IS LIPOXYGENASE INVOLVED IN POLYACETYLENE BIOSYNTHESIS IN ASTERACEAE

Polyacetylenes are a diverse group of fatty acid-derived bioactive metabolites found predominantly in the roots of Asteraceae. Stable patterns of polyacetylenes can be produced in ''hairy root'' cultures obtained by transformation with Agrobacterium rhizogenes. Bidens sulphureus ''hairy roots'' were elicited with a crude mycelial extract of Pythium aphanidermatum. Within 12 to 24 h after elicitor addition, a dramatic increase in polyacetylenes was observed. The major elicited peak was identified as a 13-carbon linear acetylene. Two lipoxygenase (LOX) were detected in B. sulphureus ''hairy roots'', showing activity peaks at pH 9.0 (LOX-1) and 6.8 (LOX-2), respectively. Lipoxygenase-l showed a transient increase in activity occuring 2 to 4 h after elicitor addition and preceding the increase in polyacetylene production. In contrast LOX-2 showed no change in activity between control and elicited root cultures. N-propyl gallate effectively inhibited LOX activity in vivo and in vitro and prevented the rise in LOX-1 activity observed in elicited root cultures. However, this inhibitor had no significant effect on the polyacetylene patterns of control or elicited roots. Thus our results suggest that lipoxygenase is not involved in polyacetylene biosynthesis.