Regulation mechanisms of phenolic production in the lichen Himantormia lugubris, as deduced from the analysis of metabolite accumulation

Abstract

HPLC analysis of the phenolic fraction of the lichen Himantormia lugubris reveals that atranorin, barbatolic acid and methyl β- orcinol carboxylate are mainly accumulated in the thallus. Samples floated in the dark on acetate actively synthesize barbatolic acid from the beginning of the incubation, and atranorin after an initial loss during the first hour of incubation. The amount of the atranorin precursor, methyl β-orcinol carboxylate, remains unchanged after an initial decrease similar to that found for atranorin. Active production of both atranorin and barbatolic acid is inhibited by white light and recovered by adding 3-(3′-dichlorophenyl)-1,1-dimethylurea (DCMU) or ATP to the incubation media. The supply of exogenous ATP strongly activates the accumulation of methyl β-orcinol carboxylate. This possibly indicates that ATP behaves as a limiting factor for the steps catalyzed by acetyl-CoA carboxylase and methionine adenosyltransferase, related to the production of this last phenolic. A glucose supply in the dark assures the ability of lichen thalli for phenolic synthesis whereas this process is strongly decreased by exogenous cyclic AMP.