GENETIC ENGINEERING OF ACIDITY IN TOMATO FRUIT. I. CHARACTERIZATION OF GENES FOR NADP-MALIC ENZYME IN TOMATO FRUIT

FLAVOR IN TOMATO FRUIT IS ASSOCIATED WITH HIGH LEVELS OF BOTH SUGARS AND ACIDS. IT IS KNOWN THAT THE LEVEL OF MALIC ACID IN THE FRUIT DECLINES BY 50 PERCENT WITH FRUIT RIPENING AND THAT THIS REDUCTION IS THOUGHT TO BE MEDIATED BY A CYTOSOLIC NADP DEPENDENT MALIC ENZYME (NADP-ME). RESEARCHERS ARE ISOLATING AND CHARACTERIZING THE TOMATO NADP-ME GENES WHICH ARE EXPRESSED IN THE PERICARP DURING RIPENING BY USING A HETEROLOGOUS PROBE FOR NADP-ME FROM MAIZE. ONCE ISOLATED, THE TOMATO GENES ARE USED IN GENETIC ENGINEERING EXPERIMENTS SO THAT THE INDUCTION OF NADP-ME, WHICH OCCURS DURING RIPENING, WOULD BE REDUCED OR INHIBITED AND HIGHER MALIC ACID LEVELS WOULD PERSIST WITHIN THE RIPE FRUIT. HIGHER LEVELS OF THE SAME ENZYMES WOULD BE ENGINEERED IN THE FRUIT IN ORDER TO GAIN INSIGHT INTO MECHANISMS WHICH REGULATE ACID LEVELS IN THE FRUIT. THE ANTICIPATED OUTCOME OF THIS RESEARCH WOULD BE THE ABILITY TO DIRECTLY ENGINEER THE ACID LEVELS IN FRUIT WHICH COULD SIGNIFICANTLY AFFECT THE FLAVOR OF TOMATOES.