By: KIM H. T.; YAMAGUCHI I.
Pencycuron exerts a specific inhibitory activity on Rhizoctonia solani isolates even in the same anastomosis group, AG4. The sensitivity of AG4 isolates to pencycuron was negatively correlated with the mycelial growth at high temperature (30°C). Based on such observation and high lipophilicity of pencycuron, the influence of pencycuron on the fluidity of lipid membranes of R. solani was examined. The composition ratio of saturated fatty acids such as palmitic acid and stearic acid in R-C (an isolate sensitive to pencycuron) was higher than that in Rh-131 (a far less-sensititve isolate). On the contrary, linoleic acid, an unsaturated fatty acid, was more abundant in Rh-131. While the fluidity of liposomes prepared with total lipids from R-C remarkably decreased by the application of pencycuron, no significant diminution of membrane fluidity was observed in liposomes from Rh-131. With artificial liposomes prepared from phosphatidylcholines commercially available, the membrane fluidity fluctuated depending on the composition of fatty acids, and the effect of pencycuron on the membrane fluidity was more significant in liposomes composed of higher ratio of saturated fatty acids. It was also found that 14 C-pencycuron was bound 3 times more by liposomes that resembled R-C membrane in composition of fatty acids than those mimicked the membranes of Rh-131. From the results obtained, it is suggested that the binding of pencycuron is closely related with the composition of lipid membranes, and the binding of pencycuron to the membrane causes the decrease of membrane fluidity in sensitive isolates of R. solani.
Pencycuron exerts a specific inhibitory activity on Rhizoctonia solani isolates even in the same anastomosis group, AG4. The sensitivity of AG4 isolates to pencycuron was negatively correlated with the mycelial growth at high temperature (30°C). Based on such observation and high lipophilicity of pencycuron, the influence of pencycuron on the fluidity of lipid membranes of R. solani was examined. The composition ratio of saturated fatty acids such as palmitic acid and stearic acid in R-C (an isolate sensitive to pencycuron) was higher than that in Rh-131 (a far less-sensititve isolate). On the contrary, linoleic acid, an unsaturated fatty acid, was more abundant in Rh-131. While the fluidity of liposomes prepared with total lipids from R-C remarkably decreased by the application of pencycuron, no significant diminution of membrane fluidity was observed in liposomes from Rh-131. With artificial liposomes prepared from phosphatidylcholines commercially available, the membrane fluidity fluctuated depending on the composition of fatty acids, and the effect of pencycuron on the membrane fluidity was more significant in liposomes composed of higher ratio of saturated fatty acids. It was also found that 14 C-pencycuron was bound 3 times more by liposomes that resembled R-C membrane in composition of fatty acids than those mimicked the membranes of Rh-131. From the results obtained, it is suggested that the binding of pencycuron is closely related with the composition of lipid membranes, and the binding of pencycuron to the membrane causes the decrease of membrane fluidity in sensitive isolates of R. solani.
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