RÉSUMÉ
For expression of foreign genes in plant, plant virus vector provides many advantages, such as high expression level, short expression period and wider plant hosts. In the present study, we report the expression of thymosin alpha 1 (Talpha1) in tomato fruits by potato virus X (PVX) vector. Talpha1 gene fragment from plasmid pGEM-T containing Talpha1 gene was cloned into plant virus vector pGR107 and the resulting pGR107-Talpha1 plasmid was confirmed by digestion with Sal I and Cla I. To express the Talpha1 protein, Agrobacterium tumefaciens GV3101 transformed with pGR107-Talpha1 was directly injected into tomato fruits through the fruit stylar apex at different developmental stages. The ELISA results showed that Talpha1 protein was expressed successfully in fruits, and the highest expression level was obtained from 2.5-3 week-old tomato fruits inoculated by bacterium at 1.0 OD600 density.