Ethylene insensitivity modulates ozone-induced cell death in birch.
We have used genotypic variation in birch (Betula pendula Roth) to investigate the roles of ozone (O(3))-induced ethylene (ET), jasmonic acid, and salicylic acid in the regulation of tissue tolerance to O(3). Of these hormones, ET evolution correlated best with O(3)-induced cell death. Disruption of ET perception by transformation of birch with the dominant negative mutant allele etr1-1 of the Arabidopsis ET receptor gene ETR1 or blocking of ET perception with 1-methylcyclopropene reduced but did not completely prevent the O(3)-induced cell death, when inhibition of ET biosynthesis with aminooxyacetic acid completely abolished O(3) lesion formation. This suggests the presence of an ET-signaling-independent but ET biosynthesis-dependent component in the ET-mediated stimulation of cell death in O(3)-exposed birch. Functional ET signaling was required for the O(3) induction of the gene encoding beta-cyanoalanine synthase, which catalyzes detoxification of the cyanide formed during ET biosynthesis. The results suggest that functional ET signaling is required to protect birch from the O(3)-induced cell death and that a decrease in ET sensitivity together with a simultaneous, high ET biosynthesis can potentially cause cell death through a deficient detoxification of cyanide.
Institute of Biotechnology and Department of Biosciences, University of Helsinki, POB 56 (Viikinkaari 9), Finland.
Jorma
J
Vahala
Raili
R
Ruonala
Markku
M
Keinänen
Hannele
H
Tuominen
Jaakko
J
Kangasjärvi
D000222:Adaptation, Physiological / Q000187:drug effects; D017209:Apoptosis / Q000187:drug effects*; D029662:Betula / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D003517:Cyclopentanes / Q000378:metabolism; D005030:Ethylenes / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007700:Kinetics; D008190:Lyases / Q000235:genetics; D008969:Molecular Sequence Data; D054883:Oxylipins; D010126:Ozone / Q000494:pharmacology*; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
D003517:Cyclopentanes; D005030:Ethylenes; D054883:Oxylipins; D012333:RNA, Messenger; D010126:Ozone; C011006:jasmonic acid; C036216:ethylene; D008190:Lyases; C019955:beta-cyanoalanine synthase; D020156:Salicylic Acid