Gene expression under low-oxygen conditions in the cyanobacterium Synechocystis sp. PCC 6803 demonstrates Hik31-dependent and -independent responses

Summerfield, Tina C.; Nagarajan, Sowmya; Sherman, Louis A.

doi:10.1099/mic.0.041053-0

Cited by 32 publications

(45 citation statements)

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“…Liquid cultures were grown in BG-11 medium buffered with 25 to 40 mM HEPES-NaOH (pH 7.5) in 250-ml Erlenmeyer flasks. Low-O 2 growth experiments were performed with a 6-liter bioreactor (BioFlo 3000), and high-CO 2 experiments were performed with 750-ml Cytolifts (Kontes, Inc.) (36). Spectinomycin and kanamycin (25 g/ml) and chloramphenicol (10 g/ml) were added to the medium for specific mutant strains.…”

Section: Methodsmentioning

confidence: 99%

“…A putative double hik31 mutant has been implicated in the response to glucose (11). Also, a chromosomal ⌬hik31 mutant has implicated Hik31 as a transcriptional repressor under low-O 2 conditions affecting photosynthetic and ribosomal genes (36). Additionally, both sets of operons are close to genes predicted to be Zn 2ϩ /Co 2ϩ cation transporters, suggesting that these 2CSs may control the transduction of cation signals (12).…”

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confidence: 99%

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Functions of the Duplicated hik31 Operons in Central Metabolism and Responses to Light, Dark, and Carbon Sources in Synechocystis sp. Strain PCC 6803

et al. 2012

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There are two closely related hik31 operons involved in signal transduction on the chromosome and the pSYSX plasmid in the cyanobacterium Synechocystis sp. strain PCC 6803. We studied the growth, cell morphology, and gene expression in operon and hik mutants for both copies, under different growth conditions, to examine whether the duplicated copies have the same or different functions and gene targets and whether they are similarly regulated. Phenotype analysis suggested that both operons regulated common and separate targets in the light and the dark. The chromosomal operon was involved in the negative control of autotrophic events, whereas the plasmid operon was involved in the positive control of heterotrophic events. Both the plasmid and double operon mutant cells were larger and had division defects. The growth data also showed a regulatory role for the chromosomal hik gene under high-CO 2 conditions and the plasmid operon under low-O 2 conditions. Metal stress experiments indicated a role for the chromosomal hik gene and operon in mediating Zn and Cd tolerance, the plasmid operon in Co tolerance, and the chromosomal operon and plasmid hik gene in Ni tolerance. We conclude that both operons are differentially and temporally regulated. We suggest that the chromosomal operon is the primarily expressed copy and the plasmid operon acts as a backup to maintain appropriate gene dosages. Both operons share an integrated regulatory relationship and are induced in high light, in glucose, and in active cell growth. Additionally, the plasmid operon is induced in the dark with or without glucose. Bacteria use several devices to monitor their environment and coordinate appropriate adaptive changes to maximize survival. These include chemotaxis receptors, sigma factors, Ser/Thr protein kinases, and two-component systems (2CSs) (25). The prototypical 2CS consists of a histidine kinase (Hik) sensor that is a transmembrane protein and a response regulator (Rre) that usually binds to DNA and acts as a transcription factor, either activating or repressing the target genes or both. Each protein has two or more domains that perform the various functions and participate in phosphotransfer reactions and can be classified into different types (3,7,8,42). Higher-order 2CSs can have a more complex interaction with combinations of domains and cross talk between different partner 2CSs (7).Signal transduction systems in the freshwater model cyanobacterium Synechocystis sp. strain PCC 6803 (here Synechocystis) are important for sensing, responding to, and adapting to different environmental changes. The Synechocystis genome includes about 47 Hik proteins and 45 Rre proteins, and these make up Ͼ2.5% of the genome. Although most of these are located on the chromosome, 3 each of the Hik proteins and Rre proteins are found on plasmids pSYSX and pSYSM. Unlike in other bacteria, the positions of these genes are scattered throughout the genome, and only 14 sets or 32 open reading frames are in close proximity to each other. The domains of the...

