Date of Award


Document Type

Thesis - Pacific Access Restricted

Degree Name

Master of Science (M.S.)


American Academy of Asian Studies

First Advisor

Douglas Risser, Ph.D.

First Committee Member

Craig Vierra, Ph.D.

Second Committee Member

Geoffrey Lin-Cereghino, Ph.D.


Most species of filamentous cyanobacteria are capable of gliding motility, likely via a conserved type IV pilus-like system that may also secrete a motility-associated polysaccharide. In a subset of these organisms, motility is only achieved after the transient differentiation of hormogonia, specialized filaments that enter a non-growth state dedicated to motility. Despite the fundamental importance of hormogonia to the life cycle of many filamentous cyanobacteria, the molecular regulation of hormogonium development is largely undefined. To systematically identify genes essential for hormogonium development and motility in the model heterocyst-forming, filamentous cyanobacterium Nostoc punctiforme, a forward genetic screen was employed. The gene identified using this screen, designated ogtA, encodes a putative O-linked β-N-acetylglucosamine transferase (OGT). Deletion of ogtA abolished motility while ectopic expression of ogtA induced hormogonium development even under hormogonium repressing conditions. Transcription of ogtA is rapidly up-regulated (1 h) following hormogonium induction and an OgtA-GFPuv fusion protein localized to the cytoplasm. In developing hormogonia, accumulation of pilA transcript in the wild-type and ΔogtA strain, while a reporter construct consisting of the intergenic region 5' to pilA fused to gfp produced lower levels of fluorescence in the ΔogtA strain than the wild type. Production of hormogonium polysaccharide in the ΔogtA strain was reduced compared to the wild type, but comparable to that of a pilA-deletion strain. Collectively, these results imply that O-GlcNAc protein modification regulates the accumulation of PilA via a post-transcriptional mechanism in developing hormogonia.



To access this thesis/dissertation you must have a valid email address and log-in to Scholarly Commons.



Rights Statement

Rights Statement

In Copyright. URI:
This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).