Overexpression of SIPK in tobacco enhances ozone-induced ethylene formation and blocks ozone-induced SA accumulation.
Ozone induces rapid activation of SIPK, a mitogen-activated protein kinase (MAPK) in tobacco. Through transgenic manipulation it has previously been shown that overexpression of SIPK leads to enhanced ozone-induced lesion formation with concomitant accumulation of ROS. In spite of this hypersensitive phenotype, the effect of this altered SIPK expression on the levels of various hormones that regulate ozone-induced cell death has remained unexplored. The response of both salicylate and ethylene, the major phytohormones that modulate ozone-induced cell death, have now been analysed in SIPK-OX tobacco plants. Ozone treatment strongly induced ethylene formation in the sensitive SIPK-OX plants at ozone concentrations that failed to elicit stress ethylene release in WT plants. By contrast, SIPK-overexpressing plants displayed no ozone-induced SA accumulation, whereas WT plants accumulated SA upon ozone exposure. Epistatic analysis of SIPK-OX function suggests that the ozone-induced cell death observed in SIPK-OX plants is either independent, or upstream, of SA accumulation.
Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC, Canada V6T 1Z4. smarcus@interchange.ubc.ca
Marcus A
MA
Samuel
Ankit
A
Walia
Shawn D
SD
Mansfield
Brian E
BE
Ellis
D017209:Apoptosis / Q000502:physiology; D015536:Down-Regulation; D005030:Ethylenes / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010126:Ozone / Q000494:pharmacology*; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000378:metabolism; D030821:Plants, Genetically Modified; D020156:Salicylic Acid / Q000378:metabolism*; D015398:Signal Transduction; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism*
D005030:Ethylenes; D010940:Plant Proteins; D010126:Ozone; C036216:ethylene; D020928:Mitogen-Activated Protein Kinases; C106405:SA-induced protein kinase; D020156:Salicylic Acid