Effect of Ethylene Treatment on Ethylene Biosynthetic Pathyway in Immature Tomato Fruit

Abstract

This study was conducted to understand the regulatory mechanism of ethylene biosynthesis in developing and ripening tomato fruit. The ethylene biosynthetic pathway in immature and ripening tomato fruit treated with ethylene was observed by analyzing the intermediate and enzyme activities. Internal ethylene concentration was low in developing stages of tomato fruit, began to increase in the mature green, and increased sharply in the ripening stage. Carbon dioxide production in immature and mature green fruit was stimulated with 100, μl·l^-1 of ethylene treatment for 22 hr, but ethylene production was not enhanced. Activities of ACC oxidase and ACC malonyltransferase were stimulated with ethylene treatment and the ACC oxidase activity of immature fruit was similar to that at the ripening stage, whereas ACC malonyltransferase activity of immature fruit was substantially greater than in the ripening stage. In mature green tomato fruit, ACC oxidase and ACC malonyltransferase reached maximum rate after one day of ethylene treatment and remained at about the same rate with continual treatment. However, the rate dropped sharply when the fruit were transferred to air. ACC synthase activity and ACC content of immature green fruit did not change during the two days of ethylene treatment but increased when transferred to air for two days.