Abstract
In coffee plants, caffeine is synthesized through sequential three-step methylation of xanthine derivatives: first, xanthosine into 7-methyl xanthine, then into 3,7-dimethyl xanthine (theobromine), and finally into 1,3,7-trimethyl xanthine (caffeine). Using previously isolated cDNA encoding theobromine synthase (CaMXMT), we produced transgenic lines, in which expression of CaMXMT was expected to be supressed by RNAi method. Embryogenic calli of coffee were co-cultured with Agrobacterium tumefaciens EHA101 harboring pIG121-Hm, containing the gene-specific RNAi sequences. Expression of CaMXMT investigated by RT-PCR was obviously suppressed by RNAi constructs. Consequently, endogenous level of caffeine in the transformed cells was reduced to less than one tenth level in comparison with that in non-transformed cells.
