title: Chemical facilitation and induced pathogen resistance mediated by a root-secreted phytotoxin.
abstract: The flavonol (+/-)-catechin is an allelochemical produced by the invasive weed Centaurea maculosa (spotted knapweed). The full effects of (+/-)-catechin on plant communities in both the native and the introduced ranges of C. maculosa remain uncertain. Here, by supplementing plant growth media with (+/-)-catechin, we showed that low (+/-)-catechin concentrations may induce growth and defense responses in neighboring plants. Doses of the allelochemical lower than the minimum inhibitory concentration (MIC) induced growth in Arabidopsis thaliana; plants treated with 25 microg ml(-1) (+/-)-catechin accumulated more than twice the biomass of untreated control plants. Further, pretreatment of A. thaliana roots with low concentrations of (+/-)-catechin induced resistance to the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 in A. thaliana leaves. Low doses of (+/-)-catechin resulted in moderate increases in reactive oxygen species (ROS) in the meristems of treated plants, which may have loosened the cell walls and thus increased growth. Experiments with A. thaliana mutants indicated that (+/-)-catechin induces pathogen resistance by up-regulating defense genes via the salicylic acid (SA)/nonexpressor of pathogenesis related protein 1 (NPR1)-dependent pathway. Our results suggest that the growth and defense-inducing effects of (+/-)-catechin are concentration dependent, as (+/-)-catechin at higher concentrations is phytotoxic, thus suggesting the potential for hormesis to occur in nature.
authors.affiliation: Department of Plant and Animal Sciences, Nova Scotia Agricultural College, Truro, Nova Scotia, Canada B2N 5E3.
authors.forename: Balakrishnan
authors.initials: B
authors.lastname: Prithiviraj
authors.affiliation: Center for Rhizosphere Biology and.|Department of Forest, Rangeland, and Watershed Stewardship, Colorado State University, Fort Collins, CO 80523-1173, USA.
authors.forename: Laura G
authors.initials: LG
authors.lastname: Perry
authors.affiliation: Center for Rhizosphere Biology and.
authors.forename: Dayakar V
authors.initials: DV
authors.lastname: Badri
authors.affiliation: Center for Rhizosphere Biology and.
authors.forename: Jorge M
authors.initials: JM
authors.lastname: Vivanco
mesh_terms: D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism* / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D002392:Catechin / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D010937:Plant Growth Regulators / Q000494:pharmacology*; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000096:biosynthesis; D018517:Plant Roots / Q000378:metabolism* / Q000382:microbiology; D018520:Plant Shoots / Q000382:microbiology; D044224:Pseudomonas syringae / Q000472:pathogenicity*; D017382:Reactive Oxygen Species / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism; D014118:Toxins, Biological / Q000494:pharmacology*
chemical_list: D029681:Arabidopsis Proteins; C105496:NPR1 protein, Arabidopsis; D010937:Plant Growth Regulators; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D014118:Toxins, Biological; C053376:pathogenesis-related proteins, plant; D002392:Catechin; D020156:Salicylic Acid