Study of novel functions of Xanthomonas citri subsp. citri hrp cluster

CRESPO R; GARAVAGLIA BS; OTTADO J; GOTTIG N

Rosario

Congreso; L Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular.; 2014

SAIB

Xanthomonas citri subsp. citri (X. citri), the bacterium responsible for citrus canker possesses a hrp gene cluster involved in hypersensitive response and pathogenicity. This hrp cluster encodes the type three protein secretion system (T3SS). We have demonstrated that X. citri T3SS, besides its participation in the secretion and translocation of effector proteins into the host cell, is also required for biofilm formation, motility and survival on leaf tissue revealing novel functions for this system. A proteomic analysis was performed to identify differentially expressed proteins between X. citri and a mutant in the hrp cluster (hrpB−) grown statically. Most of the identified proteins belong to different classes of outer membrane proteins, suggesting that the lack of the T3SS impairs membrane stability. To test this, in this work we evaluated the survival capacity of X. citri, the hrpB− mutant and the hrpB−c complemented strain under the presence of membrane destabilizing agents, such as SDS. The resistance to salt and oxidative stress of these strains was also assayed. X. citri and hrpB−c showed a higher tolerance to these treatments than the hrpB− mutant. Moreover, qRT-PCR assays showed that the expression of the hrp cluster is induced upon stress conditions. Our results reinforce the hypothesis that T3SS stabilized X. citri membranes.