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Arabinogalactan-proteins are glycoproteins that occur in higher plants and are involved in important processes like cell differentiation and plant growth. In the medicinal plant Echinacea purpurea L., they belong to the putative immunomodulating compounds and are structurally well characterized. For microscopic localization of arabinogalactan-proteins, synthetic (β-D-Glc)3 Yariv phenylglycoside that specifically binds to most plant arabinogalactan-proteins was used to label arabinogalactan-proteins in fresh cut sections of stems and petioles of Echinacea purpurea. Polyclonal antibodies against (β-D-Glc)3 Yariv phenylglycoside were used to detect the arabinogalactan-protein-(β-D-Glc)3 Yariv phenylglycoside complex. After addition of fluorescein isothiocyanate-conjugated secondary antibodies, the sections were analyzed by confocal laser scanning microscopy. Arabinogalactan-proteins are localized mainly in the central cylinder in the collateral vascular bundles, especially in the area of the xylem. In cell walls of fully differentiated vessels and tracheids, arabinogalactan-proteins have been detected mainly at the inner area of the wall close to the cell lumina. Intense labeling occurs around pit canals connecting adjacent vessels. Furthermore, arabinogalactan-proteins are present in the lumina of cells of the sclerenchyma caps and in companion cells of the phloem., (Georg Thieme Verlag KG Stuttgart · New York.)

From the high molecular weight fraction of an aqueous extract from roots of Echinacea purpurea L. Moench, arabinogalactan-proteins (AGPs), a class of proteoglycans proposed to be involved in cell differentiation and plant growth, were purified and characterized with regard to amino acid composition and structure of the polysaccharide moiety. The protein content of the AGP was 5.0 % (w/w) with the dominating amino acids Glx, Hyp, Asx, Ser, Thr and Ala. The highly branched polysaccharide moiety shows a linkage composition typical of AGPs with 1,3-, 1,6- and 1,3,6-linked galactopyranosyl residues and arabinofuranosyl residues predominantly as terminal and 1,5-linked residues. Terminal units of glucuronopyranose acid were also detected. Furthermore, a new method for the localization of AGPs in plant tissue has been developed. The synthetic (beta- D-Glc)(3) Yariv phenylgycoside (betaGlcY) is known to specifically bind to AGPs. For immunolocalization, polyclonal betaGlcY-antibodies have been generated and were used to label Yariv-treated thin sections of roots from E. purpurea. After addition of the FITC-conjugated secondary antibody, the sections were analyzed by confocal laser scanning microscopy. AGPs are detected mainly in the central cylinder in the area of the xylem. Cell walls of vessels and tracheids are strongly labelled, especially at the inner area of the wall. Furthermore, there is intense labelling of the pit canals., (Georg Thieme Verlag KG Stuttgart, New York.)