Dataset Information

Genome-wide and heterocyst-specific circadian gene expression in the filamentous Cyanobacterium Anabaena sp. strain PCC 7120.

ABSTRACT: The filamentous, heterocystous cyanobacterium Anabaena sp. strain PCC 7120 is one of the simplest multicellular organisms that show both morphological pattern formation with cell differentiation (heterocyst formation) and circadian rhythms. Therefore, it potentially provides an excellent model in which to analyze the relationship between circadian functions and multicellularity. However, detailed cyanobacterial circadian regulation has been intensively analyzed only in the unicellular species Synechococcus elongatus. In contrast to the highest-amplitude cycle in Synechococcus, we found that none of the kai genes in Anabaena showed high-amplitude expression rhythms. Nevertheless, ~80 clock-controlled genes were identified. We constructed luciferase reporter strains to monitor the expression of some high-amplitude genes. The bioluminescence rhythms satisfied the three criteria for circadian oscillations and were nullified by genetic disruption of the kai gene cluster. In heterocysts, in which photosystem II is turned off, the metabolic and redox states are different from those in vegetative cells, although these conditions are thought to be important for circadian entrainment and timekeeping processes. Here, we demonstrate that circadian regulation is active in heterocysts, as shown by the finding that heterocyst-specific genes, such as all1427 and hesAB, are expressed in a robust circadian fashion exclusively without combined nitrogen.

SUBMITTER: Kushige H

PROVIDER: S-EPMC3592012 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature

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Genome-wide and heterocyst-specific circadian gene expression in the filamentous Cyanobacterium Anabaena sp. strain PCC 7120.

Kushige Hiroko H Kugenuma Hideyuki H Matsuoka Masaki M Ehira Shigeki S Ohmori Masayuki M Iwasaki Hideo H

Journal of bacteriology 20130111 6

The filamentous, heterocystous cyanobacterium Anabaena sp. strain PCC 7120 is one of the simplest multicellular organisms that show both morphological pattern formation with cell differentiation (heterocyst formation) and circadian rhythms. Therefore, it potentially provides an excellent model in which to analyze the relationship between circadian functions and multicellularity. However, detailed cyanobacterial circadian regulation has been intensively analyzed only in the unicellular species Sy ...[more]

PMID: 23316037

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Project description:When deprived of combined nitrogen, some filamentous cyanobacteria contain two cell types: vegetative cells that fix CO2 through oxygenic photosynthesis and heterocysts that are specialized in N2 fixation. In the diazotrophic filament, the vegetative cells provide the heterocysts with reduced carbon (mainly in the form of sucrose) and heterocysts provide the vegetative cells with combined nitrogen. Septal junctions traverse peptidoglycan through structures known as nanopores and appear to mediate intercellular molecular transfer that can be traced with fluorescent markers, including the sucrose analog esculin (a coumarin glucoside) that is incorporated into the cells. Uptake of esculin by the model heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 was inhibited by the α-glucosides sucrose and maltose. Analysis of Anabaena mutants identified components of three glucoside transporters that move esculin into the cells: GlsC (Alr4781) and GlsP (All0261) are an ATP-binding subunit and a permease subunit of two different ABC transporters, respectively, and HepP (All1711) is a major facilitator superfamily (MFS) protein that was shown previously to be involved in formation of the heterocyst envelope. Transfer of fluorescent markers (especially calcein) between vegetative cells of Anabaena was impaired by mutation of glucoside transporter genes. GlsP and HepP interact in bacterial two-hybrid assays with the septal junction-related protein SepJ, and GlsC was found to be necessary for the formation of a normal number of septal peptidoglycan nanopores and for normal subcellular localization of SepJ. Therefore, beyond their possible role in nutrient uptake in Anabaena, glucoside transporters influence the structure and function of septal junctions.IMPORTANCE Heterocyst-forming cyanobacteria have the ability to perform oxygenic photosynthesis and to assimilate atmospheric CO2 and N2 These organisms grow as filaments that fix these gases specifically in vegetative cells and heterocysts, respectively. For the filaments to grow, these types of cells exchange nutrients, including sucrose, which serves as a source of reducing power and of carbon skeletons for the heterocysts. Movement of sucrose between cells in the filament takes place through septal junctions and has been traced with a fluorescent sucrose analog, esculin, that can be taken up by the cells. Here, we identified α-glucoside transporters of Anabaena that mediate uptake of esculin and, notably, influence septal structure and the function of septal junctions.

Dataset Information

Genome-wide and heterocyst-specific circadian gene expression in the filamentous Cyanobacterium Anabaena sp. strain PCC 7120.

Publications

Genome-wide and heterocyst-specific circadian gene expression in the filamentous Cyanobacterium Anabaena sp. strain PCC 7120.

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