UNCOUPLED DEFENSE GENE-EXPRESSION AND ANTIMICROBIAL ALKALOID ACCUMULATION IN ELICITED OPIUM POPPY CELL-CULTURES

Treatment of opium poppy (Papaver somniferum L.) cell cultures with au toclaved mycelial homogenates of Botrytis sp. resulted in the accumula tion of sanguinarine. Elicitor treatment also caused a rapid and trans ient induction in the activity of tyrosine/dopa decarboxylase (TYDC, E C 4.1.1.25), which catalyzes the conversion of L-tyrosine and L-dopa t o tyramine and dopamine, respectively, the first steps in sanguinarine biosynthesis. TYDC genes were differentially expressed in response to elicitor treatment. TYDC1-like mRNA levels were induced rapidly but d eclined to near baseline levels within 5 h. In contrast, TYDC2-like tr anscript levels increased more slowly but were sustained for an extend ed period. Induction of TYDC mRNAs preceded that of phenylalanine ammo nia-lyase (PAL, EC 4.3.1.5) mRNAs. An elicitor preparation from Pythiu m aphanidermatum was less effective in the induction of TYDC mRNA leve ls and alkaloid accumulation; however, both elicitors equally induced accumulation of PAL transcripts. In contrast, treatment with methyl ja smonate resulted in an induction of TYDC but not PAL mRNAs. The calmod ulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide and the protein kinase inhibitor staurosporine partially blocked the fung al elicitor-induced accumulation of sanguinarine. However, only stauro sporine and okadaic acid, an inhibitor of protein phosphatases 1 and 2 A, blocked the induction of TYDC1-like transcript levels, but they did not block the induction of TYDC2-like or PAL transcript levels. These data suggest that activation mechanisms for PAL, TYDC, and some later sanguinarine biosynthetic enzymes are uncoupled.