African Journal of Biotechnology Vol. 3 (10), pp. 497-502, October 2004           
ISSN 1684–5315 © 2004 Academic Journals

Full Length Research Paper

Expression of a 1-aminocyclopropane-1-carboxylate (ACC) oxidase gene in peach (Prunus persica L.) fruit in response to treatment with carbon dioxide and 1-methylcyclopropene: possible role of ethylene

Francis M. Mathooko^1,*, Yuki Tsunashima², Yasutaka Kubo² and Akitsugu Inaba²

¹Department of Food Science and Technology, Faculty of Agriculture, Jomo Kenyatta University of Agriculture and Technology, P. O. Box 62000, Nairobi 00200, Kenya.

²Laboratory of Postharvest Agriculture, Faculty of Agriculture, Okayama University, Tsushima, Okayama 700-8530, Japan

*Correspondingauthor. E-Mail: mmathooko@yahoo.co.uk. Tel./Fax: +81 – 86 – 251 – 8337

Accepted 14 September, 2004

In this study we investigated the effect of exogenous ethylene treatment on ethylene production, 1-aminocyclopropane-1-carboxylate (ACC) oxidase activity and expression of an ACC oxidase (PP-ACO1) gene previously cloned (Mathooko et al., 2001) in peach (Prunus persica L.) fruit. We also investigated the mode of action of CO₂ and 1-methycyclopropene (1-MCP) in the regulation of ethylene biosynthesis during peach fruit ripening. Fruits were treated with various concentrations of ethylene (0.1, 1, 10, 100, 500, 1000 ppm) and also with CO₂ and 1-MCP in the presence or absence of 500 ppm ethylene. Ethylene stimulated ethylene production at concentrations of 100 ppm and above while ACC oxidase activity was stimulated in a concentration-dependent manner. PP-ACO1 was slightly constitutively expressed and exogenous ethylene stimulated accumulation of its mRNA transcript in a concentration-dependent manner up to 100 ppm after which the level remained constant. CO₂ and 1-MCP inhibited the ethylene-stimulated ethylene production, ACC oxidase activity and accumulation of PP-ACO1 transcripts by about 50%. These results indicate that ethylene plays a key role in the regulation of ethylene production and ACC oxidase activity and its gene expression in peach fruit. Further the results indicate that CO₂ and 1-MCP regulate ethylene biosynthesis in peach fruit during ripening, at least in part, by antagonizing ethylene action.

Key words: ACC oxidase, carbon dioxide, ehylene, 1-methylcyclopropene, peach, Prunus persica.