Plant defence responses in isonicotinamide-treated tobacco cells. Evidence supporting a role for nicotinamide related metabolites as stress mediators in plant defense metabolism

Isonicotinamide-induced defense responses in tobacco cells were investigated. Isonicotinamide (IND) induced the activity of phenylalanine ammonia-lyase and the accumulation of phenolics and sesquiterpenoids. Pre-treatment of cells with IND, followed by secondary elicitation with chitosan or an elicitor from Phytophthora nicotianae, resulted in elevated levels of phenolics and solavetivone. HPLC and GC analyses revealed changed phenolic and sesquiterpenoid profiles following secondary elicitation, indicating a conditioning effect for IND. Rapid phosphorylation of several proteins in IND-conditioned cells elicited with both chitosan and the fungal elicitor were also revealed. IND appears to act as a modulator in the coordination of defense responses.