Related Experiment Video
Updated: May 6, 2026

Phloem Sap Sampling from Brassica napus for 3D-PAGE of Protein and Ribonucleoprotein Complexes
Published on: January 9, 2018
A phloem-specific, lectin-like protein is located in pine sieve-element plastids by immunocytochemistry
A Schulz1, M C Alosi, D D Sabnis
1Zellenlehre der Universität Heidelberg, Im Neuenheimer Feld 230, D-6900, Heidelberg, Germany.
Abstract:
Two co-purifying phloem polypeptides of 24 and 25 kilodaltons (kDa) were isolated from homogenates of Pinus sabiniana Dougl. phloem by differential centrifugation, selective solubilization and electrophoresis, and rabbit antibodies raised against them. The antisera were found to be specific for doublet bands between 23 and 25 kDa in Western blots of whole phloem extracts of Pinus species; no xylem polypeptides were labelled, nor did labelling occur in blots of phloem extracts from other genera in the Pinaceae. Solubilized phloem polypeptides bind strongly to chitin (oligomeric N-acetylglucosamine) columns and are sensitive to thiol reagents, both characteristics which relate them to phloemspecific lectins isolated from angiosperm species (C. Allen, 1979, Biochem. J. 183, 133-137; A.K. Gietl et al., 1979, Planta 144, 367-371). Fluorescence microscopy and immuno-gold electron microscopic cytochemistry demonstrated antigenic sites specifically associated with protein crystals peculiar to the sieve-element plastids of the Pinaceae.
Related Concept Videos
Phloem and Sugar Transport
Phosphoinositides and PIPs
Different phosphoinositides are synthesized and recruited on the cytosolic face of the plasma membrane. The localization of specific phosphoinositides concentrated in separate membrane...
Protein Transport to the Inner Chloroplast Membrane
Protein Transport to the Outer Chloroplast Membrane
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
Protein Transport to the Stroma
Protein complexes called the translocon of the outer chloroplast membrane or TOC complex, and the translocon of the inner chloroplast membrane or TIC complex mediate the...

