title: Pathogenicity of Pseudomonas syringae pv. tomato on tomato seedlings: phenotypic and gene expression analyses of the virulence function of coronatine.
abstract: Bacterial speck disease, which is caused by Pseudomonas syringae pv. tomato, is an economically important disease on tomato. In the present study, we show that P. syringae pv. tomato DC3000 is a pathogen of tomato seedlings, an aspect of pathogen biology that has not been previously investigated. This resulted in the development of a virulence assay on tomato seedlings that has several advantages over labor-intensive foliar assays, including a shorter growth and incubation period, ease of inoculation and handling, and rapid generation of larger sample sizes per experiment. The utility of this assay was investigated by exploring the virulence function of coronatine (COR) on tomato seedlings. Using the COR- mutant DB29 and a MAPMAN display of transcript data from TOM1 microarrays, COR-dependent expression of genes involved in secondary metabolism, polyamine biosynthesis, reactive oxygen species homeostasis, and the novel transcription factor SlNAC2 were identified. Furthermore, during pathogenesis, genes involved in photosynthetic light reactions and the Calvin-Benson cycle were strongly repressed by COR. In conclusion, we show that P. syringae pv. tomato infects tomato seedlings and that COR is required for virulence in seedlings. The seedling assay can be used in high-throughput screens for the identification of molecular targets for COR and for the identification of genes involved in pathogenesis.
authors.affiliation: Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA. sruppalapati@noble.org
authors.forename: Srinivasa Rao
authors.initials: SR
authors.lastname: Uppalapati
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ishiga
authors.forename: Tamding
authors.initials: T
authors.lastname: Wangdi
authors.forename: Ewa
authors.initials: E
authors.lastname: Urbanczyk-Wochniak
authors.forename: Takako
authors.initials: T
authors.lastname: Ishiga
authors.forename: Kirankumar S
authors.initials: KS
authors.lastname: Mysore
authors.forename: Carol L
authors.initials: CL
authors.lastname: Bender
mesh_terms: D000596:Amino Acids / Q000235:genetics / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D007192:Indenes; D018551:Solanum lycopersicum / Q000382:microbiology*; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D044224:Pseudomonas syringae / Q000235:genetics* / Q000472:pathogenicity; D020133:Reverse Transcriptase Polymerase Chain Reaction; D036226:Seedlings / Q000382:microbiology*; D014158:Transcription, Genetic; D014774:Virulence / Q000235:genetics
chemical_list: D000596:Amino Acids; D007192:Indenes; C058487:coronatine