The Phytophthora parasitica RXLR effector Penetration-SpecificEffector 1 favours Arabidopsis thaliana infection by interferingwith auxin physiology

摘要

Pathogenic oomycetes have evolved RXLR effectors to thwart plant defense mechanismsand invade host tissues. We analysed the function of one of these effectors (Penetration-Specific Effector 1 (PSE1)) whose transcript is transiently accumulated during penetration ofhost roots by the oomycete Phytophthora parasitica. Expression of PSE1 protein in tobacco (Nicotiana tabacum and Nicotiana benthamiana)leaves and in Arabidopsis thaliana plants was used to assess the role of this effector in plantphysiology and in interactions with pathogens. A pharmacological approach and marker lineswere used to charcterize the A. thaliana phenotypes. Expression of PSE1 in A. thaliana led to developmental perturbations associated with lowconcentrations of auxin at the root apex. This modification of auxin content was associatedwith an altered distribution of the PIN4 and PIN7 auxin efflux carriers. The PSE1 protein facilitatedplant infection: it suppressed plant cell death activated by Pseudomonas syringaeavirulence gene AvrPto and Phytophthora cryptogea elicitin cryptogein in tobacco andexacerbated disease symptoms upon inoculation of transgenic A. thaliana plantlets withP. parasitica in an auxin-dependant manner. We propose that P. parasitica secretes the PSE1 protein during the penetration process tofavour the infection by locally modulating the auxin content. These results support thehypothesis that effectors from plant pathogens may act on a limited set of targets, includinghormones.