Expression of Curculin, a New Type of Alternative Sweetener in Transgenic Rice

Sweet tasting and taste modifying proteins are the natural alternative to flavor enhancers and artificial sweeteners. Curculin is a unique protein, which has both sweet tasting and taste modifying properties. In this study, pinII Ti plasmid vector was constructed with curculin gene, where the gene encoding curculin protein was placed under the control of the duel cauliflower mosaic virus 35S (2× CaMV 35S) promoter into rice (Oryza sativa L. var. Japonica cv. Dongjinbyeo) by Agrobacterium-mediated transformation to generate transgenic plants. Here, twenty-six plant lines were regenerated and the transgenic rice plant lines were confirmed by different molecular analysis. The genomic PCR result revealed that all of the plant lines were transgenic. The single copied and intergenic plant lines were selected by Taqman PCR analysis and FST analysis, respectively. Expression of curculin gene in transgenic rice resulted in the accumulation of curculin protein in the leave. The transgenic lines obtained in next generation, where curculin protein was also accumulated in the plant leave. Sensory analysis result suggested that the curculin protein expressing transgenic lines exerted both sweet and taste modifying activities. These results demonstrated that curculin was expressed in transgenic rice plants.