Analysis of ethylene signal-transduction kinetics associated with seedling-growth response and chitinase induction in wild-type and mutant arabidopsis.
Kinetic aspects of ethylene-mediated signal transduction leading to seedling-growth inhibition and chitinase induction in Arabidopsis were investigated by the introduction of defined mutations in components of these pathways. Dose-response analysis of wild-type responses indicated that the rate-limiting steps for seedling responses and Arabidopsis basic-chitinase induction displayed Michaelis-Menten kinetics with apparent dissociation constants of the response (Kr) of 0.1 and 1.4 microL L-1 ethylene, respectively. In the ethylene-insensitive etr1-1 and ein2-32 mutant lines, both Arabidopsis basic-chitinase induction and seedling-growth responses were completely disrupted, whereas the weaker etr1-2 allele eliminated the chitinase-induction response but only partially disrupted the seedling responses. A heterologous reporter gene containing the chitinase promoter from bean (bean basic-chitinase-beta-glucuronidase) displayed subsensitive kinetics (Kr 120 microL L-1 ethylene) compared to the response of the endogenous basic-chitinase response (Kr 1.4 microL L-1 ethylene). A model for ethylene signal transduction that accounts for the observed variation in ethylene dose-response relationships is presented. The relationship between the model and the biochemical mechanisms of well-characterized signal-transduction systems in animals is discussed.
Chen
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QG
Botany Department, University of Wisconsin, Madison 53706, USA.
Bleecker
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AB
D000388:Air; D000483:Alleles; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D001483:Base Sequence; D002688:Chitinases / Q000096:biosynthesis* / Q000378:metabolism; D017931:DNA Primers; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D005030:Ethylenes / Q000494:pharmacology*; D007887:Fabaceae; D015870:Gene Expression; D017343:Genes, Plant; D005966:Glucuronidase / Q000096:biosynthesis; D007700:Kinetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010946:Plants, Medicinal; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*
D017931:DNA Primers; D005030:Ethylenes; D011993:Recombinant Fusion Proteins; C036216:ethylene; D002688:Chitinases; D005966:Glucuronidase