We have proposed and tested a method for characterization of the signal sequences and determinations of target protein localization in a plant cell. This method, called the AgI-PrI, implies extraction of protoplasts from plant tissues after agroinfiltration. The suggested approach combines the advantages of two widely used methods for transient gene expression in plants–agroinfiltration and transfection of isolated protoplasts. The AgI-PrI technic can be applied to other plant species.