title: A multi-repeat adhesin of the phytopathogen, Pectobacterium atrosepticum, is secreted by a Type I pathway and is subject to complex regulation involving a non-canonical diguanylate cyclase.
abstract: Cyclic diguanylate (c-di-GMP) is a second messenger controlling many important bacterial processes. The phytopathogen Pectobacterium atrosepticum SCRI1043 (Pba1043) possesses a Type I secretion system (T1SS) essential for the secretion of a proteinaceous multi-repeat adhesin (MRP) required for binding to the host plant. The genes encoding the MRP and the T1SS are tightly linked to genes encoding several putative c-di-GMP regulatory components. We show that c-di-GMP regulates secreted MRP levels in Pba1043 through the action of two genes encoding predicted diguanylate cyclase (DGC) and phosphodiesterase proteins (ECA3270 and ECA3271). Phenotypic analyses and quantification of c-di-GMP levels demonstrated that ECA3270 and ECA3271 regulate secreted MRP levels by increasing and decreasing, respectively, the intracellular levels of c-di-GMP. Moreover, ECA3270 represents the first active DGC reported to have an alternative active-site motif from the 'canonical' GG[D/E]EF. ECA3270 has an A-site motif of SGDEF and analysis of single amino acid replacements demonstrated that the first position of this motif can tolerate functional substitution. Serine in position one of the A-site is also observed in many other DGCs. Finally, another T1SS-linked regulator (ECA3265) also plays an important role in regulating secreted MRP, with an altered localization of MRP observed in an ECA3265 mutant background. Mutants defective in these three T1SS-linked regulators exhibit a reduction in root binding and virulence, confirming that this complex, finely tuned regulation system is crucial in the interaction with host plants.
authors: Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK.
authors: Daniel
authors: D
authors: Pérez-Mendoza
authors: Sarah J
authors: SJ
authors: Coulthurst
authors: Sonia
authors: S
authors: Humphris
authors: Emma
authors: E
authors: Campbell
authors: Martin
authors: M
authors: Welch
authors: Ian K
authors: IK
authors: Toth
authors: George P C
authors: GP
authors: Salmond
mesh_terms: D018829:Adhesins, Bacterial / Q000378:metabolism*; D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D044043:Pectobacterium / Q000378:metabolism* / Q000472:pathogenicity; D010727:Phosphoric Diester Hydrolases / Q000235:genetics / Q000378:metabolism*; D019761:Phosphorus-Oxygen Lyases / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000382:microbiology; D011198:Solanum tuberosum / Q000382:microbiology; D014774:Virulence
chemical_list: D018829:Adhesins, Bacterial; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D050505:Mutant Proteins; C062025:bis(3',5')-cyclic diguanylic acid; D010727:Phosphoric Diester Hydrolases; D019761:Phosphorus-Oxygen Lyases; C060720:diguanylate cyclase; D006152:Cyclic GMP