Pj. Facchini, TEMPORAL CORRELATION OF TYRAMINE METABOLISM WITH ALKALOID AND AMIDE BIOSYNTHESIS IN ELICITED OPIUM POPPY CELL-CULTURES, Phytochemistry, 49(2), 1998, pp. 481-490
Aromatic amines are involved in the biosynthesis of many plant seconda
ry metabolites, including benzylisoquinoline alkaloids and hydroxycinn
amic acid amides. Incorporation of tyramine and dopamine into both the
antibiotic alkaloid sanguinarine and hydroxycinnamic acid amides was
shown to occur in elicitor-treated opium poppy cell cultures. A tempor
al correlation was demonstrated between the biosynthesis of alkaloids
and amides, the accumulation of tyrosine/dopa decarboxylase (TYDC) and
berberine bridge enzyme (BBE) mRNAs, and the induction of tyramine hy
droxycinnamoyl transferase (THT) activity. The induction of TYDC mRNAs
occurred most rapidly, whereas the subsequent activation of BBE mRNAs
and THT activity correlated with the synthesis and accumulation of sa
nguinarine and amides, respectively. In pulse-labeling experiments, a
maximum of 1.2 and 0.6% of exogenous C-14-tyramine and C-14-dopamine,
respectively, was incorporated into sanguinarine after elicitor treatm
ent of cell cultures. In contrast, a maximum of 24 and 35% of exogenou
s 14C-tyramine and C-14-dopamine, respectively, was incorporated into
an acid-insoluble fraction of the cell wall after elicitor treatment.
Insolubilized radioactivity was released from cell walls after hydroly
tic extraction and recovered mostly as hydroxycinnamic acid amides and
free amines. The elicitor-induced incorporation of C-14-amines into b
oth sanguinarine and cell walls decreased during the cell culture grow
th cycle. The prolonged induction of THT activity in elicited cultures
, coupled with high and constitutive peroxidase activity, suggests tha
t the observed decrease in cell wall labeling 5h after the addition of
elicitor was due to hydroxycinnamoyl-CoA or H2O2 limitation. (C) 1998
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