title: A Putative O-Linked β-N-Acetylglucosamine Transferase Is Essential for Hormogonium Development and Motility in the Filamentous Cyanobacterium Nostoc punctiforme.
abstract: 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 achieved only after the transient differentiation of hormogonia, which are specialized filaments that enter a nongrowth state dedicated to motility. Despite the fundamental importance of hormogonia to the life cycles 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 cyanobacteriumNostoc punctiforme, a forward genetic screen was employed. The first gene identified using this screen, designatedogtA, encodes a putative O-linked β-N-acetylglucosamine transferase (OGT). The deletion ofogtAabolished motility, while ectopic expression ofogtAinduced hormogonium development even under hormogonium-repressing conditions. Transcription ofogtAis rapidly upregulated (1 h) following hormogonium induction, and an OgtA-GFPuv fusion protein localized to the cytoplasm. In developing hormogonia, accumulation of PilA but not HmpD is dependent onogtAReverse transcription-quantitative PCR (RT-qPCR) analysis indicated equivalent levels ofpilAtranscript in the wild-type and ΔogtAmutant strains, while a reporter construct consisting of the intergenic region in the 5' direction ofpilAfused togfpproduced lower levels of fluorescence in the ΔogtAmutant strain than in the wild type. The production of hormogonium polysaccharide in the ΔogtAmutant strain is reduced compared to that in the wild type but comparable to that in apilAdeletion strain. Collectively, these results imply thatO-GlcNAc protein modification regulates the accumulation of PilA via a posttranscriptional mechanism in developing hormogonia.IMPORTANCEFilamentous cyanobacteria are among the most developmentally complex prokaryotes. Species such asNostoc punctiformedevelop an array of cell types, including nitrogen-fixing heterocysts, spore-like akinetes, and motile hormogonia, that function in dispersal as well as the establishment of nitrogen-fixing symbioses with plants and fungi. These symbioses are major contributors to global nitrogen fixation. Despite the fundamental importance of hormogonia to the life cycle of filamentous cyanobacteria and the establishment of symbioses, the molecular regulation of hormogonium development is largely undefined. We employed a genetic screen to identify genes essential for hormogonium development and motility inNostoc punctiformeThe first gene identified using this screen encodes a eukaryotic-like O-linked β-N-acetylglucosamine transferase that is required for accumulation of PilA in hormogonia.
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA.
authors.forename: Behzad
authors.initials: B
authors.lastname: Khayatan
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA.
authors.forename: Divleen K
authors.initials: DK
authors.lastname: Bains
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA.
authors.forename: Monica H
authors.initials: MH
authors.lastname: Cheng
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA.
authors.forename: Ye Won
authors.initials: YW
authors.lastname: Cho
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Huynh
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA.
authors.forename: Rachelle
authors.initials: R
authors.lastname: Kim
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA.
authors.forename: Osagie H
authors.initials: OH
authors.lastname: Omoruyi
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA.
authors.forename: Adriana P
authors.initials: AP
authors.lastname: Pantoja
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA.
authors.forename: Jun Sang
authors.initials: JS
authors.lastname: Park
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA.
authors.forename: Julia K
authors.initials: JK
authors.lastname: Peng
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA.
authors.forename: Samantha D
authors.initials: SD
authors.lastname: Splitt
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA.
authors.forename: Mason Y
authors.initials: MY
authors.lastname: Tian
authors.affiliation: Department of Biology, University of the Pacific, Stockton, California, USA drisser@pacific.edu.
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Risser
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000502:physiology; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D009068:Movement; D009154:Mutation; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics / Q000378:metabolism*; D046937:Nostoc / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D017351:N-Acetylglucosaminyltransferases
keywords: Nostoc punctiforme; O-linked β-N-acetylglucosamine transferase; gliding motility; hormogonia; type IV pili