title: The non-metabolizable sucrose analog sucralose is a potent inhibitor of hormogonium differentiation in the filamentous cyanobacterium Nostoc punctiforme.
abstract: Nostoc punctiforme is a filamentous cyanobacterium which forms nitrogen-fixing symbioses with several different plants and fungi. Establishment of these symbioses requires the formation of motile hormogonium filaments. Once infected, the plant partner is thought to supply a hormogonium-repressing factor (HRF) to maintain the cyanobacteria in a vegetative, nitrogen-fixing state. Evidence implies that sucrose may serve as a HRF. Here, we tested the effects of sucralose, a non-metabolizable sucrose analog, on hormogonium differentiation. Sucralose inhibited hormogonium differentiation at a concentration approximately one-tenth that of sucrose. This result implies that: (1) sucrose, not a sucrose catabolite, is perceived by the cell and (2) inhibition is not due to a more general osmolarity-dependent effect. Additionally, both sucrose and sucralose induced the accrual of a polysaccharide sheath which bound specifically to the lectin ConA, indicating the presence of α-D-mannose and/or α-D-glucose. A ConA-specific polysaccharide was also found to be expressed in N. punctiforme colonies from tissue sections of the symbiotically grown hornwort Anthoceros punctatus. These findings imply that plant-derived sucrose or sucrose analogs may have multiple effects on N. punctiforme, including both repression of hormogonia and the induction of a polysaccharide sheath that may be essential to establish and maintain the symbiotic state.
authors.affiliation: Department of Biology, University of the Pacific, Stockton, CA, 95211, USA.
authors.forename: Samantha D
authors.initials: SD
authors.lastname: Splitt
authors.affiliation: Department of Biology, University of the Pacific, Stockton, CA, 95211, USA. drisser@pacific.edu.
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Risser
mesh_terms: D019684:Magnoliopsida / Q000382:microbiology; D046937:Nostoc / Q000187:drug effects* / Q000254:growth & development; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D013395:Sucrose / Q000031:analogs & derivatives* / Q000494:pharmacology; D013559:Symbiosis
chemical_list: D011135:Polysaccharides, Bacterial; D013395:Sucrose; C026285:trichlorosucrose
keywords: Anthoceros punctatus; Hormogonia; Nostoc punctiforme; Sucralose; Sucrose; Symbiosis