Defensive Role of Plant Protease Inhibitors against Phytopathogens pp. 229-236
Authors: (V.I. Domash, M.S. Muntian, Natl. Academy of Sciences of Belarus)
Abstract: Although research on protein protease inhibitors‘ properties, their primary and spatial structure has been quite successful, data on their physiological role is still being obtained. Our results confirm the defensive role of plant protein proteinase inhibitors against phytopathogens. Proteolytic enzymes provide pathogens with peptides and amino acids derived from host plants, and destroy a plant‘s cell wall. Research establishes that synthesis of pathogens‘ extracellular proteinases of the fungi of Fusarium and Colletotrichum genus depends on special conditions such as medium composition, pH, cultivation temperature and time of cultivation. The maximum of proteolytic activity toward the following substrates: casein, azocasein and N-α-benzoyl-L-Arg-p-nitroanilide was registered after growth for 20 days at 23–25°C at pH 7–8. We derived a complex of proteinase inhibitors from potato juice and soybeans using chromatography methods. Those complexes of proteinase inhibitors at a concentration of 0.05–0.1% of active compounds led to inhibition of extracellular proteinases on 60-80 % and of mycelium growth on 80%. The way to employ those proteins as a new generation of environmental friendly fungicides is now in progress. It is a well known fact that a common property of PR (pathogenesis related proteins) is their ability to get through seed cover into the medium where seeds are grown. And we have found that trypsin, chymotrypsin and subtilisin inhibitors are also able to diffuse through the cover of Fabaceae family seeds into water where they germinate. The molecular mass of those proteins determined by PAAG electrophoresis was in the range 14–45 kDa. The solution consisting of proteinase inhibitors (diffusate) causes the suppression of pathogens spore germination and hyphae growth on 45–82%, which may confirm a possible defensive role of protein inhibitors on early stages of seed germination.