A Two-component Signal Transduction Pathway Regulates Manganese Homeostasis in Synechocystis 6803, a Photosynthetic Organism (original) (raw)
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Photosynthesis Research, 2015
High affinity transport of manganese ions (Mn 2?) in cyanobacteria is carried by an ABC-type transporter, encoded by the mntCAB operon, which is derepressed by the deficiency of Mn 2?. Transcription of this operon is negatively regulated by the two-component system consisting of a sensory histidine kinase ManS and DNA-binding response regulator ManR. In this study, we examined two Synechocystis mutants, defective in ManS and ManR. These mutants were unable to grow on high concentrations of manganese. Furthermore, they were sensitive to high light intensity and unable to recover after short-term photoinhibition. Under standard illumination and Mn 2? concentration, mutant cells revealed the elevated levels of transcripts of genes involved in the formation of Photosystem II (psbA, psbD, psbC, papoperon). This finding suggests that, in mutant cells, the PSII is sensitive to high concentrations of Mn 2? even at relatively low light intensity.
Biochemistry, 2002
Manganese is an essential micronutrient for many organisms. Because of its unique role in the water oxidizing activity of photosystem II, manganese is required for photosynthetic growth in plants and cyanobacteria. Here we report on the mechanism of manganese uptake in the cyanobacterium Synechocystis sp. PCC 6803. Cells grown in 9 µM manganese-containing medium accumulate up to 1 × 10 8 manganese atoms/cell, bound to the outer membrane (pool A). This pool could be released by EDTA treatment. Accumulation of manganese in pool A was energized by photosynthetic electron flow. Moreover, collapsing the membrane potential resulted in the immediate release of this manganese pool. The manganese in this pool is mainly Mn(II) in a six-coordinate distorted environment. A distinctly different pool of manganese, pool B (∼1.5 × 10 6 atoms/cell), could not be extracted by EDTA. Transport into pool B was light-independent and could be detected only under limiting manganese concentrations (1 nM). Evidently, manganese uptake in Synechocystis 6803 cells occurs in two steps. First, manganese accumulates in the outer membrane (pool A) in a membrane potential-dependent process. Next, manganese is transported through the inner membrane into pool B. We propose that pool A serves as a store that allows the cells to overcome transient limitations in manganese in the environment.
On the functional site of manganese in photosynthetic oxygen evolution
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1969
I. Restoration of Hill activity to illuminated Mn-deficient Euglena cultures is complete 4-6 h after Mn addition. 2. The maximum electron transfer rate at infinite light intensity is 2.5 times higher for MnR (reactivated) than for-Mn (deficient) chloroplasts, and the quantum efficiency is some 3 times greater. The fluorescence yield and quantum efficiency are likewise 4-5 fold higher in +Mn as against-Mn chloroplasts. 3. At 283°K, +Mn chloroplasts have a characteristic fluorescence maximum at 685 nm, while Mn chloroplasts have an additional shoulder at 693 nm. Reactivation of-Mn cells increases tile fluorescence emission of the isolated chloroplasts uniformly over the entire spectrum. 4. At 77°K, reactivation is accompanied by positive shifts in the fluorescence difference spectrum at 685, 7oo and 719 nm. The (+Mn)-(-Mn) spectrum is characterized in addition by a trough at about 73o nm. 5. The initial fluorescence yield induced by a weak measuring beam is 5o% higher in either-Mn chloroplasts or partially reactivated chloroplasts compared with +Mn chloroplasts. However, the variable excess fluorescence yield in strong illumination is almost absent in-Mn chloroplasts and is high in MnR and +Mn samples. 6. Hydroxylamine can donate electrons to Photosystem II, bypassing the-Mn block in electron flow and restoring high fluorescence yields. In cases of severe Mn deficiency, restoration of electron flow by hydroxylamine is only partial. 7. The results indicate a structural and a functional role for Mn in 02 evolution ; the latter, at least, residing in the span between water oxidation and the System II photoact. Abbreviations : APDC, ammonium pyrrolidine dithiocarbamate ; DCMU, 3-(3,4-dichlorophenyl)-i,i-dimethylurea; MES, 2-(N-morpholino)ethanesulfonic acid; TCPI, o-chlorophenolindo-2,6-dichlorophenol; TES, N-tris-(hydroxymethyl)nlethyl-2-aminoethanesulfonic acid.
