Widely conserved attenuation of plant MAMP-induced calcium influx by bacteria depends on multiple virulence factors and may involve desensitization of host pattern recognition receptors
Journal
Molecular Plant-Microbe Interactions
Journal Volume
32
Journal Volume
32
Journal Issue
5
Journal Issue
5
Pages
608-621
Start Page
608
End Page
621
ISSN
08940282
Date Issued
2019-05
Author(s)
Lammertz, Meltem
Kuhn, Hannah
Pfeilmeier, Sebastian
Malone, Jacob
Zipfel, Cyril
Kwaaitaal, Mark
Kvitko, Brian H.
Panstruga, Ralph
Abstract
Successful pathogens must efficiently defeat or delay host immune responses, including those triggered by release or exposure of microbe-associated molecular patterns (MAMPs). Knowledge of the molecular details leading to this phenomenon in genuine plant-pathogen interactions is still scarce. We took advantage of the well-established Arabidopsis thaliana-Pseudomonas syringae pv. tomato DC3000 pathosystem to explore the molecular prerequisites for the suppression of MAMP-triggered host defense by the bacterial invader. Using a transgenic Arabidopsis line expressing the calcium sensor apoaequorin, we discovered that strain DC3000 colonization results in a complete inhibition of MAMP-induced cytosolic calcium influx, a key event of immediate-early host immune signaling. A range of further plant-associated bacterial species is also able to prevent, either partially or fully, the MAMPtriggered cytosolic calcium pattern. Genetic analysis revealed that this suppressive effect partially relies on the bacterial type III secretion system (T3SS) but cannot be attributed to individual members of the currently known arsenal of strain DC3000 effector proteins. Although the phytotoxin coronatine and bacterial flagellin individually are dispensable for the effective inhibition of MAMP-induced calcium signatures, they contribute to the attenuation of calcium influx in the absence of the T3SS. Our findings suggest that the capacity to interfere with early plant immune responses is a widespread ability among plant-associated bacteria that, at least in strain DC3000, requires the combinatorial effect of multiple virulence determinants. This may also include the desensitization of host pattern recognition receptors by the prolonged exposure to MAMPs during bacterial pathogenesis.
Publisher
American Phytopathological Society
Type
journal article