Tobacco (Nicotiana tabacum L. cv. SR1) plants that were aseptically grown from seeds for about 1 month were transformed via an A. tumefaciens-mediated leaf disc procedure [20], and selected using a medium containing 30 mg l21 hygromycin. After rooting and acclimatization, the regenerated plants were grown in a closed greenhouse to set seeds. Sixteen lines of transgenic T1 seeds were tested for germination on 1/2 Murashige and Skoog medium supplemented with 30 mg l21 hygromycin. T2 seeds harvested from each T1 individual plant that showed ca. 3:1 segregation ratio were tested for hygromycin- resistance again. Finally, four homozygous T2 plant lines were used in further assays.