Studies on the biosynthesis of isocoumarins in carrot root tissues : induction by substances other than ethylene and effects of metabolic inhibitors.
Ethylene has been shown to induce carrot tissues to synthesize 8-hydroxy-6-methoxy-3-methyl-3,4-dihydroisocoumarin and 5-hydroxy-7-methoxy-2-methylchromone or eugenin. Our present data showed that the induction of isocoumarin formation could also be obtained by treating carrot slices with dinitrophenol and methylene blue. Methylene blue enhanced ethylene production, but dinitrophenol did not, therefore the action of the latter could not be mediated by ethylene. Arsenite inhibited isocoumarin synthesis, indicating the involvement of the glycolysis pathway. Assays on the pattern of derivation of isocoumarin from glucose lent support to the idea that isocoumarin is formed predominantly through the Embden-Meyerhof-Parnas pathway. Dinitrophenol-induced enhancement of both respiratory activity and isocoumarin formation indicates that the operation of the Krebs cycle and subsequently of the electron transport chain oxidations is required to provide acetate, the precursor of isocourmarin, as well as the energy necessary for the synthesizing process. The long initial lag phase as well as the mode of inhibition by cycloheximide seem to indicate that the ethylene-induced synthesis of isocoumarin is a sequential process.
D001151:Arsenic / Q000494:pharmacology; D002245:Carbon Dioxide / Q000378:metabolism; D003374:Coumarins / Q000096:biosynthesis*; D003513:Cycloheximide / Q000494:pharmacology; D004140:Dinitrophenols / Q000494:pharmacology*; D005030:Ethylenes / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D008751:Methylene Blue / Q000494:pharmacology*; D010101:Oxygen Consumption; D010944:Plants / Q000187:drug effects / Q000378:metabolism*
D003374:Coumarins; D004140:Dinitrophenols; D005030:Ethylenes; D002245:Carbon Dioxide; D003513:Cycloheximide; D005947:Glucose; D001151:Arsenic; D008751:Methylene Blue