title: The Stringent Response Mediated by (p)ppGpp Is Required for Virulence of Pseudomonas syringae pv. tomato and Its Survival on Tomato.
abstract: The hypersensitive response and pathogenicity (hrp) type III secretion system (T3SS) is a key pathogenicity factor in Pseudomonas syringae pv. tomato DC3000 (DC3000). In this study, the role of the second messenger (p)ppGpp on virulence and survival of DC3000 was investigated. Results have demonstrated that (p)ppGpp-deficient mutant (ppGpp(0)) of DC3000 exhibited lower levels of expression of the T3SS and genes of other virulence traits, such as coronatine toxin. The ppGpp(0) mutant of DC3000 was greatly impaired in causing disease and in growth in planta. Furthermore, (p)ppGpp was required for swarming motility, pyoverdine production, the oxidative stress response, as well as γ-amino butyric acid utilization. Screening of amino acids, major signals in activation of ppGpp biosynthesis, revealed that promoter activities of the avrPto gene could be either activated or suppressed by various amino acids in a ppGpp-dependent or -independent manner. Moreover, the ppGpp(0) mutant exhibited increased cell size and decreased survival on plant surfaces. Altogether, these findings indicate that ppGpp acts as an internal signal that regulates the T3SS as well as other virulence factors in pseudomonads and suggest that bacterial pathogens utilize intracellular messengers to sense environmental and nutritional signals for rapid, precise, and reversible control of their pathogenesis and survival.
authors: 1 Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, U.S.A.;
authors: Tiyakhon
authors: T
authors: Chatnaparat
authors: 2 Metabolomics Center, Roy J. Carver Biotechnology Center, University of Illinois at-Urbana-Champaign;
authors: Zhong
authors: Z
authors: Li
authors: 3 Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign;|4 Department of Biology, University of Massachusetts Boston, Boston, MA 02125, U.S.A.
authors: Schuyler S
authors: SS
authors: Korban
authors: 1 Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, U.S.A.;
authors: Youfu
authors: Y
authors: Zhao
mesh_terms: D000596:Amino Acids / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D054884:Host-Pathogen Interactions; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007192:Indenes; D018551:Solanum lycopersicum / Q000382:microbiology*; D009154:Mutation; D009842:Oligopeptides / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology; D011401:Promoter Regions, Genetic; D044224:Pseudomonas syringae / Q000187:drug effects / Q000235:genetics* / Q000472:pathogenicity*; D015398:Signal Transduction; D037521:Virulence Factors / Q000235:genetics; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D007192:Indenes; D009842:Oligopeptides; D037521:Virulence Factors; D005680:gamma-Aminobutyric Acid; C058487:coronatine; C042453:pyoverdin; D006861:Hydrogen Peroxide