Cell-cell signal-dependent dynamic interactions between HD-GYP and GGDEF domain proteins mediate virulence in Xanthomonas campestris.

Journal article

RpfG is a paradigm for a class of widespread bacterial two-component regulators with a CheY-like receiver domain attached to a histidine-aspartic acid-glycine-tyrosine-proline (HD-GYP) cyclic di-GMP phosphodiesterase domain. In the plant pathogen Xanthomonas campestris pv. campestris (Xcc), a two-component system comprising RpfG and the complex sensor kinase RpfC is implicated in sensing and responding to the diffusible signaling factor (DSF), which is essential for cell-cell signaling. RpfF is involved in synthesizing DSF, and mutations of rpfF, rpfG, or rpfC lead to a coordinate reduction in the synthesis of virulence factors such as extracellular enzymes, biofilm structure, and motility. Using yeast two-hybrid analysis and fluorescence resonance energy transfer experiments in Xcc, we show that the physical interaction of RpfG with two proteins with diguanylate cyclase (GGDEF) domains controls a subset of RpfG-regulated virulence functions. RpfG interactions were abolished by alanine substitutions of the three residues of the conserved GYP motif in the HD-GYP domain. Changing the GYP motif or deletion of the two GGDEF-domain proteins reduced Xcc motility but not the synthesis of extracellular enzymes or biofilm formation. RpfG-GGDEF interactions are dynamic and depend on DSF signaling, being reduced in the rpfF mutant but restored by DSF addition. The results are consistent with a model in which DSF signal transduction controlling motility depends on a highly regulated, dynamic interaction of proteins that influence the localized expression of cyclic di-GMP.

Authors: Ryan, R; McCarthy, Y; Andrade, M; Farah, C; Armitage, J

• Publication status: Published
• Journal: Proceedings of the National Academy of Sciences of the United States of America
• Volume: 107
• Issue: 13
• Pages: 5989-5994
• Publication date: 2010-03-01
• DOI: 10.1073/pnas.0912839107
• EISSN: 1091-6490
• ISSN: 0027-8424
• Language: English
• Keywords: Signal Transduction; Bacterial Proteins; Recombinant Proteins; Xanthomonas campestris; Two-Hybrid System Techniques; Protein Structure, Tertiary; Plants; Protein Interaction Domains and Motifs; Fluorescence Resonance Energy Transfer; Microbial Interactions; Mutagenesis, Site-Directed; Virulence; Amino Acid Substitution