Citriculture, an important economic activity in Brazil, is threatened by diseases that attack crops, such as citrus canker produced by Xanthomonas citri, which leads to reduced productivity and significant economic losses. Bacterial sigma factors are dissociable subunits of RNA polymerases that are responsible for the recognition of promoters and for promoting the initiation of transcription. Among them, the family of sigma extracyplasmic factors (ECF), regulates gene expression in response to signals detected in the bacterial cell envelope. The functional characterization of sigma factor EcfL of X. citri allowed us to demonstrate its role in virulence and growth under conditions of phosphate deficiency. In addition, transcriptome analysis of a strain with increased levels of ecfL led to the identification of the regulon of this ECF factor, which is composed of 3 genes, located in the vicinity of ecfL in the genome of X. citri. Curiously, ecfL and genes from its regulon are located in a gene cluster that encodes a type 6 protein secretion system (SS6) involved in the resistance of X.citri to predation by amoeba Distyostelium discoideum. The in silico analysis of the proteins encoded by the genes of EcfL regulon reveals the presence of interesting functional domains, which allow us to make predictions about the function of these proteins. Thus, this project aims to perform the biochemical and functional characterization of two proteins that are part of the regulon of EcfL. This study will allow a better understanding of the role of EcfL in the physiology of X. citri and may lead to the identification of new functions important to the virulence of this bacterium and/or to resistance to predation by environmental amoebae.
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