Taxonomic group: plant / Streptophyta
(Phylum: Streptophyta)
NCBI PubMed ID: 7506427Journal NLM ID: 0401224Publisher: American Society of Plant Biologists
Institutions: Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder 80309-0347
Antisera raised against the major hydroxyproline-rich glycoprotein (HRGP) in carrot (Daucus carota L.) taproot, extensin-1, and a minor HRGP, extensin-2, were characterized by western blot analysis, enzyme-linked immunosorbent assay, and periodate oxidation and found to be directed against carbohydrate epitopes shared by both glycoproteins. The anti-extensin-1 antibodies (gE1) target periodate-sensitive epitopes and may recognize the terminal α-1,3-arabinoside of extensin-1. The anti-extensin-2 antibodies (gE2) recognize periodate-insensitive epitopes, possibly binding the reducing, internal β-1,2-arabinosides on the carbohydrate side chains. Despite the cross-reactivity of these antibodies, immunolocalization studies of carrot taproot and green bean (Phaseolus vulgaris L.) leaf tissues reveal a spatial segregation of gE1- and gE2-labeling patterns. The gE1 antibodies bind only to the cellulose-rich region of the cell wall (J.P. Staehelin and L.A. Stafstrom [1988] Planta 174: 321-332), whereas gE2 labeling is restricted to the expanded middle lamella at three cell junctions. Periodate oxidation of nonosmicated, thin-sectioned tissue abolishes gE1 labeling but leads to labeling of the entire cell wall by gE2, presumably as a result of unmasking cryptic epitopes on extensin-1 in the cellulose layer. Purified extensin-2 protein is more efficient than extensin-1 protein at agglutinating avirulent Pseudomonas strains lacking extracellular polysaccharide. Our results indicate that extensin-2 does not form a heterologous HRGP network with extensin-1 and that, in contrast to extensin-1, which appears to serve a structural role, extensin-2 could participate in passive defense responses against phytopathogenic bacteria.
Structure type: oligomer
Location inside paper: Fig. 11
Contained glycoepitopes: IEDB_136907
NCBI Taxonomy refs (TaxIDs): 4039Reference(s) to other database(s): CCSD:
18161, CBank-STR:7211
Show glycosyltransferases
There is only one chemically distinct structure:
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