Functional expression of miraculin, a taste-modifying protein, in Transgenic Miyagawa Wase Satsuma mandarin (Citrus unshiu Marc.)

Miraculin is a taste modifying plant protein, which displays a peculiar property of being able to modify sour taste into sweet taste. Thus, there has been an increasing interest in miraculin due to this amazing property. In the present study, miraculin gene was introduced into the Miyagawa Wase Satsuma mandarin (Citrus unshiu Marc.) callus by Agrobacterum-mediated transformation to produce a citrus transgenic plant and express the recombinant miraculin protein under the control of 35S promoter. Satsuma mandarin is one of the choicest citrus varieties grown widely and commercially in Korea, especially in Jeju Island, and Japan. Expression of this protein in the transgenic plant resulted in the accumulation of a significant amount of the miraculin protein in the leaves. To investigate whether the expressed protein was correctly modified, the dimerization and N-glycosylation of recombinant miraculin in the transgenic plants were analyzed. The recombinant protein also showed a sufficient biological activity. These results open up a new way of expression system in woody plants such as citrus and can provide a suitable alternative for producing recombinant miraculin.