Reinosuke Nakamura

Induction of ethylene biosynthesis and polyamine accumulation in cucumber fruit in response to carbon dioxide stress

Abstract Carbon dioxide stress-induced ethylene biosynthesis, respiration and polyamine accumulation in cucumber fruit ( Cucumis sativus L. cv. Sharp-1) 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 CO 2 induced ethylene production, respiration and polyamine accumulation. Putrescine and spermidine levels increased in response to CO 2 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 aminooxyacetic acid, a potent inhibitor of the conversion of S-adenosylmethionine (AdoMet) to ACC completely blocked CO 2 stress-induced ethylene production. Similarly, cycloheximide, an inhibitor of nucleocytoplasmic protein synthesis effectively blocked CO 2 stress induction of polyamine accumulation, ethylene production, ACC formation and the development of ACC synthase. Withdrawal of CO 2 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 CO 2 induces de navo 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 CO 2 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 2 stress induction of polyamine biosynthesis. The results further suggest that in cucumber fruit under CO 2 stress, at least, the ethylene and polyamine biosynthetic pathways are not competitive.

Postharvest ripening and ethylene biosynthesis in purple passion fruit

Abstract A study was undertaken to investigate the pattern of changes in some chemical constituents, ethylene biosynthesis, and the effect of ethylene treatment during postharvest ripening in purple passion fruit (Passiflora edulis Sims.). During ripening, sucrose content decreased while fructose and glucose contents increased. Citric and malic acid contents slightly increased during the early stage of ripening and decreased thereafter. Amino acids did not change significantly, except for proline, which increased rapidly towards the late stage of ripening. While 1-aminocyclopropane-1-carboxylic acid (ACC) content and ACC synthase activity increased in parallel with ethylene production, ACC oxidase activity was already high when harvested at the turning stage and further increased during ripening. Application of 1000 ppm ethylene for 24 h did not induce earlier onset of ethylene production when applied on harvest day, but was effective when applied one day or five days after harvest. The results indicate that purple passion fruit produces ethylene with the same biosynthetic pathway as other tissues in higher plants; its ethylene biosynthesis is regulated mainly by ACC synthase activity, and the sensitivity to ethylene might have changed after harvest as the fruit ripened.

Characterization of the regulation of ethylene biosynthesis in tomato fruit by carbon dioxide and diazocyclopentadiene

Abstract The regulation of ethylene biosynthesis by CO2 and diazocyclopentadiene (DACP), both inhibitors of ethylene action, was investigated in tomato (Lycopersicon esculentum Mill. cv. ‘Momotaro’) fruit held at 25 °C. When the tomato fruit at the pink stage of ripeness were treated with 20% CO2 (+ 20% O2 + 60% N2) or DACP, ethylene production by the fruit was rapidly decreased. The inhibition of ethylene production resulted primarily, if not solely, from the suppression of the activities of both 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase. The inhibition of ACC synthase activity subsequently led to low levels of ACC. CO2 treatment further inhibited ACC conjugation into 1-(malonylamino) cyclopropane-1-carboxylic acid (MACC). By contrast, DACP-treated fruit maintained slightly higher levels of MACC relative to the control fruit. When the fruit were transferred from the CO2-enriched atmosphere to air, ethylene production, ACC and MACC contents and the activities of ACC synthase and ACC oxidase increased gradually to the control level after 24 h, while these values, except for MACC content, remained low in DACP-treated fruit throughout the experimental period. These results indicate that CO2 and DACP regulate ethylene production in tomato fruit by inhibiting ACC synthase and ACC oxidase activities and further support the hypothesis that the autocatalytic signal associated with ethylene action during fruit ripening stimulates the activities of both enzymes.

Regulation by carbon dioxide of wound-induced ethylene biosynthesis in tomato pericarp and winter squash mesocarp tissues

Abstract The effects of CO 2 treatment on wound-induced ethylene biosynthesis were investigated in excised pericarp and mesocarp tissues of tomato ( Lycopersicon esculentum Mill. cv. TVR-II) and winter squash ( Cucurbita maxima Duch. cv. Ebisu) respectively. Wounding caused increase in ethylene production rate, the levels of 1-aminocyclopropane-1-carboxylic acid (ACC) and 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC) and the activities of ACC synthase and ACC oxidase. The increase in the rate of ethylene production and ACC synthase activity were suppressed by CO 2 treatment and was dependent on CO 2 concentration. CO 2 treatment also suppressed wound-induced increase in ACC level irrespective of the CO 2 concentration. The presence of 10% CO 2 had no effect on ACC conjugation to MACC induced by wounding while 60% CO 2 suppressed almost completely ACC conjugation. CO 2 promoted and inhibited induction of ACC oxidase activity in excised tomato and winter squash tissues respectively. These results suggest that CO 2 inhibits wound-induced ethylene biosynthesis by reducing the availability of ACC through repression of ACC synthase synthesis and/or inhibition of its activity. Also endogenous ethylene produced in response to wounding may play a role in the regulation of wound-induced ethylene production.

Inhibition of auxin-induced ethylene production in cucumber fruit discs by carbon dioxide

Abstract The induction of ethylene biosynthesis by indole-3-acetic acid (IAA) and its regulation by CO 2 was examined in cucumber ( Cucumis sativus L., var. Sharp-1) fruit discs. Treatment of discs with IAA significantly stimulated ethylene production and the extent depended on IAA concentration upto 1 mM. The increase in IAA-induced ethylene production was accompanied by increase in the activities of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase (also known as ethylene-forming enzyme) and a massive accumulation of ACC and 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC). The induction of ethylene production by IAA was inhibited by treatment with CO 2 . The extent of inhibition was dependent upon the concentration of CO 2 . Carbon dioxide inhibited IAA-induced ethylene biosynthesis by suppressing ACC synthase and ACC oxidase activities. Additionally, CO 2 inhibited ACC conjugation into MACC. The results indicate that inhibition of ethylene production by CO 2 in cucumber fruit discs following IAA treatment is due to inhibition of both ACC synthesis and ACC oxidation.