Conserved effectors underpin the virulence of liverwort-isolatedPseudomonasin divergent plants

Plant pathogenicPseudomonasspecies naturally antagonize a diverse range of flowering plants. While emerging research demonstrates that isolates belonging to theP. syringaespecies complex colonize diverse hosts, the extent to which these bacteria naturally infect non-flowering plants like the model liverwortMarchantia polymorpharemains unclear. Here, we identify natural associations betweenPseudomonas viridiflavaand the liverwortMarchantia polymorpha. Pseudomonasbacteria isolated from diseased liverworts in the wild successfully re-infectedM. polymorphain pure culture conditions, producing highin plantabacterial densities and causing prominent tissue maceration. Comparative genomic analysis ofMarchantia-associatedP. viridiflavaidentified core virulence machinery like the type-III secretion system (T3SS) and conserved effectors (AvrE and HopM1) that were essential for liverwort infection. Disease assays performed inNicotiana benthamianafurther confirmed that liverwort-associatedP. viridiflavainfect flowering plants in an effector-dependent manner. Our work highlightsP. viridiflavaas an effective broad host pathogen that relies on conserved virulence factors to manipulate evolutionarily divergent host plants.