title: Sugarcane glycoproteins may act as signals for the production of xanthan in the plant-associated bacterium Xanthomonas albilineans.
abstract: Visual symptoms of leaf scald necrosis in sugarcane (Saccharum officinarum) leaves develop in parallel to the accumulation of a fibrous material invading exocellular spaces and both xylem and phloem. These fibers are produced and secreted by the plant-associated bacterium Xanthomonas albilineans. Electron microscopy and specific staining methods for polysaccharides reveal the polysaccharidic nature of this material. These polysaccharides are not present in healthy leaves or in those from diseased plants without visual symptoms of leaf scald. Bacteria in several leaf tissues have been detected by immunogold labelling. The bacterial polysaccharide is not produced in axenic culture but it is actively synthesized when the microbes invade the host plant. This finding may be due to the production of plant glycoproteins after bacteria infection, which inhibit microbial proteases. In summary, our data are consistent with the existence of a positive feedback loop in which plant-produced glycoproteins act as a cell-to-bacteria signal that promotes xanthan production, by protecting some enzymes of xanthan biosynthesis against from bacterial proteolytic degradation.
authors.affiliation: Intercellular Communication in Plant Symbiosis Team, Faculty of Biology, Madrid, Spain.
authors.forename: María-Estrella
authors.initials: ME
authors.lastname: Legaz
authors.forename: María
authors.initials: M
authors.lastname: Blanch
authors.forename: Dolores
authors.initials: D
authors.lastname: Piñón
authors.forename: Rocío
authors.initials: R
authors.lastname: Santiago
authors.forename: Blanca
authors.initials: B
authors.lastname: Fontaniella
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Blanco
authors.forename: María-Teresa
authors.initials: MT
authors.lastname: Solas
authors.forename: Carlos
authors.initials: C
authors.lastname: Vicente
mesh_terms: D006023:Glycoproteins / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology / Q000648:ultrastructure; D010940:Plant Proteins / Q000378:metabolism*; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis*; D031786:Saccharum / Q000378:metabolism / Q000382:microbiology*; D014974:Xanthomonas / Q000378:metabolism* / Q000472:pathogenicity
chemical_list: D006023:Glycoproteins; D010940:Plant Proteins; D011135:Polysaccharides, Bacterial; C002563:xanthan gum