Expression and activity of cell-wall-degrading enzymes in the latex of opium poppy, Papaver somniferum L.

Abstract

The alkaloid-rich latex of the opium poppy, Papaver somniferum L., is valued as a source of pharmaceuticals including thebaine, codeine, and morphine, but is also harvested for heroin production. The poppy laticifer system develops through the gradual disappearance of the common walls between differentiating laticifer elements throughout the plant. Gene homologues for cell-wall-degrading enzymes were found during random sequencing of an opium poppy latex cDNA library. RNA gel blot analysis of cellulase, polygalacturonase beta-subunit, 1,3-beta-glucanase, and xyloglucan endotransglycosylase homologues showed their expression was not limited to laticifers. In contrast, poppy gene homologues to pectin methylesterase (PME), pectin acetylesterase (PAE) and pectate lyase (PL) where all highly expressed and latex-specific. Enzyme assays confirmed the presence of PME, PAE, and PL activities in latex serum. The abundance of transcripts encoding pectin-degrading enzymes in latex suggests that these enzymes may play an important role in laticifer development.