Production of the taste-modifying protein, miraculin, in transgenic lettuce

Richadella dulcifica, a native shrub in tropical West Africa, gives red berries that have the unusual property of modifying a sour taste into a sweet taste. The red berries contain a taste-modifying protein named miraculin. A synthetic gene encoding miraculin was placed under the control of constitutive promoters and transferred to lettuce. High expression of miraculin was obtained, with accumulation of up to 1% total soluble protein in lettuce leaf. In addition, the miraculin expressed in lettuce possesses a taste-modifying activity.