PLANT SPECIFIC INSERT (PSI) OF StAPs: CLONING, EXPRESSION AND ANTIMICROBIAL ACTIVITY.

MUÑOZ, FERNANDO F.; MENDIETA, JULIETA R.; PAGANO, MARIANA R.; DALEO GUSTAVO R.; GUEVARA MARÍA G.

Rosario, Santa Fe, Argentina

Congreso; Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2006

Precursors of Plant Aspartic Proteasas have in their amino acid sequence a domain named “Plant Specific Insert” (PSI). This domain has structural homology with saposin-like proteins, a family of proteins with capacity to destabilize microbial plasma membrane. We have previously reported that Potato Aspartic Proteases (StAPs), have PSI domain into mature proteins with capacity to permeabilize pathogens plasma membranes. In order to study the possible role of PSI in the antimicrobial activity of StAPs, the aim of this work was clone the PSI domain, express it in a heterologue system and analyse its antifungal activity. Viability assays demonstrated that recombinant PSI (StAP-PSIr) is able to kill spores of F. solani in a dose-dependent manner. Besides, localization experiments with FITC-labelled StAP-PSIr showed a direct interaction with the surface of spores and hyphae of F. solani. Moreover, incubation of spores and hyphae with StAP-PSIr resulted in membrane permeabilization as was shown by the uptake of the probe SYTOX Green. In conclusion, we were able to obtain the recombinant PSI and tested its antifungal activity towards F. solani. Therefore, these results could suggest this domain plays an essential role in the antimicrobial activity previously reported for StAPs.