Title

Sucrose Analog Sucralose is Potent Inhibitor of Hormogonium Differentiation in Nostoc punctiforme

Poster Number

33

Lead Author Major

Biochemistry

Format

Poster Presentation

Faculty Mentor Name

Doug Risser

Faculty Mentor Department

Biological Sciences

Abstract/Artist Statement

Nostoc punctiforme is a filamentous cyanobacterium which forms nitrogen-fixing endosymbioses with several different plants and fungi. These symbioses play an important role in global nitrogen cycling and are responsible for half of all terrestrial nitrogen fixation. To establish endosymbioses, the cyanobacterium differentiates into hormogonia, motile filaments which form in response to a plant-derived hormogonium-inducing factor. Once the appropriate plant tissue is colonized a hormogonium-repressing factor (HRF) is thought to suppress hormogonium differentiation thereby maintaining the cyanobacteria as photosynthetic vegetative cells and nitrogen-fixing heterocysts. Evidence suggests that sucrose may serve as the plant-derived HRF. In order to further explore the role of sucrose as a signaling molecule regulating hormogonium development 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 implies that 1) sucrose, not a sucrose catabolic metabolite, is perceived by the cell and 2) inhibition is not due to a more general osmolarity-dependent effect, as only very low concentrations of sucralose were required to achieve the same effects as much higher concentrations of sucrose. In addition, both sucrose and sucralose were shown to induce the secretion of a polysaccharide sheath around the filaments, causing the filaments to clump more tightly with increasing concentrations. The polysaccharide bound specifically to the lectin ConA, indicating the presence of α-D-mannosyl and/or α-D-glucosyl groups. A ConA specific polysaccharide was also observed in N. punctiforme colonies from tissue sections of the symbiotically grown hornwort Anthoceros punctatus. These findings imply that plant derived sucrose has multiple effects on N. punctiforme including both repression of hormogonium and the induction of a polysaccharide sheath that may be essential to establish and maintain the symbiotic state.

Location

DeRosa University Center, Ballroom

Start Date

25-4-2015 2:00 PM

End Date

25-4-2015 4:00 PM

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Apr 25th, 2:00 PM Apr 25th, 4:00 PM

Sucrose Analog Sucralose is Potent Inhibitor of Hormogonium Differentiation in Nostoc punctiforme

DeRosa University Center, Ballroom

Nostoc punctiforme is a filamentous cyanobacterium which forms nitrogen-fixing endosymbioses with several different plants and fungi. These symbioses play an important role in global nitrogen cycling and are responsible for half of all terrestrial nitrogen fixation. To establish endosymbioses, the cyanobacterium differentiates into hormogonia, motile filaments which form in response to a plant-derived hormogonium-inducing factor. Once the appropriate plant tissue is colonized a hormogonium-repressing factor (HRF) is thought to suppress hormogonium differentiation thereby maintaining the cyanobacteria as photosynthetic vegetative cells and nitrogen-fixing heterocysts. Evidence suggests that sucrose may serve as the plant-derived HRF. In order to further explore the role of sucrose as a signaling molecule regulating hormogonium development 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 implies that 1) sucrose, not a sucrose catabolic metabolite, is perceived by the cell and 2) inhibition is not due to a more general osmolarity-dependent effect, as only very low concentrations of sucralose were required to achieve the same effects as much higher concentrations of sucrose. In addition, both sucrose and sucralose were shown to induce the secretion of a polysaccharide sheath around the filaments, causing the filaments to clump more tightly with increasing concentrations. The polysaccharide bound specifically to the lectin ConA, indicating the presence of α-D-mannosyl and/or α-D-glucosyl groups. A ConA specific polysaccharide was also observed in N. punctiforme colonies from tissue sections of the symbiotically grown hornwort Anthoceros punctatus. These findings imply that plant derived sucrose has multiple effects on N. punctiforme including both repression of hormogonium and the induction of a polysaccharide sheath that may be essential to establish and maintain the symbiotic state.