Whole-transcriptome microarray analysis of different biovars of Pseudomonas syringae pv. actinidiae grown in rich medium or apoplast-like conditions

Purpose: Pseudomonas syringae pv. actinidiae (Psa) is a phytopathogen that causes devastating bacterial canker in kiwifruit. Among five biovars defined by genetic, biochemical and virulence traits, Psa3 is the most aggressive and is responsible for the most recent reported outbreaks, but the molecular basis of its heightened virulence is unclear. A custom P. syringae multi-strain whole-genome microarray platform, encompassing biovars Psa1, Psa2 and Psa3 and the well-established model P. syringae pv. tomato, was used to analyse early bacterial responses to an apoplast-like minimal medium. Conlusion: this work highlighted that diverse early responses to the host apoplast, even among bacteria belonging to the same pathovar, can lead to different virulence strategies and may explain the differing outcomes of infections. mRNA profiles of Psa1, Psa2 and Psa3 cells incubated in rich medium (optima growth conditions) were compared to mRNA profiles of Psa1, Psa2 and Psa3 cells grown in apoplast-mimicking medium. All mRNA profiles were generated from three biological replicates.