Identification and Characterization of Latex-Specific Proteins in Opium Poppy

Abstract

ABSTRACFLatex from the opium poppy, Papaver somniferum L., was analyzed by polyacrylamide gel electrophoresis (PAGE). Two latex-specific bands were identified in protein samples of poppy latex using one-dimensional native PAGE. Second dimension analysis with SDS-PAGE indicates that these proteins have a relative molecular weight of approximately 20 kilodaltons. We have termed these polypeptides the major latex proteins (MLPs). Polyclonal antibodies prepared against the MLPs were used to probe protein gel blots of latex and poppy tissues known to lack laticifers.Laticifer-free tissues showed no reaction with anti-MLP immunoglobulin G indicating that MLPs are found only in poppy latex. MLP distribution was also examined in mature opium poppy tissues by immunocytochemistry. Laticifers were differentially labeled by fluorescein isothiocyanate secondary labeling of anti-MLP immunoglobulin G and could easily be identified in both transverse and longitudinal section. Fractionation studies of isolated latex showed that MLPs are concentrated in the latex cytosol and not in alkaloidal vesicles. Analysis of latex proteins by conventional two-dimensional electrophoresis indicates that the two MLP bands are composed of several distinct polypeptides with similar relative molecular weights. The pIs of these molecules range from 6.0 to 3.5. The role(s) of MLPs in laticifer metabolism has not been determined.

Phloem-Specific Expression of Tyrosine/Dopa Decarboxylase Genes and the Biosynthesis of Isoquinoline Alkaloids in Opium Poppy.

“…In aerial organs, the alkaloids are contained within the vesicle-rich cytoplasm of mature laticifers (Fairbairn and Djote, 1970;Fairbairn et al, 1974;Roberts et al, 1983;Nessler et al, 1985;Rush et al, 1985). Latex collected from unripe seed capsules (Figure 4, stage 6), stems, or young leaves exhibited a profile of extractable alkaloids that was both quantitatively and qualitatively similar, as shown in Figure 6.…”

Proteomic Identification of Putative MicroRNA394 Target Genes in Arabidopsis thaliana Identifies Major Latex Protein Family Members Critical for Normal Development

“…Members of the second group of MS-identified putative LCR target proteins, the MLP protein family, were first identified in opium poppy (Papaver somniferum) as latex-specific polypeptides (57), and have because been found to be highly conserved in plants (58,59). Although the Arabidopsis MLP protein family consists of twenty-four members (58,59), only peptides derived from family member MLP28 showed differential accumulation in LCR-OE and LCR-KD plants by LC-MS/MS.…”

Norcoclaurine Synthase Is a Member of the Pathogenesis-Related 10/Bet v1 Protein Family

“…Mouse NCS and 6OMT antisera (Samanani et al, 2006) and rabbit opium poppy MLP antiserum (Nessler et al, 1985) were used for immunocytochemical localization. Tissue sections were blocked for 1 h in Trisbuffered saline (TBS; 10 mM Tris-HCl, pH 7.2, 500 mM NaCl, 0.3% [v/v] Tween 20 containing 1% [w/v] BSA [Fraction V; Roche Diagnostics]), incubated with the primary antibody for 3 h in a humid chamber, and rinsed five times for 15 min each in TBS containing 1% (w/v) BSA.…”