PLANT PHYSIOLOGY , Vol 102, Issue 3 911-916, Copyright © 1993 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Ripening Physiology of Fruit from Transgenic Tomato (Lycopersicon esculentum) Plants with Reduced Ethylene Synthesis
H. J. Klee
Monsanto Company, Chesterfield, Missouri 63198
The physiological effects of reduced ethylene synthesis in a transgenic
tomato (Lycopersicon esculentum) line expressing
1-aminocyclopropane-1-carboxylic acid (ACC) deaminase enzyme have been
examined. Fruit from the transgenic line 5673 ripen significantly slower
than control fruit when removed from the vine early in ripening. In
contrast, fruit that remain attached to the plants ripen much more rapidly,
exhibiting little delay relative to the control. Ethylene determinations on
attached fruit revealed that there was significantly more internal ethylene
in attached than detached fruit. The higher ethylene content can fully
account for the observed faster on-the-vine ripening. All of the data are
consistent with a catalytic role for ethylene in promoting many, although
not all, aspects of fruit ripening. Biochemical analyses of transgenic
fruit indicated no significant differences from controls in the levels of
ACC oxidase or polygalacturonase. Because transgenic fruit are
significantly firmer than controls, this last result indicates that other
enzymes may have a significant role in fruit softening.
