An Antisense Gene Stimulates Ethylene Hormone Production during Tomato Fruit Ripening.

The ripening of many fruits is controlled by an increase in ethylene hormone concentration. E8 is a fruit ripening protein that is related to the enzyme that catalyzes the last step in the ethylene biosynthesis pathway, 1-aminocyclopropane-1-carboxylic (ACC) oxidase. To determine the function of E8, we have transformed tomato plants with an E8 antisense gene. We show here that the antisense gene inhibits the accumulation of E8 protein during ripening. Whereas others have shown that reduction of ACC oxidase results in reduced levels of ethylene biosynthesis, we find that reduction of the related E8 protein produces the opposite effect, an increase in ethylene evolution specifically during the ripening of detached fruit. Thus, E8 has a negative effect on ethylene production in fruit.