1-Aminocyclopropane-1-carboxylate synthase — genes and expression

The immediate precursor of ethylene in higher plants is 1-aminocyclopropane-1-carboxylic acid (ACC), which is a product of the reaction controlled by 1-aminocyclopropane-1-carboxylate synthase catalytic activity (S-adenosyl-L-methionine methylthioadenosine-lyase, EC 4.4.1.14). This review summarizes the up-to-date knowledge about organization and gene structure, and transcriptional expression of ACS genes from different plant species hitherto characterized. ACS is encoded by a highly divergent multigene family in each plant species. For example, the ACS families of tomato (LE-ACS) and Arabidopsis thaliana (AT-ACS) include numerous isoenzyme genes. Expression of selected members of the multigene ACS family in higher plants is induced by a diverse group of external and internal ethylene inducers such as: wounding, anaerobiosis, viral and fungal infection, chilling, drought, heavy metals, auxin, ripening and senescence processes. Enhanced transcription is the main regulatory step of this enzyme activity but the posttranscriptional regulation is operational as well.