Relation between ethylene-producing potential and gene expression of 1-aminocyclopropane-1-carboxylic acid synthase in Actinidia chinensis and A. deliciosa fruits

Large differences in gene expression of 1-aminocyclopropane-1-carboxylic ac id (ACC) synthase, ACC contents, and ACC synthase activitiy were found in d ifferent tissues of fruit between members of two kiwifruit species, (cv) Ac tinidia chinensis ('Kui mi') and A. deliciosa: ('Hayward'). ACC synthase mR NA accumulated mostly in the outer pericarp, slightly in the inner pericarp , and in a trace quantity in the columella of 'Hayward' fruit that produces much less ethylene than does 'Kui mi'. However, gene transcripts at signif icant levels exist in all sections of 'Kui mi' fruit which reflects a large potential to produce ethylene. ACC levels and ACC synthase activities were much higher in all the tissues of 'Kui mi' fruit than in 'Hayward' fruit, which indicates that these enzymes are the primary cause for the varietal d ifference in the ability to produce ethylene in kiwifruit.