Stable expression and characterization of brazzein, thaumatin and miraculin genes related to sweet protein in transgenic lettuce

Abstract

Sweetener is one of the additives that makes you feel sweet. Artificial sweeteners and sugar are typical examples, and sweetness proteins with sweetness characteristics have been widely studied. These studies elucidated the transformation lettuce cells with Agrobacterium method for stable production of natural sweet proteins, brazzein, thaumatin, and miraculin. In this paper, we report use of a plant expression system for production of sweet proteins. A synthetic gene encoding sweet proteins was placed under the control of constitutive promoters and transferred to lettuce. High and genetically stable expression of sweetener was confirmed in leaves by RT-PCR and Western blot analysis. Sweet proteins expressed in transgenic lettuce had sweetnessinducing activity. Results demonstrate recombinant sweet proteins correctly processed in transgenic lettuce plants, and that this production system could be a viable alternative to production from the native plant.