FUNGAL PROTEASE INDUCES A DEFENSE RESPONSE IN PLANTS

CHALFOUN, NADIA REGINA; CASTAGANARO, ATILIO P; DÍAZ RICCI, JUAN C.

Salta

Congreso; 42 Congreso Argentino de Genética; 2013

Sociedad Argentina de Genética

Phytopathogenic fungi can secrete hydrolytic enzymes to degrade and traverse the outer structural barriers of plant tissues. Among them subtilisin-like proteinases are considered important virulence factors in the infection process We have isolated and purified a protein called AsES, secreted by the fungus Acremonium strictum that induces a strong defensive response against the pathogen Colletotrichum, the etiological agent of the anthracnose disease in strawberry. BLAST analysis yielded significant similarity with serine proteases of the subfamily of proteinase K-like subtilisins (S8A) and 65% of identical amino acids sequences with a proteinase T-like subtilisin from the saprophyte Trichoderma reesei. The protein AsES also showed similarity with the other serine proteases identified in Acremonium spp., but none of them exhibits biological activity in plants or in other organisms. AsES exhibited proteolytic activity in vitro and its resistance-eliciting activity was eliminated when inhibited with PMSF, suggesting that its proteolytic activity is required to induce the defense response. To our knowledge, this is the first report of a fungal subtilisin that shows defense-eliciting activity in plants. Since the elicitor activity was only found in AsES from SS71 A. strictum and not was found in a homologous subtilisin as proteinase K, we conclude that the proteolytic activity is necessary but not sufficient to induce defense and suggest that AsES might induce defense by means of proteolysis of one or multiple host proteins that are specific targets of this protease.