Double jeopardy: both overexpression and suppression of a redox-activated plant mitogen-activated protein kinase render tobacco plants ozone sensitive.
In plants, the role of mitogen-activated protein kinase (MAPK) in reactive oxygen species (ROS)-based signal transduction processes is elusive. Despite the fact that ROS can induce MAPK activation, no direct genetic evidence has linked ROS-induced MAPK activation with the hypersensitive response, a form of programmed cell death. In tobacco, the major ROS-induced MAPK is salicylate-induced protein kinase (SIPK). We found through gain-of-function and loss-of-function approaches that both overexpression and RNA interference-based suppression of SIPK render the plant sensitive to ROS stress. Transgenic lines overexpressing a nonphosphorylatable version of SIPK were not ROS sensitive. Analysis of the MAPK activation profiles in ROS-stressed transgenic and wild-type plants revealed a striking interplay between SIPK and another MAPK (wound-induced protein kinase [WIPK]) in the different kinotypes. During continuous ozone exposure, abnormally prolonged activation of SIPK was seen in the SIPK-overexpression genotype, without WIPK activation, whereas strong and stable activation of WIPK was observed in the SIPK-suppressed lines. Thus, one role of activated SIPK in tobacco cells upon ROS stimulation appears to be control of the inactivation of WIPK.
Samuel
Marcus A
MA
Biotechnology Laboratory, University of British Columbia, Vancouver, British Columbia, V6T 1Z3 Canada.
Ellis
Brian E
BE
D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D010083:Oxidants, Photochemical / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010126:Ozone / Q000494:pharmacology*; D010940:Plant Proteins; D030821:Plants, Genetically Modified; D015398:Signal Transduction / Q000502:physiology; D014026:Nicotiana / Q000166:cytology / Q000187:drug effects* / Q000235:genetics
D010083:Oxidants, Photochemical; D010940:Plant Proteins; D010126:Ozone; D006861:Hydrogen Peroxide; D020928:Mitogen-Activated Protein Kinases; C106405:SA-induced protein kinase; C113423:WIPK protein, Nicotiana tabacum