Abstract: A method for synthesizing a protein of interest within a plant or a portion of a plant is provided. The method involves introducing one or more than one nucleic acid sequence encoding a protein of interest operatively linked with a regulatory region obtained from a photosynthetic gene that is active in the plant, in a transient manner. The plant is then maintained under conditions that permit the nucleic acid sequence encoding the protein of interest to be expressed in the plant or the portion of the plant. The plant may be pruned prior to the introducing one or more than one nucleic acid sequence.