The effect of water stress on 1-(malonylamino)cyclopropane-1-carboxylic acid concentration in plant tissues

Since the discovery of 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC) as a major metabolite of both endogenous and exogenously applied 1-aminocyclopropane-1-carboxylic acid (ACC), it has become evident that the formation of MACC from ACC can act to regulate ethylene production in certain tissues. Hence it was suggested that MACC could serve as an indicator of water-stress history in plant tissues. The accurate quantification of MACC in plant tissues is essential for understanding the role of MACC in the regulation of ethylene biosynthesis. Hoffman et al. [15] described a method for the measurement of MACC in which MACC was hydrolysed by HCl to ACC, which was then assayed by chemical oxidation to form ethylene. Attempts have been made by others to raise monoclonal antibodies to MACC so that an immunoassay could be developed in order to gain a deeper understanding of stress-induced ethylene production but no further publications have been forthcoming. Here a method employing GC-MS is compared with the indirect assay for MACC, which is based upon hydrolysis of MACC to ACC and conversion of ACC by hypochlorite reagent to ethylene which is subsequently quantified by GC.