The ethylene biosynthetic and signal transduction pathways are differently affected by 1-MCP in apple and peach fruit

1-Methylcyclopropene (1-MCP) is an antagonist of ethylene for receptor binding sites and the effects of its application differ in relation to a number of factors including genotype and ripening physiology. Peach (Prunus persica L. Batsch cv. 'Summer Rich') and apple (Malus x domestica L. Borkh cv. 'Golden Delicious') fruits were incubated with 1-MCP (1 mu L l(-1)) for 24 h at 20 degrees C and respiration rate, ethylene production and fruit firmness, together with ACC synthase, ACC oxidase, ETR1, ERS1, and CTR1 gene expression patterns were assessed throughout the post-treatment phase. 1-MCP was confirmed to be effective in delaying ripening in apples while in peaches only a limited effect of the chemical was observed. A dramatic inhibition of ethylene biosynthesis and ACS gene expression was induced by 1-MCP in apples whereas no marked difference was observed in peaches between the two controls (in air and in sealed jars without 1-MCP) and the treated fruit. In apples, Md-ETR1 and Md-ERS1 gene expression was down-regulated by 1-MCP starting from the end of the treatment, while Md-CTR1 appeared negatively affected by the chemical at a later stage. Transcription of Pp-ETR1, Pp-ERS1 and Pp-CTR1 genes appeared unaffected in 1-MCP treated peaches. Differences in receptor transcript levels between control fruit maintained in air and those enclosed in sealed jars without 1-MCP may be due to an effect of CO2 that rapidly accumulates following incubation of ripening peaches. Results support the hypothesis that the different behaviour of peaches and apples in response to 1-MCP application might be related to differences in terms of ratio, expression patterns and/or turn-over of the ethylene receptors.