Varietal Differences in the Potential to Produce Ethylene and Gene Expression of ACC Synthase and ACC Oxidase between 'Kui mi' and 'Hong xin' of Chinese Kiwifruit.

Abstract

Large varietal differences in ethylene production in Chinese kiwifruits were found, especially between 'Kui mi' and 'Hong xin', based on the sensitivity and responsiveness of the cultivars to exogenous ethylene, which could induce autocatalytic ethylene production in fruit. The difference in the potential to induce ethylene production is attributed to the greater gene expression of ACC synthase in 'Kui mi' than in 'Hong xin'. In contrast, no distinct differences were found in the transcript levels of ACC oxidase gene between these cultivars. 'Kui mi' having a high rate of ethylene production also had a high ACC content compared with 'Hong xin'. When endogenous ethylene production reached a peak at 96 hr after 24 hr-ethylene treatment, the transcript levels of ACC synthase gene were most prominent. However, the transcript level of ACC oxidase gene was clearly detected in all samples of 0 hr and more after a 24 hr-ethylene treatment. These results suggest that a key enzyme which controls the rate of endogenous ethylene production in kiwifruit is ACC synthase, not ACC oxidase.