Alfalfa snakin-1 prevents fungal colonization and probably coevolved with rhizobia

Background: The production of antimicrobial peptides is a common defense strategy of living cells against a wide range of pathogens. Plant snakin peptides inhibit bacterial and fungal growth at extremely low concentrations. However, little is known of their molecular and ecological characteristics, including origin, evolutionary equivalence, specific functions and activity against beneficial microbes. The aim of this study was to identify and characterize snakin-1 from alfalfa (MsSN1). Results: Phylogenetic analysis showed complete congruence between snakin-1 and plant trees. The antimicrobial activity of MsSN1 against bacterial and fungal pathogens of alfalfa was demonstrated in vitro and in vivo. Transgenic alfalfa overexpressing MsSN1 showed increased antimicrobial activity against virulent fungal strains. However, MsSN1 did not affect nitrogen-fixing bacterial strains only when these had an alfalfa origin. Conclusions: The results reported here suggest that snakin peptides have important and ancestral roles in land plant innate immunity. Our data indicate a coevolutionary process, in which alfalfa exerts a selection pressure for resistance to MsSN1 on rhizobial bacteria. The increased antimicrobial activity against virulent fungal strains without altering the nitrogen-fixing symbiosis observed in MsSN1-overexpressing alfalfa transgenic plants opens the way to the production of effective legume transgenic cultivars for biotic stress resistance.

Instituto de Genética

Fil: Garcia, Araceli Nora. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina

Fil: Ayub, Nicolás Daniel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina

Fil: Fox, Ana Romina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina.

Fil: Gomez, Maria Cristina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina

Fil: Dieguez, María José. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina

Fil: Pagano, Elba Maria. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina

Fil: Berini, Carolina Andrea. Instituto de Investigaciones Biomédicas en Retrovirus y SIDA; Argentina

Fil: Muschietti, Jorge Prometeo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, “Dr. Hector Torres”; Argentina

Fil: Soto, Gabriela Cinthia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina