Wound-Induced Ethylene Production and 1-Aminocyclopropane-1-carboxylic Acid Synthase in Mesocarp Tissue of Winter Squash Fruit

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Discs (9 mm in diameter and 2 mm in thickness) sliced from mesocarp of winter squash fruit (Cucurbita maxima Duch.) upon incubation at 24℃ produced ethylene at an increasing rate after a lag period of 3 h. 1-Aminocyclopropane-1-carboxylic acid (ACC) synthase activity also increased at a rapid rate after lag period of less than 3 h, reaching a peak 14h after incubation and then declining sharply. The rise in ACC synthase activity preceded a rapid increase in ACC formation and ethylene production. Induction of ACC synthase by wounding in sliced discs was strongly suppressed by the application of cycloheximide, actinomycin D and cordycepin, suggesting that the rise in ACC synthase activity may result from de novo synthesis of protein. ACC synthase extracted from wounded tissue of winter squash mesocarp required pyridoxal phosphate for its maximum activity. The optimum pH of the reaction was 8.5. K_m value for S-adenosylmethionine was 120 μM. The reaction was markedly inhibited by aminoethoxyvinylglycine with K_i value being 2.7 μM.
日本植物生理学会の論文