Regulation of ethylene and polyamine synthesis by elevated carbon dioxide in cherimoya fruit stored at ripening and chilling temperatures

Abstract

In this study we focused on the effect of high CO₂ level (20%) on ethylene and polyamine biosynthesis in cherimoya (Annona cherimola Mill.) fruits stored at ripening (20˚C) and chilling (6˚C) temperatures. At ripening temperature, CO₂ inhibited ethylene production, but 1-aminocyclopropane-1- carboxylate (ACC) oxidase activity was similar to that in ripe control fruits. CO₂ treatment led to a decline in putrescine (Put) and a major accumulation of spermidine (Spd) and spermine (Spm) without any effect on arginine decarboxylase (ADC) activity. These results confirm the preferential transformation of Put to Spd and Spm in CO₂ -treated fruits. At chilling temperature, the increase in ACC oxidase activity was inhibited and the V_max of ADC increased. A combination of chilling temperature storage and high CO₂ level led to suppression of basal ethylene production while ACC oxidase activity remained unchanged. In addition, fruits held at these conditions had higher polyamine titres than the untreated control. We propose that, in CO₂ -treated fruits, the absence of autocatalytic or basal ethylene production, depending on the temperature, may be due to deviation of the S-adenosylmethionine (SAM) pool towards polyamine synthesis, primarily Spd and Spm.