Posthanfest zyxwvutsrqpo =WYN zyxwvutsrqpon Technology Postharvest Biology and Technology 5 (1995) 51-65 Induction of ethylene biosynthesis and polyamine accumulation in cucumber fruit in response to carbon dioxide stress Francis M. Mathooko *, Yasutaka Kubo, Akitsugu Inaba, Reinosuke Nakamura Laboratory zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA of Postharvest Horticulture, Faculty of Agriculture, Okayama University, Tstrshima, Okayama 700, Japan Accepted 12 January 1994 zyxwvutsrqponmlkjihgfedcbaZYXWV Abstract Carbon dioxide stress-induced ethylene biosynthesis, respiration and polyamine accumu- lation in cucumber fruit (Cucumti sutivus L. cv. Sharp-l) held at 25°C was investigated. Control fruit produced little ethylene and the respiration rate decreased with increase in incubation time while polyamine levels decreased. Elevated CO2 induced ethylene produc- tion, respiration and polyamine accumulation. Putrescine and spermidine levels increased in response to COz treatment, whereas spermine levels were not significantly affected. No cadaverine was detected in all treatments. The increase in ethylene production paralleled increases in 1-aminocyclopropane-1-carboxylic acid (ACC) and the activities of both ACC synthase and in vitro ACC oxidase. Infiltration of the fruit with aminooyacetic acid, a potent inhibitor of the conversion of S-adenosylmethionine (AdoMet) to ACC completely blocked COz stress-induced ethylene production. Similarly, cycloheximide, an inhibitor of nucleocytoplasmic protein synthesis effectively blocked CO2 stress induction of polyamine accumulation, ethylene production, ACC formation and the development of ACC synthase. Withdrawal of CO* gas caused cessation of increases in ethylene production, respiration, ACC, putrescine and the activities of ACC synthase and ACC oxidase, but caused increase in spermidine and spermine levels. These data indicate that CO2 induces de novo synthesis of ACC synthase thereby causing accumulation of ACC and increase in ethylene production and suggest that the conversion of AdoMet to ACC is the rate-limiting step in CO2 stress-induced ethylene biosynthesis. The induction, however, requires continuous presence of the stimulus. The results also suggest that protein synthesis might be required for the CO:! stress induction of polyamine * Corresponding author. Fax: 81 (86) 254-0714. Abbreviations: ACC, 1-aminocyclopropane-1-carboxylic acid; ADC, arginine decarboxylase; AdoMet, S-adenosylmethionine; AOA, aminooxyacetic acid; CHI, cycloheximide; CS, carbon dioxide stress; GC, gas chromatograph. 0925-5214/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved. SSDI0925-5214(94)00003-B