Role of calcium in acclimation of the cyanobacterium Synechococcus elongatus PCC 7942 to nitrogen starvation.
A Ca2+ signal is required for the process of heterocyst differentiation in the filamentous diazotrophic cyanobacterium Anabaena sp. PCC 7120. This paper presents evidence that a transient increase in intracellular free Ca2+ is also involved in acclimation to nitrogen starvation in the unicellular non-diazotrophic cyanobacterium Synechococcus elongatus PCC 7942. The Ca2+ transient was triggered in response to nitrogen step-down or the addition of 2-oxoglutarate (2-OG), or its analogues 2,2-difluoropentanedioic acid (DFPA) and 2-methylenepentanedioic acid (2-MPA), to cells growing with combined nitrogen, suggesting that an increase in intracellular 2-OG levels precedes the Ca2+ transient. The signalling protein P(II) and the transcriptional regulator NtcA appear to be needed to trigger the signal. Suppression of the Ca2+ transient by the intracellular Ca2+ chelator N,N'-[1,2-ethanediylbis(oxy-2,1-phenylene)]bis[N-[2-[(acetyloxy)methoxy]-2-oxoethyl]]-,bis[(acetyloxy)methyl] ester (BAPTA-AM) inhibited expression of the glnB and glnN genes, which are involved in acclimation to nitrogen starvation and transcriptionally activated by NtcA. BAPTA-AM treatment partially inhibited expression of the nblA gene, which is involved in phycobiliprotein degradation following nutrient starvation and is regulated by NtcA and NblR; in close agreement, BAPTA-AM treatment partially inhibited bleaching following nitrogen starvation. Taken together, the results presented here strongly suggest an involvement of a defined Ca2+ transient in acclimation of S. elongatus to nitrogen starvation through NtcA-dependent regulation.
Leganés
Francisco
F
Departamento de Biología, Universidad Autónoma de Madrid, Madrid 28049, Spain.
Forchhammer
Karl
K
Lehrstuhl für Mikrobiologie-Organismische Interaktionen, Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany.
Fernández-Piñas
Francisca
F
Departamento de Biología, Universidad Autónoma de Madrid, Madrid 28049, Spain.
D000222:Adaptation, Physiological; D000331:Aequorin / Q000378:metabolism; D001059:Apoproteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D003470:Culture Media; D015964:Gene Expression Regulation, Bacterial; D018869:Heat-Shock Response; D007656:Ketoglutaric Acids / Q000378:metabolism; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism*; D051922:PII Nitrogen Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism; D046940:Synechococcus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism
D001059:Apoproteins; D001426:Bacterial Proteins; D002135:Calcium-Binding Proteins; D003470:Culture Media; D007656:Ketoglutaric Acids; D051922:PII Nitrogen Regulatory Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; C060014:apoaequorin; D000331:Aequorin; D013455:Sulfur; D009584:Nitrogen; D002118:Calcium