Study of the role of a harpin from Xanthomonas axonopodis pv. citri in citrus canker

SGRO GG; DUNGER G; ORELLANO EG; GOTTIG N; OTTADO J

Puerto Madryn, Chubut, Argentina

Congreso; XLVI Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2010

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Phytopathogenic bacteria colonize their hosts through the secretion of effector proteins by using the Type III Secretion System. This system is encoded by the hrp cluster (hypersensitive response (HR) and pathogenicity), which is essential for pathogenicity in host plants and induction of HR in non-host plants since it mediates the translocation of effector proteins to the plant cell. HR is characterized by a local rapid programmed cell death that is induced after recognition of the pathogen and slows the spread of infection. The hrp cluster of Xanthomonas axonopodis pv. citri (Xac) contains a gene that codes for a harpin protein called Hpa1. Harpins are glycine-rich heat stable proteins that can form pores in membranes and can induce HR in some plants. In order to study the functionality of Hpa1 protein from Xac, it was expressed and purified in a recombinant form. We observed that Hpa1 produces HR in tobacco and pepper plants. To study the effect of Hpa1 during the disease we constructed a Xac ∆hpa1 mutant by marker exchange. Infiltration of this mutant caused less number of cankers relative to the wild type bacteria. Moreover, co/infiltrations of Xac WT with the recombinant protein also produced a greater number of cankers in the presence of the protein. These results indicate that Hpa1 is involved in the elicitation of HR in non-host plants as well as in virulence in host plants.