2002/05/01 by Kevin L.-C. Wang, Hai Li, Joseph R. Ecker · 2 citations
Agricultural and Biological Sciences · #Plant Physiology and Cultivation Studies #Postharvest Quality and Shelf Life Management #Plant Molecular Biology Research
paper · pdf · doi:10.1105/tpc.001768
openalex publication_date 2002/05/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29
Despite its simple two-carbon structure, the olefin ethylene is a potent modulator of plant growth and development (Ecker, 1995). The plant hormone ethylene is involved in many aspects of the plant life cycle, including seed germination, root hair development, root nodulation, flower senescence, abscission, and fruit ripening (reviewed in Johnson and Ecker, 1998). The production of ethylene is tightly regulated by internal signals during development and in response to environmental stimuli from biotic (e.g., pathogen attack) and abiotic stresses, such as wounding, hypoxia, ozone, chilling, or freezing. To understand the roles of ethylene in plant functions, it is important to know how this gaseous hormone is synthesized, how its production is regulated, and how the signal is transduced. Morphological changes in dark-grown (etiolated) seedlings treated with ethylene or its metabolic precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), have been termed the triple response. The exaggerated curvature of the apical hook, radial swelling of the hypocotyl, and shortening of the hypocotyl and root are the unmistakable hallmarks of this ethylene response. Over the past decade, the triple response phenotype has been used to screen for mutants that are defective in ethylene responses (Bleecker et al., 1988; Guzman and Ecker, 1990). Etiolated Arabidopsis seedlings with minor or no phenotypic response upon ethylene application are termed ethylene-insensitive (ein) or ethylene-resistant (etr) mutants. Mutants have also been identified that display a constitutive triple response in the absence of ethylene (Kieber et al., 1993; Roman and Ecker, 1995). This class can be divided into subgroups based on whether or not the constitutive triple response can be suppressed by inhibitors of ethylene perception and biosynthesis, such as silver thiosulfate and aminoethoxyvinyl glycine (AVG). Mutants that are unaffected by these inhibitors are termed constitutive triple-response (ctr) mutants, whereas mutants whose phenotype reverts to normal morphology are termed ethylene-overproducer (eto) mutants, which are defective in the regulation of hormone biosynthesis. The genetic hierarchy among ethylene biosynthesis and signaling pathway components in Arabidopsis has been established by epistasis analysis using these mutants (Solano and Ecker, 1998; Stepanova and Ecker, 2000). The intent of this review is not to cover all aspects of ethylene biology but to focus on recent findings. In particular, we examine interaction of ethylene and two other plant growth regulators, jasmonic acid (JA) and salicyclic acid (SA), and their roles in mediating responses to biotic and abiotic stresses. We begin by summarizing what is currently known about the mechanism and regulation of ethylene biosynthesis and by providing an update of our current understanding of the ethylene signaling pathway. Biosynthetic Pathway and Regulation of Ethylene. The formation of S-AdoMet is catalyzed by SAM synthetase from the methionine at the expense of one molecule of ATP per molecule of S-AdoMet synthesized. S-AdoMet is the methyl group donor for many cellular molecules (Methylated Acceptors), including nucleic acids, proteins, and lipids. In addition, S-AdoMet is the precursor of the polyamine synthesis pathway (Spermidine/Spermine biosynthesis pathway). ACC is the immediate precursor of ethylene. The rate-limiting step of ethylene synthesis is the conversion of S-AdoMet to ACC by ACC synthase under most conditions. MTA is the by-product generated along with ACC production by ACC synthase. Recycling of MTA back to methionine conserves the methylthio group and is able to maintain a constant concentration of cellular methionine even when ethylene is rapidly synthesized. Malonylation of ACC to malonyl-ACC (MACC) deprives the ACC pool and reduces the ethylene production. ACC oxidase catalyses the final step of ethylene synthesis using ACC as substrate and generates carbon dioxide and cyanide. Transcriptional regulation of ACC synthase and ACC oxidase is by of ACC synthase is and be by and the by stresses. and of ACC synthase are the ACC synthase be or in is with ACC synthase at the and be from the it is by at the S-AdoMet is the precursor for ethylene biosynthesis (reviewed in and In to an of of cellular methionine is to S-AdoMet by S-AdoMet synthetase at the expense of ATP et al., 1998). S-AdoMet is the methyl donor in and is used as a substrate for many including and ethylene biosynthesis et al., 1998). In addition, S-AdoMet is involved in that proteins, and nucleic the of the cycle, the step of ethylene biosynthesis is the conversion of S-AdoMet to ACC by ACC synthase (reviewed in and In to ACC synthase also in this which is to methionine by using a methionine (reviewed in and 2000). This pathway the methyl group for of ethylene production. ethylene can be an pool of the the group of the methionine is also ACC is by ACC oxidase to and which is to by synthase to of during of ethylene synthesis The rate-limiting step of ethylene synthesis is the conversion of S-AdoMet to ACC by ACC synthase (reviewed in The that of the is regulated by a of signals and that ACC synthase is and at that ethylene biosynthesis is tightly and regulation of ethylene biosynthesis have been in plant (reviewed in 1993; et al., 1998; et al., 2000). of to be the in and are regulated, and is regulated by ethylene during fruit ripening et al., 1998). regulation have on in response to and environmental The in is that the are and regulated and are by internal and to plant ACC by their and (reviewed in ACC synthase is by a whose the of et al., is an for that is in the of The of from has been and that the a et al., are and ACC but also the of the the can be on that of of the among the of the are on the and are the of the The substrate of these from the in the which is by the of of ACC synthase and of in the The is by a with the most from the are two of a and a that are