PROTEIN-KINASE-C AS A BIOMARKER FOR ASSESSING THE EFFECT OF ENVIRONMENTAL-STRESS AND FUNGAL INVASION ON PLANT DEFENSE-MECHANISM

Plants are known to activate specific defense mechanisms in response t o invasion by pathogens and environmental stresses. We examined the po ssibility of utilizing the changes in the amounts of protein kinase C (PKC) and its associated components of this signal transduction pathwa y as a biomarker of exposure of plants to the stress factors, using yo ung rice plants as a model and a Western blotting method as the experi mental tool. Preliminary studies have shown that PKC is a consistently more sensitive marker of exposure to a variety of environmental stres s factors as compared to phospholipase C (PLC) or G-protein. The titer of PKC increased as a result of exposure to herbicides, low concentra tions of copper, fungicides and other chemicals. The same trend was ob served when rice plants were stressed by severe physical treatment suc h as broken stems, deprivation of sunlight and transplantation. On the other hand, PKC levels decreased upon exposure to high winds and high concentration of copper. The most drastic rise in PKC was observed wh en rice plants were inoculated with the rice blast fungus Pyricularia oryzae. As expected, several plant protectants against the fungal inva sion also induce a rise in PKC.