its activity was strongly inhibited by the trypsin inhibitors. It was able to degrade cell wall proteins from rice, releasing hydroxyproline. Degradation of at least four polypeptides of 14.4--20.1 ku, 20.1--31 ku and 31--43 ku was detected by SDS-PAGE. The result suggests that the protease might play an important role in the pathogenicity of R. solani to rice.