The Plant Cell, 2016
In plants, algae, and cyanobacteria, photosystem II (PSII) catalyzes the light-driven oxidation of water. The oxygen-evolving complex of PSII is a Mn4CaO5 cluster embedded in a well-defined protein environment in thylakoid membranes. However, transport of manganese and calcium into the thylakoid lumen remains poorly understood. Here we show that Arabidopsis thaliana PHOTOSYNTHESIS AFFECTED MUTANT71 (PAM71) is an integral thylakoid membrane protein involved in Mn2+ and Ca2+ homeostasis in chloroplasts. This protein is required for normal operation of the oxygen-evolving complex (as evidenced by oxygen evolution rates) and for manganese incorporation. Manganese binding to PSII was severely reduced in pam71 thylakoids, particularly in PSII supercomplexes. In cation partitioning assays with intact chloroplasts, Mn2+ and Ca2+ ions were differently sequestered in pam71, with Ca2+ enriched in pam71 thylakoids relative to wild type. The changes in Ca2+ homeostasis were accompanied by an inc...
PLANT PHYSIOLOGY, 2011
Manganese (Mn) ions are essential for oxygen evolution activity in photoautotrophs. In this paper, we demonstrate the dynamic response of the photosynthetic apparatus to changes in Mn bioavailability in cyanobacteria. Cultures of the cyanobacterium Synechocystis PCC 6803 could grow on Mn concentrations as low as 100 nM without any observable effect on their physiology. Below this threshold, a decline in the photochemical activity of photosystem II (PSII) occurred, as evident by lower oxygen evolution rates, lower maximal photosynthetic yield of PSII values, and faster Q A reoxidation rates. In 77 K chlorophyll fluorescence spectroscopy, a peak at 682 nm was observed. After ruling out the contribution of phycobilisome and iron stress-induced IsiA proteins, this band was attributed to the accumulation of partially assembled PSII. Surprisingly, the increase in the 682-nm peak was paralleled by a decrease in the 720-nm peak, dominated by PSI fluorescence. The effect on PSI was confirmed by measurements of the P 700 photochemical activity. The loss of activity was the result of two processes: loss of PSI core proteins and changes in the organization of PSI complexes. Blue native-polyacrylamide gel electrophoresis analysis revealed a Mn limitation-dependent dissociation of PSI trimers into monomers. The sensitive range for changes in the organization of the photosynthetic apparatus overlaps with the range of Mn concentrations measured in natural environments. We suggest that the ability to manipulate PSI content and organization allows cyanobacteria to balance electron transport rates between the photosystems. At naturally occurring Mn concentrations, such a mechanism will provide important protection against light-induced damage.
Plant molecular biology, 2000
To investigate the interaction between the manganese-stabilizing protein (MSP) and cytochrome c-550 (cyt. c-550) of the photosystem II (PSII) complex in the cyanobacterium Synechocystis sp. PCC6803, three site-directed amino acid substitution mutants in MSP (MSP-D159N, MSP-R163L, MSP-D 159N/R 163L) were created by single and double amino acid substitution mutagenesis. The modified psbO genes encoding the mutants forms of MSP were used to transform a single-deletion mutant deltapsO strain lacking MSP as well as a double-deletion strain deltapsbO:deltapsbV lacking both MSP and cyt. c-550. The mutant forms of MSP were expressed in each case and all permitted autotrophic growth in strains expressing cyt. c-550. However, when the MSP mutations were introduced into a strain which lacks cyt. c-550 (deltapsbV), the two single amino acid substitution mutants (deltapsbV:MSP-D159N and deltapsbV:MSP-R 163L) failed to grow photoautotrophically. These strains exhibited coupled O2-evolving activity of 68-77% compared to the wild-type control using CO2 as an electron acceptor and maximal uncoupled O2-evolution rates of 42-57% using 2,6-dichloro-p-benzoquinone (DCBQ) as an artificial electron acceptor. Interestingly, when the two amino acid substitutions were together in the absence of cyt. c-550 (deltapsbV:MSP-D159N/R163L), the mutant grew photoautotrophically and the oxygen-evolving activities were higher than in the single mutants. This indicates that the MSP-D159N mutant suppresses the non-autotrophic phenotype of MSP-R163L (or vice versa) in the absence of cyt. c-550. The possibilities of a direct (ionic) or indirect interaction between D159 and R163 of MSP are discussed.
