Ethylene action

Sozzi GO, Trinchero GD and Fraschina AA. 1999. Controlled-atmosphere storage of tomato fruit low oxygen or elevated carbon dioxide levels alter galactosidase activity and inhibit exogenous ethylene action. J Sci Food Agric 79(8) 1056—1070. 

The ripening of nonclimacteric fruits is usually considered as a process that as a whole does not require ethylene. Nevertheless, endogenous ethylene is involved at some steps of development of these fruits. In general, chlorophyll degradation in nonclimacteric fruits is believed to be ethylene stimulated, whereas the synthesis of pigments can depend on ethylene action or not. ... 

Ethylene action depends on binding to a receptor site that has a low affinity for other olefines. Oxygen is required for the response, which is competitively inhibited by carbon dioxide. 

The influence of Ag+ and CO on ethylene action was observed in senescing tobacco leaf disks in which loss of chlorophyll was taken as an index of senescence (Fig. 7). 

Silver ions923 and 2,5-norbornadiene (NBD)924 are well known as effective inhibitors of ethylene action. Silver, applied in the form of thiosulfate (silver thiosulfate (STS)), is a very effective inhibitor of ethylene action. It has been used with much success on cut flowers and potted plants. But as it is a heavy metal it cannot be used on food and feed, and is harmful to environment. As NBD requires continuous exposure and a high concentration, and has a strong odor, it also cannot be used on cut flowers and food. Furthermore, both compounds are toxic for plant growth in high concentration. 

In the late 1990s, Sisler and Serek925 discovered 1-methylcylopropene (1-MCP) as the new inhibitor of ethylene action. Now 1-MCP is the most useful compound among recently developed inhibitors of ethylene responses. It is stable and active at a considerably lower concentration (0.5 nl 1 3). It binds almost irreversibly to the receptors. Therefore, the effect continues until the receptors replace de novo synthesized ones. Now it is available commercially. 

In some cases it might be desirable to inhibit ethylene synthesis chemically to prevent responses mediated by naturally produced ethylene or stress-produced ethylene. Although some substances do inhibit ethylene production modestly—e.g. TIBA (69)—no outstanding regulator of this nature has been discovered. Another possibility is to promote or inhibit ethylene action. Promotion can be accomplished by auxin transport inhibitors and GA in cases where auxins and ethylene have opposite effects 52, 53, 54, 55). Recently, silver ion was found to be a potent inhibitor of ethylene action (70). Ethylene action also can be inhibited by lowering the temperature and O2 level or increasing the CO2 level... 

Ethylene 6-1 is the simplest of the known plant growth regulators, and has a variety of physiological properties [49]. It appears to be active without metabolic conversion, so there is now no reason to regard ethylene in a different light from the other established plant hormones [50,51]. While many molecules are known to have ethylene activity, (some examples are given in Table 1), ethylene remains the most active. Inhibitors of ethylene action are also known, so that structure activity correlations fall into two categories. 

Fig. 9. Model for possible mode of ethylene action. A 5-coordinate intermediate could be the active species. (Reprinted with permission from Sisler, E.C. and Goren, R., Whafs New in Plant Physiology 12, 37 1981).

Giridhar, R Indu, E.R Vinod, K Chandrashekar, A. Ravishankar, G.A. CasteUanos-Hernandez, O.A. (2004). Direct somatic embryogenesis from Coffea arabica L. and Coffea canephora P. ex Fr. under the influence of ethylene action inhibitor-silver nitrate. Acta Physiologiae Plantarum, Vol.26, No.3, (September 2004), p>p. 299-305, ISSN 1861-1664... 

It was later shown that apically applied auxin was also concentrated at the nodes [2]. However, Burg and Burg felt that this general idea might apply better to other inhibitions produced by applied auxin, such as the inhibition of root growth. This reserve was due inter alia to their observation that high CO2 concentrations, which inhibit ethylene action, did not release the buds from inhibition. However,... 

Incubation of unwounded tissue in a closed container in the presence of several pieces of wounded tissue does not cause polysome formation, whereas treatment with the gaseous inhibitor of ethylene action, norbornadiene does (not shown). This... 

Van der Molen et al. (138) presented evidence that occlusion of the vascular system, which occurs during the wilting of plants, is a direct consequence of ethylene action. They propose that a common signal for the formation of vascular gels... 

Taken together these results indicate a very complex crosstalk between PAs and various components of ethylene action. The complexity is partly driven by the presence of a family of genes for both the biosynthesis and action of ethylene, each under a complex developmental and environmental regulation. Homologues of various gene families not only are redundant in some cases and take over the function of their counterpart, but also their transcription can compensate the loss/inexpression of a family member (Tieman et al. 2000). 

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