Pathogen resistance of transgenic tobacco plants producing caffeine

Caffeine is synthesized from xanthosine through three methylation steps by three independent N-methyltransferases. Using genes for these enzymes, we constructed caffeine-producing transgenic tobacco plants, which exhibited constitutive expression of disease-responsive genes and resistance against pathogen infection. Results suggested that, in addition to direct toxicity to organisms, caffeine functions as a signal molecule to activate defense systems.