Regulation of Photosynthesis Genes in
            <i>Rubrivivax gelatinosus</i>
            : Transcription Factor PpsR Is Involved in both Negative and Positive Control

Steunou, Anne-Soisig; Astier, Chantal; Ouchane, Soufian

doi:10.1128/jb.186.10.3133-3142.2004

Cited by 28 publications

(29 citation statements)

References 30 publications

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“…Two potential promoters, P1 and P2, exhibiting an E. coli-like 70 sequence motif were identified at Ϫ126 and Ϫ180 bp from the pucB start codon. Two copies of a conserved repressor PpsR recognition palindrome (TGT-N 12 -ACG/A) at Ϫ137 and Ϫ110 bp from the pucB initiation codon were also identified, involving PpsR in pucBA expression (34). Sequences that might form hairpin structures were found ( Fig.…”

Section: Characterizationmentioning

confidence: 99%

Involvement of the C-Terminal Extension of the α Polypeptide and of the PucC Protein in LH2 Complex Biosynthesis inRubrivivax gelatinosus

et al. 2004

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The facultative phototrophic nonsulfur bacterium Rubrivivax gelatinosus exhibits several differences from other species of purple bacteria in the organization of its photosynthetic genes. In particular, the puc operon contains only the pucB and pucA genes encoding the ␤ and ␣ polypeptides of the light-harvesting 2 (LH2) complex. Downstream of the pucBA operon is the pucC gene in the opposite transcriptional orientation. The transcription of pucBA and pucC has been studied. No pucC transcript was detected either by Northern blotting or by reverse transcription-PCR analysis. The initiation site of pucBA transcription was determined by primer extension, and Northern blot analysis revealed the presence of two transcripts of 0.8 and 0.65 kb. The half-lives of both transcripts are longer in cells grown semiaerobically than in photosynthetically grown cells, and the small transcript is the less stable. It was reported that the ␣ polypeptide, encoded by the pucA gene, presents a C-terminal extension which is not essential for LH2 function in vitro. The biological role of this alanine-and proline-rich C-terminal extension in vivo has been investigated. Two mutants with C-terminal deletions of 13 and 18 residues have been constructed. Both present the two pucBA transcripts, while their phenotypes are, respectively, LH2؉ and LH2 ؊ , suggesting that a minimal length of the C-terminal extension is required for LH2 biogenesis. Another important factor involved in the LH2 biogenesis is the PucC protein. To gain insight into the function of this protein in R. gelatinosus, we constructed and characterized a PucC mutant. The mutant is devoid of LH2 complex under semiaerobiosis but still produces a small amount of these antennae under photosynthetic growth conditions. This conditional phenotype suggests the involvement of another factor in LH2 biogenesis.Rubrivivax gelatinosus is a facultative phototrophic nonsulfur bacterium belonging to the ␤ subclass of Proteobacteria. Most of the photosynthetic genes are grouped in the photosynthetic cluster on the genome. Differences between the gene organization of the R. gelatinosus photosynthetic cluster and those of the ␣ subclass have been reported (13,25,32).Absorption of light and its conversion into chemical energy is performed, in general, by three highly organized transmembrane pigment-protein complexes: two light-harvesting (LH) complexes (LH1 and LH2) and the reaction center (RC) they surround. The light energy is initially trapped by the peripheral antenna LH2 complexes and transferred to LH1 complexes that are closely associated with the RC. The subsequent photon-induced charge separation in the RC initiates a cyclic electron transport and the formation of an electrochemical proton gradient across the membrane that requires the cytochrome bc 1 complex. The antenna complexes show distinct absorption spectra in the infrared, with maxima near 875 nm for LH1 and 800 and 850 nm for LH2 (12).Antenna complexes have been isolated from various species of purple bacteria. The three-dimens...

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Section: Characterizationmentioning

confidence: 99%

Involvement of the C-Terminal Extension of the α Polypeptide and of the PucC Protein in LH2 Complex Biosynthesis inRubrivivax gelatinosus

et al. 2004

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“…This circuit includes the two-component signal transduction system PrrBA (RegBA), the PpsR and FnrL transcriptional factors. So far, in R. gelatinosus only PpsR and FnrL were identified (16,20).…”

Section: ϫ -Bdmentioning

confidence: 99%

Adaptation to Oxygen

Hassani

Steunou

Liotenberg

et al. 2010

Journal of Biological Chemistry

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The appearance of oxygen in the Earth's atmosphere via oxygenic photosynthesis required strict anaerobes and obligate phototrophs to cope with the presence of this toxic molecule. Here we show that in the anoxygenic phototroph Rubrivivax gelatinosus, the terminal oxidases (cbb 3 , bd, and caa 3 ) expand the range of ambient oxygen tensions under which the organism can initiate photosynthesis. Unlike the wild type, the cbb 3 ؊ /bd ؊ double mutant can start photosynthesis only in deoxygenated medium or when oxygen is removed, either by sparging cultures with nitrogen or by co-inoculation with strict aerobes bacteria. In oxygenated environments, this mutant survives nonphotosynthetically until the O 2 tension is reduced. The cbb 3 and bd oxidases are therefore required not only for respiration but also for reduction of the environmental O 2 pressure prior to anaerobic photosynthesis. Suppressor mutations that restore respiration simultaneously restore photosynthesis in nondeoxygenated medium. Furthermore, induction of photosystem in the cbb 3 ؊ mutant led to a highly unstable strain. These results demonstrate that photosynthetic metabolism in environments exposed to oxygen is critically dependent on the O 2 -detoxifying action of terminal oxidases.

