Regulation of ethylene biosynthesis at the level of 1-aminocyclopropane-1-carboxylate oxidase (ACO) gene

Ethylene, a gaseous plant hormone regulates essentially all physiological processes during the plant's life cycle. The practical implications of ethylene biosynthesis regulation for plant improvement have supported the continuous basic research on dissecting the structure of genes encoding ethylene biosynthetic enzymes, their differential expression patterns, and mechanisms underlying their transcriptional activity. ACC oxidase (ACO) is involved in the final step of ethylene production in plant tissues. In various plants several ACO isoforms have been isolated which are encoded by a multigenic family. There is a strong evidence that ACO gene expression is positively correlated to the ethylene production rates and its multiple isoforms are under development and environmental control. Thus, the regulation of ACO gene activity may act either as an additional or in several cases also as a main level for controlling ethylene biosynthesis in higher plants. This review summarizes in detail the knowledge about organization and gene structure, and transcriptional expression of ACO genes from different plant species. The perspectives of manipulating ACO gene as a method in biotechnological modification of ethylene synthesis are also discussed.