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Medientyp:
E-Artikel
Titel:
The iron‐stress activated RNA 1 (IsaR1) coordinates osmotic acclimation and iron starvation responses in the cyanobacterium Synechocystis sp. PCC 6803
Beteiligte:
Rübsam, Henriette;
Kirsch, Friedrich;
Reimann, Viktoria;
Erban, Alexander;
Kopka, Joachim;
Hagemann, Martin;
Hess, Wolfgang R.;
Klähn, Stephan
Beschreibung:
<jats:title>Summary</jats:title><jats:p>In nature, microorganisms are exposed to multiple stress factors in parallel. Here, we investigated the response of the model cyanobacterium <jats:italic>Synechocystis</jats:italic> sp. PCC 6803 to simultaneous iron limitation and osmotic stresses. Iron is a major limiting factor for bacterial and phytoplankton growth in most environments. Thus, bacterial iron homeostasis is tightly regulated. In <jats:italic>Synechocystis</jats:italic>, it is mediated mainly by the transcriptional regulator FurA and the <jats:styled-content>i</jats:styled-content>ron‐<jats:styled-content>s</jats:styled-content>tress <jats:styled-content>a</jats:styled-content>ctivated <jats:styled-content>R</jats:styled-content>NA <jats:styled-content>1</jats:styled-content> (IsaR1). IsaR1 is an important riboregulator that affects the acclimation of the photosynthetic apparatus to iron starvation in multiple ways. Upon increases in salinity, <jats:italic>Synechocystis</jats:italic> responds by accumulating the compatible solute glucosylglycerol (GG). We show that IsaR1 overexpression causes a reduction in the <jats:italic>de novo</jats:italic> GG synthesis rate upon salt shock. We verified the direct interaction between IsaR1 and the 5′UTR of the <jats:italic>ggpS</jats:italic> mRNA, which in turn drastically reduced the <jats:italic>de novo</jats:italic> synthesis of the key enzyme for GG synthesis, <jats:styled-content>g</jats:styled-content>lucosyl<jats:styled-content>g</jats:styled-content>lycerol <jats:styled-content>p</jats:styled-content>hosphate <jats:styled-content>s</jats:styled-content>ynthase (GgpS). Thus, IsaR1 specifically interferes with the salt acclimation process in <jats:italic>Synechocystis</jats:italic>, in addition to its primary regulatory function. Moreover, the salt‐stimulated GgpS production became reduced under parallel iron limitation in WT – an effect which is, however, attenuated in an <jats:italic>isaR1</jats:italic> deletion strain. Hence, IsaR1 is involved in the integration of the responses to different environmental perturbations and slows the osmotic adaptation process in cells suffering from parallel iron starvation.</jats:p>