Broad spectrum of Potato Aspartic Proteinases (StAPs) cytotoxic activity against

MENDIETA, JULIETA R., DALEO, GUSTAVO R., GUEVARA, MARÍA G.

Mar del Plata

Congreso; Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2007

 Plant aspartic proteinases (EC 3.4.23) (APs) have been involved in the plant defense response. We have previously reported the purification of two potato APs (StAP1 and StAP3) that are induced by abiotic and biotic stresses and have antimicrobial activity towards the fungus F. solani and the oomycete P. infestans. The aim of this work was to characterize those antimicrobial activities and to determine the antimicrobial activity of StAPs towards others potato pathogens: the actinomycete Streptomyces scabies and the bacterium Erwinia carotovora. The results indicate that both StAPs are able to reduce the growth of S. scabies and E. carotovora cultures in a dose-dependent manner. Besides, StAPs have a potent cytotoxic activity and the lethal doses necessary to reduce the viability by 50 % (IC50) are: 2.5 µM StAP1 and 7.75 µM StAP3 for F. solani, 5 nM StAP1 and 370 nM StAP3 for P. infestans, 1.5 µM StAP1 and 1.2 µM StAP3 for S. scabies, 3.7 µM StAP1 and 3.75 µM StAP3 for E. carotovora. Assays with FITC-labelled StAPs show that proteins interact directly with the surface of pathogens. Additionally, StAPs produce in all microorganisms assayed, the generation of ROS and cellular death. The results obtained here demonstrate the broad spectrum of StAP1 and StAP3 cytotoxic activity in vitro against four different potato pathogens, suggesting their potential role in plant potato protection.