Characterization of xac4136 gene as a putative Type VI Secretion System effector in Xanthomonas citri

• Grant number: 23/05679-3
• Support Opportunities: Scholarships in Brazil - Master
• Start date: November 01, 2023
• End date: July 31, 2025
• Field of knowledge: Biological Sciences - Genetics - Molecular Genetics and Genetics of Microorganisms
• Principal Investigator: Cristina Elisa Alvarez Martinez
• Grantee: Enzo Breviglieri Sichi de Mello
• Host Institution: Instituto de Biologia (IB). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated research grant: 21/10577-0 - Biology of Bacteria and Bacteriophages Research Center, AP.CEPID

Abstract

Xanthomonas citri is a phytopathogenic gram-negative bacterium that infects citrus plants, causing significant losses to crop production in Brazil. Predation of bacteria by amoeba on the leaf surface can reduce the chances of plant infection and dissemination of phytopathogens in the environment. X. citri has a type VI secretion system (T6SS) that transports effector proteins necessary for a resistance phenotype against the soil amoeba Dictyostelium discoideum. In general, the structural components of the T6SS are co-expressed with the effector proteins it secretes, which can be toxic to eukaryotes, prokaryotes, or both. Through the study of the X. citri T6SS gene cluster, four genes encoding possible effectors were identified. Prediction of conserved domains in the protein encoded by one of these genes, xac4136, indicates the presence of characteristic eukaryotic protein motifs, a common feature of secretion system effector proteins. Moreover, overexpression of this gene in X. citri under the control of an arabinose-induced promoter resulted in growth inhibition. This work aims to characterize the protein encoded by the xac4136 gene as a T6SS effector protein through the evaluation of its toxicity and localization pattern during heterologous expression in Saccharomyces cerevisiae.