Roles of the Pil-Chp signaling system in Xanthomonas citri

• Grant number: 25/09665-2
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: July 01, 2025
• End date: June 30, 2029
• Field of knowledge: Biological Sciences - Biochemistry - Biochemistry of Microorganisms
• Principal Investigator: Regina Lúcia Baldini
• Grantee: Pedro Bonato Araujo
• Host Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 21/10577-0 - Biology of Bacteria and Bacteriophages Research Center, AP.CEPID

Abstract

Organisms coordinate their functions by receiving information from the environment and using them to adjust the pathways that allow its survival and adaptation. Bacterial signaling, transduction and response systems must be finely regulated to guarantee their success in specific situations. The type IV pilus (T4P) is a cellular appendage that allows bacteria to move on surfaces by twitching, to initiate biofilm growth, to incorporate extracellular DNA by transformation and it can also be a receptor for phages. The T4P is a complex molecular machine that spans the bacterial envelope, and its activity is controlled by ATPases. The T4P was shown to act as a mechanosensor in P. aeruginosa: depolymerization of the PilA filament upon surface contact elicits a response transduced by a phosphorelay cascade, where PilJ inner membrane protein is the sensor and ChpA is the class II histidine kinase that phosphorylates two response regulators (RR), PilH and PilG. These RRs are composed of a single REC domain and perform opposite roles in regulating the adenylate cyclase CyaA. Activation of CyaA increases the cAMP levels, allowing a CRP-like transcriptional activator to bind to promoters of virulence-related genes. This Pil-Chp regulatory system is composed by other accessory proteins and the genes are encoded in chromosomal adjacent clusters conserved among several bacteria, including Xanthomonas citri. However, there is no evidence of adenylate cyclase activity nor cAMP in Xanthomonas, where a CRP-like protein, Clp, binds c-di-GMP instead of cAMP, suggesting that the Pil-Chp cluster may have a different output in this bacterium. This project intends to investigate the roles of the Pil-Chp ortologues in Xanthomonas citri, expanding the understanding of this conserved signaling system that may serve as a target for the development of anti-virulence drugs effective against both plant and human pathogens.