Ethylene regulates a multitude of plant processes, ranging from seed germination to organ senescence. Of particular economic importance is the role of ethylene as an inducer of fruit ripening. Ethylene is synthesized from -adenosyl-L-methionine via 1-aminocyclopropane-1-carboxylic acid (ACC). The enzymes catalyzing the two reactions in this pathway are ACC synthase and ACC oxidase. Environmental and endogenous signals regulate ethylene biosynthesis primarily through differential expression of ACC synthase genes. Components of the ethylene signal transduction pathway have been identified by characterization of ethylene-response mutants in . One class of mutations, exemplified by , led to the identification of the ethylene receptors, which turned out to be related to bacterial two-component signaling systems. Mutations that eliminate ethylene binding to the receptor yield a dominant, ethylene-insensitive phenotype. encodes a Raf-like Ser/Thr protein kinase that acts downstream from the ethylene receptor and may be part of a MAP kinase cascade. Mutants in exhibit a constitutive ethylene-response phenotype. Both the ethylene receptors and CTR1 are negative regulators of ethylene responses. and are epistatic to , and mutations in either gene lead to ethylene insensitivity. Whereas the function of EIN2 in ethylene transduction is not known, EIN3 is a putative transcription factor involved in regulating expression of ethylene-responsive genes. Biotechnological modifications of ethylene synthesis and of sensitivity to ethylene are promising methods to prevent spoilage of agricultural products such as fruits, whose ripening is induced by ethylene.


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  • Article Type: Review Article
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