Chitin-induced biosynthesis of phytoalexin 4' -deoxyaurone in cell suspension cultures of 'old man' cactus, Cephalocereus senilis

Cell suspension cultures of Cephalocereus senilis develop red pigmentation when infected by fungus. Previous work in our laboratory has established that chitin, a fungal cell wall component, can elicit the same response. These elicited cell cultures also produce several unusual flavonoids lacking the normal 4'-hydroxyl substitution in the B-ring, including the red pigment cephalocerone, a 4'-deoxyaurone. Previous enzymological studies showed that the elicited cell suspension cultures have the necessary enzymatic activities required for the conversion of L-phenylalanine to the 4'-deoxyflavonoids. Explanations for the 4'-deoxyflavonoid biosynthesis include (1) a bypass of cinnamic acid 4-hydroxylase therefore leading to an accumulation of 4'-deoxy precursors available for the 4' -deoxyflavonoid production and (2) a dehydroxylation step within the flavonoid biosynthetic pathway.; The current biochemical investigations into the biosynthesis of the phytoalexin cephalocerone using HPLC metabolic profiling of isotope dilution experiments established the existence of a novel 4'-dehydroxylation step instead of a 4'-hydroxyl "bypass". Our results strongly suggest that the metabolic flux involved in the selective production of 4'-deoxyflavonoids may be controlled by a specific enzyme activity that dehydroxylates the 4'-position of the tetrahydroxychalcone B-ring.