The Plant Cell
Mn is an essential component of the oxygen-evolving machinery of photosynthesis and is an essential cofactor of several important enzymes, such as Mn-superoxide dismutase and Mn-catalase. The availability of Mn in the environment varies, and little is known about the mechanisms for maintaining cytoplasmic Mn 2 ؉ ion homeostasis. Using a DNA microarray, we screened knockout libraries of His kinases and response regulators of Synechocystis sp PCC 6803 to identify possible participants in this process. We identified a His kinase, ManS, which might sense the extracellular concentration of Mn 2 ؉ ions, and a response regulator, ManR, which might regulate the expression of the mntCAB operon for the ABC-type transporter of Mn 2 ؉ ions. Furthermore, analysis with the DNA microarray and by reverse transcription PCR suggested that ManS produces a signal that activates ManR, which represses the expression of the mnt-CAB operon. At low concentrations of Mn 2 ؉ ions, ManS does not generate a signal, with resulting inactivation of ManR and subsequent expression of the mntCAB operon.
Plant Cell, 2002
Mn is an essential component of the oxygen-evolving machinery of photosynthesis and is an essential cofactor of several important enzymes, such as Mn-superoxide dismutase and Mn-catalase. The availability of Mn in the environment varies, and little is known about the mechanisms for maintaining cytoplasmic Mn 2 ؉ ion homeostasis. Using a DNA microarray, we screened knockout libraries of His kinases and response regulators of Synechocystis sp PCC 6803 to identify possible participants in this process. We identified a His kinase, ManS, which might sense the extracellular concentration of Mn 2 ؉ ions, and a response regulator, ManR, which might regulate the expression of the mntCAB operon for the ABC-type transporter of Mn 2 ؉ ions. Furthermore, analysis with the DNA microarray and by reverse transcription PCR suggested that ManS produces a signal that activates ManR, which represses the expression of the mnt-CAB operon. At low concentrations of Mn 2 ؉ ions, ManS does not generate a signal, with resulting inactivation of ManR and subsequent expression of the mntCAB operon.
The New phytologist, 2017
Manganese (Mn) is an essential constituent of photosystem II (PSII) and therefore indispensable for oxygenic photosynthesis. Very little is known about how Mn is transported, delivered and retained in photosynthetic cells. Recently, the thylakoid-localized transporter PAM71 has been linked to chloroplast Mn homeostasis in Arabidopsis thaliana. Here, we characterize the function of its homolog in Synechocystis (SynPAM71). We used a loss-of-function line (ΔSynPAM71), wild-type (WT) cells exposed to Mn stress and strains expressing a tagged variant of SynPAM71 to characterize the role of SynPAM71 in cyanobacterial Mn homeostasis. The ΔSynPAM71 strain displays an Mn-sensitive phenotype with reduced levels of chlorophyll and PSI accumulation, defects in PSII photochemistry and intracellular Mn enrichment, particularly in the thylakoid membranes. These effects are attributable to Mn toxicity, as very similar symptoms were observed in WT cells exposed to excess Mn. Moreover, CyanoP, which ...