title: Evidence for the involvement of surface carbohydrates in the recognition of Haematococcus pluvialis by the parasitic blastoclad Paraphysoderma sedebokerensis.
abstract: The unicellular green alga Haematococcus pluvialis (Chlorophyta, Volvocales) is currently the best commercial source of the natural red ketocarotenoid astaxanthin. Paraphysoderma sedebokerensis (Blastocladiomycota), a parasitic blastoclad that is specific for this microalga, was recently isolated and identified in our laboratory. In this study, we investigated the recognition process between the parasite and H. pluvialis. Obligatory requirements for recognition were identified as an ion concentration in the medium of 20 mM, the presence of calcium ions, and neutral to basic conditions; these requirements imply that a protein is involved in the process. In a search for potential lectin-sugar interactions as a major event in the recognition process, we screened for exposed glycosidic moieties on the cell wall of the alga and on the parasite zoospore surface. Competition experiments with the appropriate lectins and monosugars identified Ricinus communis agglutinin (RCA(120)) as the lectin that recognizes Gal-N-acetyl-d-glucosamine, an oligosaccharide located on the host. We propose that an RCA(120)-like lectin-sugar interaction mediates the highly specific interaction between the blastocladian parasite and its algal host.
authors.affiliation: Microalgal Biotechnology Laboratory, The Albert Katz Department of Dryland Biotechnologies, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boker Campus 84990, Israel.
authors.forename: Jenia
authors.initials: J
authors.lastname: Gutman
authors.forename: Aliza
authors.initials: A
authors.lastname: Zarka
authors.forename: Sammy
authors.initials: S
authors.lastname: Boussiba
mesh_terms: D055133:Blastocladiomycota / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D000460:Chlorophyta / Q000378:metabolism* / Q000382:microbiology*; D054884:Host-Pathogen Interactions; D009844:Oligosaccharides / Q000378:metabolism; D037121:Plant Lectins / Q000378:metabolism
chemical_list: D009844:Oligosaccharides; D037121:Plant Lectins; C017707:Ricinus communis agglutinin-1