Control of protein activity in a plant may be obtained by modifying a protein with a CIVPS or intein. The modified protein may be less active or inactive compared to the un-modified protein, and CIVPS or intein splicing may yield the un-modified protein. The application describes transgenic plants having CIVPS or intein modified proteins capable of being expressed therein. The application relates to transgenic plants that express CIVPS (controllable intervening protein sequences) or intein modified proteins, compositions of matter comprising them, products of diverse applications made from the transgenic plants, methods to construct the transgenic plants containing CIVPS or intern modified genes, methods to express CIVPS or intein modified proteins in plants, and methods of using the transgenic plants.
