Induction of phenylpropanoid and tyramine metabolism in pectinase‐ or pronase‐elicited cell suspension cultures of tobacco (Nicotiana tabacum)

Abstract

The induction of the phenylpropanoid pathway and of tyramine metabolism was monitored in cell suspension cultures of Nicotiana tabacum treated with cell wall‐degrading enzymes, in an attempt to correlate the synthesis of hydroxycinnamic acid amides of tyramine with the formation of wall‐bound phenolic polymers. Treatment with commercial pectinase (from Penicilium occitanis) induced a rapid rise in phenylalanine ammonia‐lyase (EC 4.3.1.5), 4‐coumarate:CoA ligase (EC 6.2.1.12), tyramine hydroxycinnamoyltransferase (EC 2.3.1.110) and peroxidase (EC 1.11.1.7) activities, and a concomitant decline in cinnamyl alcohol dehydrogenase (EC 1.1.1.195) activity. The induction of the phenylpropanoid pathway and of the synthesis of cinnamoyl‐tyramines preceded the death of a large proportion of the elicited cells. When the cultures were treated with pronase (from Streptomyces griseus), most cells remained alive and the induction of enzymes of the phenylpropanoid pathway lasted for several days, resulting in an accumulation of cinnamoyltyramines in the cells and in the culture medium. Treatment with pronase induced an increase in the activity of moderately anionic isoperoxidases which were also induced in pectinase‐treated cells. Cinnamyl alcohol dehydrogenase activity remained stable in pronase‐elicited cells, which rapidly accumulated thioglycolic acid‐extractable phenolic polymers in their cell walls. The accumulation of these polymers coincided with the induction of 4‐coumarate:CoA ligase but preceded the rise in tyramine hydroxycinnamoyltransferase and peroxidase activities.