Hr-Positive Phenotype of the Pseudomonas syringae pv. syringae hrpK Mutant and hrp Gene Superinduction in Tobacco Leaves Treated with Protein Synthesis Inhibitors

Abstract

Induction period-dependent expression of bacterial hrp (hypersensitive response and pathogenicity) genes is required to cause the hypersensitive reaction (HR) in an incompatible piani. Early induced resistance (EIR) is described as a local and fast (in 3-6 h) developing, light-independent reaction of plants thai can prevent HR. Recently it was found that the same bacterial inoculum can trigger both EIR and HR. A short heai-treatment (50°C, 15 sec) or cycioheximide nullifies EIR’s effect. Here we show thai in heat- or cycloheximide-treated incompatible tobacco leaves, hrpK mutant of Pseudomonas syringae pv. syringae 61 is able to induce the HR, having a significantly longer induction period (3-4 h) than the wild-type parent strain (1 h). Moreover, mutant’s growth is potentiated and hrpK gene is superinduced under these EiR-inhibitory conditions. These data suggest that 1) hrpK mutant triggers EIR beside having the capacity for inducing HR; 2) a mutation in brpK gene extends HR induction period; 3) the faster developing EIR relative to this delayed HR-inducing activity may be responsible for the HR(-)-phenotype of hrpK mutant; 4) the HR-preventive effect of EIR may involve inhibition of hrp gene activity of incompatible bacterial pathogens.KeywordsInduction PeriodHypersensitive ReactionElectrolyte LeakageTobacco LeaveProtein Synthesis InhibitorThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.