Title

Identification of Genes Involved in Hormogonium Polysaccharide Synthesis in Nostoc punctiforme

Poster Number

22A

Lead Author Major

Health & Exercise Science

Lead Author Status

Senior

Second Author Major

Biological Sciences

Second Author Status

Junior

Third Author Major

Pre-Dentistry

Third Author Status

Junior

Format

Poster Presentation

Faculty Mentor Name

Douglas Risser

Faculty Mentor Email

drisser@pacific.edu

Faculty Mentor Department

Biological Sciences

Abstract/Artist Statement

The goal of this project is to identify the genes essential for hormogonium development and motility in the filamentous cyanobacterium, Nostoc punctiforme. N. punctiforme differentiates hormogonia, which are motile filaments that can establish nitrogen-fixing symbioses with plants and fungi, and perform phototaxis. Hormogonium motility is driven by a modified type IV pilus-like system that secretes a polysaccharide essential for motility. Using a transposon mutagenesis screen, a large number of genes were identified that appear to be involved in HPS (hormogonia polysaccharide) synthesis. These genes involved in HPS synthesis also appear to co-occur among many species of cyanobacteria. An in-depth analysis of NpR0640, NpR0638, and NpR1506 was performed to assess their role in HPS synthesis. In-frame deletion strains of NpR0640, NpR0638, and NpR1506 were created and their phenotypes were observed. The gene regulatory network that controls hormogonium development has two distinct pathways, one that promotes the transcription of pilA and one the other promoting the transcription of the hmp locus, which leads to HPS synthesis. Samples were induced for hormogonia and 24-hours later were imaged with light microscopy, stained for polysaccharide and pilA, and imaged with fluorescent microscopy to assess polysaccharide synthesis. All three mutant strains were non-motile, produced hormogonia, and secreted pilA, indicating a functional Type IV pilus-like system. However, none of them produced HPS. These results indicate that the three genes are essential for HPS synthesis, and supports the hypothesis that HPS is essential for motility in Nostoc punctiforme.

Location

DeRosa University Center, Ballroom

Start Date

28-4-2018 10:00 AM

End Date

28-4-2018 12:00 PM

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Apr 28th, 10:00 AM Apr 28th, 12:00 PM

Identification of Genes Involved in Hormogonium Polysaccharide Synthesis in Nostoc punctiforme

DeRosa University Center, Ballroom

The goal of this project is to identify the genes essential for hormogonium development and motility in the filamentous cyanobacterium, Nostoc punctiforme. N. punctiforme differentiates hormogonia, which are motile filaments that can establish nitrogen-fixing symbioses with plants and fungi, and perform phototaxis. Hormogonium motility is driven by a modified type IV pilus-like system that secretes a polysaccharide essential for motility. Using a transposon mutagenesis screen, a large number of genes were identified that appear to be involved in HPS (hormogonia polysaccharide) synthesis. These genes involved in HPS synthesis also appear to co-occur among many species of cyanobacteria. An in-depth analysis of NpR0640, NpR0638, and NpR1506 was performed to assess their role in HPS synthesis. In-frame deletion strains of NpR0640, NpR0638, and NpR1506 were created and their phenotypes were observed. The gene regulatory network that controls hormogonium development has two distinct pathways, one that promotes the transcription of pilA and one the other promoting the transcription of the hmp locus, which leads to HPS synthesis. Samples were induced for hormogonia and 24-hours later were imaged with light microscopy, stained for polysaccharide and pilA, and imaged with fluorescent microscopy to assess polysaccharide synthesis. All three mutant strains were non-motile, produced hormogonia, and secreted pilA, indicating a functional Type IV pilus-like system. However, none of them produced HPS. These results indicate that the three genes are essential for HPS synthesis, and supports the hypothesis that HPS is essential for motility in Nostoc punctiforme.