A eukaryotic BLUF domain mediates light-dependent gene expression in the purple bacterium
            <i>Rhodobacter sphaeroides</i>
            2.4.1

Han, Yuchen; Braatsch, Stephan; Osterloh, Lisa; Klug, Gabriele

doi:10.1073/pnas.0403547101

Cited by 64 publications

(70 citation statements)

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“…The ability of AppA to directly interact with PpsR and its antirepressor function were subsequently confirmed in vitro (29). AppA is unique in that it represents the first known protein that senses and integrates such different environmental stimuli as oxygen and light (3,20,29). The mechanism of light sensing by AppA through the novel type flavin adenine dinucleotide (FAD)-binding domain designated BLUF (14,18) is emerging (24,25).…”

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confidence: 99%

Transcriptome Analysis of the Rhodobacter sphaeroides PpsR Regulon: PpsR as a Master Regulator of Photosystem Development

2005

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PpsR from the anoxygenic phototrophic bacterium Rhodobacter sphaeroides has been known as an oxygenand light-dependent repressor of bacteriochlorophyll and carotenoid biosynthesis genes and puc operons involved in photosystem development. However, the putative PpsR-binding sites, TGTN 12 ACA, are also located upstream of numerous nonphotosystem genes, thus raising the possibility that the role of PpsR is broader. To characterize the PpsR regulon, transcriptome profiling was performed on the wild-type strain grown at high and low oxygen tensions, on the strain overproducing PpsR, and on the ppsR mutant. Transcriptome analysis showed that PpsR primarily regulates photosystem genes; the consensus PpsR binding sequence is TGTcN 10 gACA (lowercase letters indicate lesser conservation); the presence of two binding sites is required for repression in vivo. These findings explain why numerous single TGTN 12 ACA sequences are nonfunctional. In addition to photosystem genes, the hemC and hemE genes involved in the early steps of tetrapyrrole biosynthesis were identified as new direct targets of PpsR repression. Unexpectedly, PpsR was found to indirectly repress the puf and puhA operons encoding photosystem core proteins. The upstream regions of these operons contain no PpsR binding sites. Involvement in regulation of these operons suggests that PpsR functions as a master regulator of photosystem development. Upregulation of the puf and puhA operons that resulted from ppsR inactivation was sufficient to restore the ability to grow phototrophically to the prrA mutant. PrrA, the global redox-dependent activator, was previously considered indispensable for phototrophic growth. It is revealed that the PrrBA and AppA-PpsR systems, believed to work independently, in fact interact and coordinately regulate photosystem development.Rhodobacter sphaeroides is a facultatively phototrophic anoxygenic alphaproteobacterium. Under high oxygen tension, whether in the light or in the dark, this bacterium uses aerobic respiration for energy generation. When oxygen tension decreases, R. sphaeroides induces synthesis of photosynthetic apparatus, an alternate energy generation system functional under anoxic-light conditions (28,30,32,36). The photosynthetic apparatus is comprised of one type II photosystem (PS). Development of PS involves synthesis of photosynthetic pigments, bacteriochlorophyll (Bchl) and carotenoids (Crt), membrane proteins of the reaction center (RC), and two light-harvesting (LH) complexes as well as assembly factors. The RC and LH complexes are housed in the specialized intracytoplasmic membrane system. A decrease in oxygen tension triggers a significant increase in transcription of PS genes, which is required for PS development. Major regulatory components involved in oxygen control of PS development have been identified previously (1,44). However, precise roles of individual regulators and interactions between the regulatory pathways are not yet fully understood. This work is aimed at characterizing the role of one majo...

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Transcriptome Analysis of the Rhodobacter sphaeroides PpsR Regulon: PpsR as a Master Regulator of Photosystem Development

2005

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“…The idea of information modulation by attenuation has been proposed before [11]. The fact that cells in different metabolic states have different cellular components and different absorption spectra is well known and described in the literature [47][48][49]. We will not discuss this work further.…”

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“…Some pathways are already known [49,55,74]. We hope that this model inspires researchers to look at and for integrated pathways of photoreceptors.…”

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Light based cellular interactions: hypotheses and perspectives

Laager¹

2015

Front. Phys.

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This work investigates the theoretical possibility of interactions between cells via light. We first take a brief look at the previous research done in the past to have a better understanding of the field and the origins of the concept of cellular interactions. Then we identify the different elements essential for interactions between two parties. We then compare the required elements with the known and studied elements and characteristics which are well defined in biology, chemistry and physics. This way we are able to set up four postulates required for cell interactions: I. A signal is present and subject to secondary modulation by the emitter cells. II. There is a plastic information medium that reacts directly to the metabolic state of the emitter and therefore carries information about the emitter. III. An optical signal can be perceived by cells on a molecular level by a multitude of different receptors. IV. The information can in theory be processed by cells and metabolic changes in reaction to the signals can be observed. We demonstrate that all required elements have been observed. Most of them have important and well-known roles in cells. Therefore, we suggest that our hypothetical model is a good explanation for light based cellular interactions.

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“…The BLUF domain is also found in other bacteria (20) and in the PAC proteins of Euglena gracilis (27). It functions in modules, since it can signal to the C-terminal AppA output domain without covalent linkage (23). The C-terminal part of AppA is sufficient for normal redox regulation of photosynthesis genes (23).…”

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The AppA and PpsR Proteins from Rhodobacter sphaeroides Can Establish a Redox-Dependent Signal Chain but Fail To Transmit Blue-Light Signals in Other Bacteria

et al. 2007

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The AppA protein of Rhodobacter sphaeroides has the unique ability to sense and transmit redox and light signals. In response to decreasing oxygen tension, AppA antagonizes the transcriptional regulator PpsR, which represses the expression of photosynthesis genes, including the puc operon. This mechanism, which is based on direct protein-protein interaction, is prevented by blue-light absorption of the BLUF domain located in the N-terminal part of AppA. In order to test whether AppA and PpsR are sufficient to transmit redox and light signals, we expressed these proteins in three different bacterial species and monitored oxygen-and blue-lightdependent puc expression either directly or by using a luciferase-based reporter construct. The AppA/PpsR system could mediate redox-dependent gene expression in the alphaproteobacteria Rhodobacter capsulatus and Paracoccus denitrificans but not in the gammaproteobacterium Escherichia coli. Analysis of a prrA mutant strain of R. sphaeroides strongly suggests that light-dependent gene expression requires a balanced interplay of the AppA/PpsR system with the PrrA response regulator. Therefore, the AppA/PpsR system was unable to establish light signaling in other bacteria. Based on our data, we present a model for the interdependence of AppA/PpsR signaling and the PrrA transcriptional activator.

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A eukaryotic BLUF domain mediates light-dependent gene expression in the purple bacterium Rhodobacter sphaeroides 2.4.1

Cited by 64 publications

References 33 publications

Transcriptome Analysis of the Rhodobacter sphaeroides PpsR Regulon: PpsR as a Master Regulator of Photosystem Development

Transcriptome Analysis of the Rhodobacter sphaeroides PpsR Regulon: PpsR as a Master Regulator of Photosystem Development

Light based cellular interactions: hypotheses and perspectives

The AppA and PpsR Proteins from Rhodobacter sphaeroides Can Establish a Redox-Dependent Signal Chain but Fail To Transmit Blue-Light Signals in Other Bacteria

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