Transposon mutagenesis of Pseudomonas syringae pvs. syringae and morsprunorum to identify genes required to cause bacterial canker disease of cherry.

Neale, Helen and Arnold, Dawn and Jackson, Rob and Hulin, Michelle and Harrison, Richard (2021) Transposon mutagenesis of Pseudomonas syringae pvs. syringae and morsprunorum to identify genes required to cause bacterial canker disease of cherry. UWE https://researchdata.uwe.ac.uk/id/eprint/627/

Brief summary of project

Bacterial canker of Prunus, affecting economically important stone fruit crops including cherry, peach, apricot and plum, is caused by the plant pathogen Pseudomonas syrinage (P.s.). Strains from two pathovars P.s. pv. syringae (Pss) and P.s. pv. morsprunorum race 1 (PsmR1) and 2 (PsmR2) in three phylogenetically distant clades have convergently evolved to infect Prunus. The bacteria enter woody tissues through wounds and leaf scars causing black necrotic cankers. Symptoms are also produced on blossom, fruit and leaves. Little is known about the mechanisms P.s. uses to colonise tree hosts such as Prunus. Here we created transposon (Tn) mutant libraries in one strain of P.s. from each of the three clades and screened the mutants on immature cherry fruit to look for changes in virulence. Mutants (242) with either reduced or enhanced virulence were detected and further characterised by in vitro screens for biofilm formation, swarming ability, and pathogenicity on leaves and cut shoots. In total 18 genes affecting virulence were selected, and these were involved in diverse functions including motility, Type III secretion, membrane transport, amino acid synthesis, DNA repair and primary metabolism. Interestingly, mutation of the effector gene hopAU1, led to an increase in virulence in Psm R2.