by the The the of the and the among of The which in ACC and of the most and of the The with a is to the by the two of the in the that with in ACC and in are from the the that ACC synthase as a and 1998). and in have been used to the and et al., 1998). at these the et al., et al., 1998). of two ACC with the in a et al., 1998). of their in ethylene biosynthesis, the regulation of ACC has been an the of from and many have been identified and from plant including and Arabidopsis (reviewed in Johnson and Ecker, 1998; et al., 2000). is that of ACC synthase are regulated et al., and 1998; et al., 2000). of from other of the have been the identified from Arabidopsis can be used to this In have been et al., et al., and et al., 2000). is by wounding, and of ethylene The with ethylene regulation of et al., et al., is in seedlings by and et al., et al., 1995). is by and a concentration of in seedlings et al., et al., can be by to in and by it can also be by and ethylene et al., 1998; and et al., and 2000). identified as one of the of which of Arabidopsis in response to et al., 2000). most of the the is that are and regulated by et al., is that in of on the the of is In and not in or et al., 1995). is a which is the and be for et al., 1995). of this from the other is to be a from a of is to about the of in that it is and by signals that other is that as a of with other the of regulation of et al., et al., et al., of to a in which is rapidly by of the inhibitors or et al., with the not of the but also the of on by of inhibitors the the are the to be a of that synthesis is to or the upon and that be not a in the of per is known that is in and at it is that of its to the with this from and et al., an of be by recent the of regulation of et al., and ethylene mutants, and have been identified from Arabidopsis and Ecker, et al., is a whereas and are The constitutive triple-response phenotype of the mutants can be suppressed by silver thiosulfate or that these mutants are in the regulation of ethylene biosynthesis. has been that of to ethylene production in seedlings of Arabidopsis and changes the triple response by ethylene et al., 1995). the of these termed mutants to have been by for to et al., in one of these to and et al., and to to et al., of from the has that a to an of the of The of changes the from to The other of are the ethylene production in seedlings is that of the that the is not the of et al., In addition, ethylene production not with an of with ethylene the of by The of these is that ethylene synthesis by The in be the for such The of such in the that can roles in and ethylene biosynthesis. has been to be in response to and The of identified as by acid of and of The of in has also been by with from the fruit and in by using a to In addition, the for is of from that a is the of most The in is at an as the in of which is in the of the not a in that the in the a for regulation that be by at of not its the of in an in ethylene production. that has it is that the in is the by the of of or by the of this the of these a for the regulation of is In this the of a is that with the of and its by of This interaction the of or its in of to its of the of the or it and to the as a that a for other for of a in of the the of the of the in from many regulation a mechanism to changes in a for The of the Arabidopsis ethylene and Ecker, that is a for the of the past decade, of ethylene biosynthesis have on the and of and from a of plant with an to understanding the signals that the of these about the regulation of these how such as and a of biotic and abiotic stresses, such as or pathogen the ethylene from plant the of the Arabidopsis a of and have been identified that for This the of for and and whether these have and molecules that or as as such as and that of the in ethylene biosynthesis are to understand the of regulation and to the components involved in this of the are ethylene in and and and a and have been to as and have and a and have at their at the of the and a is for the a is involved in of to the ethylene In the absence of an ethylene ethylene a and in the ethylene response a of ethylene the in of which to as a of the ethylene pathway. the to the and the signals to the of in the to the of and its in an and other can with the in the of and ethylene is by a of that are to involved in environmental The of two a as the that an internal in response to environmental and a response that the components upon a from the of the on its and ethylene in and et al., 1993; et al., and 1998; et al., 1998). these and a that to response at the of the of and has been in et al., et al., that not have and have been to the of other by with et al., 1998). the of the of the of the of the the can be divided into two The of and at the ethylene and et al., and a at the of the The which and is to have at the and a that one or for that these The that of a of the have a to but et al., the that the class of not as but as and of the ethylene have into the mechanism of regulation in and identified as ethylene-insensitive (Bleecker et al., 1988; Roman et al., et al., 1998; et al., 1998). into the of and the ethylene their in ethylene perception et al., 1995). of the of and by for of the mutants genetic of how the ethylene and 1998). 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This also that the is in to ethylene and that the ethylene-insensitive is an of This is to the that is known to be to ethylene most including the for most of the ethylene response mutants et al., 1995). among and in response in ACC ethylene and or has been as an the and is as an abiotic that plant responses on by pathogen et al., 1998). to to an which a response to that by the response upon pathogen et al., from the is a of on cellular and by it by signals from as for the response and of has been to be the for response and the of which is for the response and et al., generated by from its with and other cellular components when it from the by is by the to of an acid potent in Arabidopsis et al., has been to the of which and the of of the et al., The that a of of and the and the of their that an of by is for the by the the is such as that in as a of the response is rapidly and synthesis is one of the responses to et al., 1998; et al., 2000). 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