Influence of PAMP-induced systemic resistance in potato suspension cells and seedlings on defense signaling markers and infection with Phytophthora infestans

Colonization of roots by selected strains of fluorescent Pseudomonas spp. or their elicitors 
can trigger induced systemic resistance (ISR) against foliar pathogens in a plant species-specific 
manner. It has been suggested that early responses in cell suspension cultures in reply to 
rhizobacterial elicitors, such as generation of active oxygen species (AOS) and extracellular 
medium alkalinization (MA), are linked to the development of ISR in whole plants. In the present 
study, the pathogen-associated molecular patterns (PAMPs) i.e. lipopolysaccharides (LPS), 
siderophores, and the flagellin were tested for their effects on the induction of ISR in either potato 
cell suspension or seedlings. LPS among all PAMPs provoked an almost immediate burst in potato 
cell suspensions (H2O2 24.8 nmoles /g f. w. after 20 min). Filagellin showed a slower and weaker 
induction of AOS effect compared to LPS, whereas Siderophores did not show such induction. 
Siderophores were almost as active as LPS in induction of extracellular medium alkalinization, 
whereas flagellin was approximately half-so. In contrast to the refractoriness of the potato cells to 
re-stimulation of an oxidative burst with PAMPs, the cells here were able to almost fully re
alkalinize the medium upon repeated stimulation. All studied PAMPs were able to generate cell 
death in potato cell suspension to different levels. Northern blotting of the defense marker genes  
PAL, GST and ACO showed a remarkable induction at 3-9 hours post inoculation with the PAMPs 
and the induction effect subsided at 12-24 h. Potato suspension cells induced by Siderophores 
completely inhibited sporangia germination, whereas those induced by LPS led to deterioration of 
the sporangia. Elicitation of potato seedlings with all studied PAMPs resulted in significant 
reduction of disease index, AUDPC. Obtained significant correlation between ISR induction in 
potato cell suspension and seedlings suggested the potential to explore the response of potato plant 
to new elicitors with cell suspension first as it is a time and effort saving technique.