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“…The roles of PpsR and PpaA have not been clearly defined (9,12,19,34), and biochemical studies of R. denitrificans and other AAPs are needed to clarify their function. Furthermore, AAP genome sequences may reveal patterns in regulatory proteins that could lead to a better understanding of aerobic phototrophy.…”

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confidence: 99%

“…Although R. denitrificans encodes a homolog of PpsR (RD1_0143), aerobic gene repression would be counterproductive to the observed aerobic photosynthetic expression. Interestingly, PpsR in R. gelatinosus and PpsR1 in Bradyrhizobium strain ORS278 have been proposed to activate photosynthesis gene transcription under aerobiosis (19,34).…”

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The Complete Genome Sequence of Roseobacter denitrificans Reveals a Mixotrophic Rather than Photosynthetic Metabolism

et al. 2007

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Purple aerobic anoxygenic phototrophs (AAPs) are the only organisms known to capture light energy to enhance growth only in the presence of oxygen but do not produce oxygen. The highly adaptive AAPs compose more than 10% of the microbial community in some euphotic upper ocean waters and are potentially major contributors to the fixation of the greenhouse gas CO 2 . We present the complete genomic sequence and feature analysis of the AAP Roseobacter denitrificans, which reveal clues to its physiology. The genome lacks genes that code for known photosynthetic carbon fixation pathways, and most notably missing are genes for the Calvin cycle enzymes ribulose bisphosphate carboxylase (RuBisCO) and phosphoribulokinase. Phylogenetic evidence implies that this absence could be due to a gene loss from a RuBisCO-containing ␣-proteobacterial ancestor. We describe the potential importance of mixotrophic rather than autotrophic CO 2 fixation pathways in these organisms and suggest that these pathways function to fix CO 2 for the formation of cellular components but do not permit autotrophic growth. While some genes that code for the redox-dependent regulation of photosynthetic machinery are present, many light sensors and transcriptional regulatory motifs found in purple photosynthetic bacteria are absent.Among the five major phyla containing phototrophic prokaryotes, the purple proteobacteria are the most metabolically diverse. The anaerobic purple photosynthetic bacteria grow photoautotrophically only at low oxygen levels, while at higher oxygen levels, the photosynthetic apparatus is down-regulated, resulting in chemotrophic growth using organic carbon (3). In contrast, some related marine ␣-proteobacteria produce bacteriochlorophyll (BChl) a only in the presence of oxygen in the dark (39). These aerobic anoxygenic phototrophs (AAPs) (also known as AAnP or APB for aerobic phototrophic bacteria) have long been overlooked in oceanic studies, but recent data indicate that their contribution to the global carbon cycle could be significant (22).Typically, AAPs grow photoheterotrophically by respiration of organic substrates (39), resulting in the release of CO 2 , counter to the traditional "CO 2 sink" of the upper ocean. However, light-stimulated CO 2 uptake has been seen in some AAP species (22, 39), and several members of the Roseobacter clade were shown to oxidize CO to CO 2 (6).The marine AAP species Roseobacter denitrificans grows not only photoheterotrophically in the presence of oxygen and light but also anaerobically in the dark using nitrate or trimethylamine N-oxide as an electron acceptor (39). This adaptability has made R. denitrificans the most studied AAP and a model organism for this group.Our study of the R. denitrificans genome reveals a variety of metabolic options available to make this species successful in a competitive oligotrophic marine environment. We also investigated the complement of transcriptional regulators in R. denitrificans that are thought to be responsible for aerobic regulation of photosyn...

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Regulation of Photosynthesis Genes in Rubrivivax gelatinosus : Transcription Factor PpsR Is Involved in both Negative and Positive Control

Cited by 28 publications

References 30 publications

Involvement of the C-Terminal Extension of the α Polypeptide and of the PucC Protein in LH2 Complex Biosynthesis inRubrivivax gelatinosus

Involvement of the C-Terminal Extension of the α Polypeptide and of the PucC Protein in LH2 Complex Biosynthesis inRubrivivax gelatinosus

Adaptation to Oxygen

The Complete Genome Sequence of Roseobacter denitrificans Reveals a Mixotrophic Rather than Photosynthetic Metabolism

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