title: 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.
authors: Department of Electrical Engineering and Biological Science, Waseda University, Tokyo, Japan.
authors: Hiroko
authors: H
authors: Kushige
authors: Hideyuki
authors: H
authors: Kugenuma
authors: Masaki
authors: M
authors: Matsuoka
authors: Shigeki
authors: S
authors: Ehira
authors: Masayuki
authors: M
authors: Ohmori
authors: Hideo
authors: H
authors: Iwasaki
mesh_terms: D017033:Anabaena / Q000235:genetics* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D057906:Circadian Clocks; D002940:Circadian Rhythm; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D009586:Nitrogen Fixation / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114269:KaiA protein, cyanobacteria; C114270:KaiB protein, cyanobacteria; C114271:KaiC protein, cyanobacteria