Antimicrobial activity of StAPs (Solanum tuberosum aspartic proteinases) involves membrane permeabilization of target cells

M. PAGANO, UNIV. NACL DE MAR DEL PLATA; G. DALEO, UNIV. NACL DE MAR DEL PLATA; M. GUEVARA, UNIV. NACL DE MAR DEL PLATA

Austin, Texas, EEUU

Congreso; Annual meeting of The American Phytopathological Society; 2005

Biological functions of plant aspartic proteinases (APs) are not as well assigned or characterized as those of their mammalian, microbial or viral counterparts. We have previously reported the purification of two potato APs (StAPs) with antimicrobial activity towards plant pathogens. The aim of this work was to determine if the antimicrobial activity of StAPs involves a cytotoxic effect and changes in the fungal membrane permeabilization. The assays to measure the antimicrobial activity previously reported to these APs did not allow us to determine if StAPs affect the viability of F. solani. Results obtained show that both StAPs were able to reduce the viability of spores in a dose and time dependent manner. The presence of StAPs produces the generation of oxygen reactive species (ROS) and the uptake of the fluorogenic dye SYTOX Green; this probe only penetrates cells that have compromised plasma membranes. These evidences and the previously obtained results that show a direct interaction between StAPs and spores indicate that antimicrobial activity of StAPs involves a direct cytotoxic effect and alterations in fungal membrane permeability. However although, the exact mechanism of action of StAPs has not yet been solved, the results reported here indicate a plasma membrane-based action of StAPs.