- Expression of the gene for a small GTP binding protein in transgenic tobacco elevates endogenous cytokinin levels, abnormally induces salicylic acid in response to wounding, and increases resistance to tobacco mosaic virus infection. Sano, H., Seo, S., Orudgev, E., Youssefian, S., Ishizuka, K. Proc. Natl. Acad. Sci. U.S.A. (1994)