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Section: Methodsmentioning

confidence: 99%

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Functions of the Duplicated hik31 Operons in Central Metabolism and Responses to Light, Dark, and Carbon Sources in Synechocystis sp. Strain PCC 6803

et al. 2012

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“…9 Later it was also shown to be induced under other conditions that alter the electron transport rate around PSI, such as sulfur and nitrogen starvation or low oxygen. [10][11][12] We have shown that copper is strictly required for these inductions, suggesting that these are indirect effects of reduction of photosynthetic electron transport. Plastocyanin, which is the main copper containing protein in Synechocystis, it is also the major difference between photosynthetic electron transport chains in copper replete and copper free medium.…”

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Redox control of copper homeostasis in cyanobacteria

López‐Maury

Giner‐Lamia²,

Florencio

2012

Plant Signaling & Behavior

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“…The expression of the flv4-2 operon is, in fact, induced only at LC and/or HL conditions, when cyanobacterial cells show a chronically sensitive phenotype to photoinhibition. In addition, the operon is induced in the absence of oxygen (Summerfield et al, 2011), a condition in which the function of terminal Figure 10. The 77K fluorescence emission spectra of wild-type, DpsbA2, flv4-2/OE, and Dflv4 strains excited at 580 nm.…”

Section: The Flv2/flv4 Heterodimer Functions As An Important Electronmentioning

confidence: 99%

Flavodiiron Protein Flv2/Flv4-Related Photoprotective Mechanism Dissipates Excitation Pressure of PSII in Cooperation with Phycobilisomes in Cyanobacteria

et al. 2013

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(A.R., I.V.) Oxygenic photosynthesis evolved with cyanobacteria, the ancestors of plant chloroplasts. The highly oxidizing chemistry of water splitting required concomitant evolution of efficient photoprotection mechanisms to safeguard the photosynthetic machinery. The role of flavodiiron proteins (FDPs), originally called A-type flavoproteins or Flvs, in this context has only recently been appreciated. Cyanobacterial FDPs constitute a specific protein group that evolved to protect oxygenic photosynthesis. There are four FDPs in Synechocystis sp. PCC 6803 (Flv1 to Flv4). Two of them, Flv2 and Flv4, are encoded by an operon together with a Sll0218 protein.Their expression, tightly regulated by CO 2 levels, is also influenced by changes in light intensity. Here we describe the overexpression of the flv4-2 operon in Synechocystis sp. PCC 6803 and demonstrate that it results in improved photochemistry of PSII. The flv4-2/OE mutant is more resistant to photoinhibition of PSII and exhibits a more oxidized state of the plastoquinone pool and reduced production of singlet oxygen compared with control strains. Results of biophysical measurements indicate that the flv4-2 operon functions in an alternative electron transfer pathway from PSII, and thus alleviates PSII excitation pressure by channeling up to 30% of PSII-originated electrons. Furthermore, intact phycobilisomes are required for stable expression of the flv4-2 operon genes and for the Flv2/Flv4 heterodimer-mediated electron transfer mechanism. The latter operates in photoprotection in a complementary way with the orange carotenoid protein-related nonphotochemical quenching. Expression of the flv4-2 operon and exchange of the D1 forms in PSII centers upon light stress, on the contrary, are mutually exclusive photoprotection strategies among cyanobacteria.Photosynthetic light reactions are evolutionarily highly conserved among oxygenic photosynthetic organisms from cyanobacteria to higher plants. Because of dangerous chemistry of the water splitting reactions, oxygenic photosynthesis produces reactive oxygen species (ROS) and other radicals that potentially could destroy the photosynthetic machinery. To avoid permanent damage, all oxygenic photosynthetic organisms are equipped with an array of various photoprotective and regulatory mechanisms. Accumulating evidence on these regulatory mechanisms has revealed vast evolutionary differences between organisms performing oxygenic photosynthesis.Photosynthetic organisms have a capacity to adjust to different light intensities and to changes in the availability of electron sinks, which depends largely on metabolic cues. When light or metabolic conditions change, photosystems can dissipate excess energy as heat in nonphotochemical energy dissipation processes in the light-harvesting antenna systems (for review, see Horton et al., 1996;Müller et al., 2001). Cyanobacteria have phycobilisomes (PBs) as light-harvesting antenna, which also participate in state transitions (for review, see van Thor et al., 1998;Mullineaux ...

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Gene expression under low-oxygen conditions in the cyanobacterium Synechocystis sp. PCC 6803 demonstrates Hik31-dependent and -independent responses

Cited by 32 publications

References 59 publications

Functions of the Duplicated hik31 Operons in Central Metabolism and Responses to Light, Dark, and Carbon Sources in Synechocystis sp. Strain PCC 6803

Functions of the Duplicated hik31 Operons in Central Metabolism and Responses to Light, Dark, and Carbon Sources in Synechocystis sp. Strain PCC 6803

Redox control of copper homeostasis in cyanobacteria

Flavodiiron Protein Flv2/Flv4-Related Photoprotective Mechanism Dissipates Excitation Pressure of PSII in Cooperation with Phycobilisomes in Cyanobacteria

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