A 3'-end truncated crystal protein gene derived from Bacillus thuringiensis subsp. aizawai 7.29, encoding the toxic fragment of the insecticidal CRYIC protein, was placed under the control of the CaMV 35S promoter with a duplicated enhancer. Its expression in tobacco conferred significant insecticidal activity towards the important pest Spodoptera littoralis. Expression of the CRYIC toxin is at its maximum level at the early stages of plant development then decreases as the plants become older.