title: Arabidopsis MAP kinase phosphatase 1 and its target MAP kinases 3 and 6 antagonistically determine UV-B stress tolerance, independent of the UVR8 photoreceptor pathway.
abstract: Plants perceive UV-B radiation as an informational signal by a pathway involving UVR8 as UV-B photoreceptor, activating photomorphogenic and acclimation responses. In contrast, the response to UV-B as an environmental stress involves mitogen-activated protein kinase (MAPK) signalling cascades. Whereas the perception pathway is plant specific, the UV-B stress pathway is more broadly conserved. Knowledge of the UV-B stress-activated MAPK signalling pathway in plants is limited, and its potential interplay with the UVR8-mediated pathway has not been defined. Here, we show that loss of MAP kinase phosphatase 1 in the mutant mkp1 results in hypersensitivity to acute UV-B stress, but without impairing UV-B acclimation. The MKP1-interacting proteins MPK3 and MPK6 are activated by UV-B stress and are hyperactivated in mkp1. Moreover, mutants mpk3 and mpk6 exhibit elevated UV-B tolerance and partially suppress the UV-B hypersensitivity of mkp1. We show further that the MKP1-regulated stress-response MAPK pathway is independent of the UVR8 photoreceptor, but that MKP1 also contributes to survival under simulated sunlight. We conclude that, whereas UVR8-mediated acclimation in plants promotes UV-B-induced defence measures, MKP1-regulated stress signalling results when UV-B protection and repair are insufficient and damage occurs. The combined activity of these two mechanisms is crucial to UV-B tolerance in plants.
authors.affiliation: Department of Botany and Plant Biology, University of Geneva, Sciences III, CH-1211 Geneva 4, Switzerland.
authors.forename: Marina A
authors.initials: MA
authors.lastname: González Besteiro
authors.forename: Sebastian
authors.initials: S
authors.lastname: Bartels
authors.forename: Andreas
authors.initials: A
authors.lastname: Albert
authors.forename: Roman
authors.initials: R
authors.lastname: Ulm
mesh_terms: D000064:Acclimatization; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D055786:Gene Knockout Techniques; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D017027:Protein Tyrosine Phosphatases; D014466:Ultraviolet Rays
chemical_list: D029681:Arabidopsis Proteins; D002868:Chromosomal Proteins, Non-Histone; C525052:Uvr8 protein, Arabidopsis; C458516:AtMPK3 protein, Arabidopsis; C436293:MPK6 protein, Arabidopsis; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C499612:MKP1 protein, Arabidopsis; D017027:Protein Tyrosine Phosphatases