scholarly journals Nitrite-Responsive Activation of the Nitrate Assimilation Operon in Cyanobacteria Plays an Essential Role in Up-Regulation of Nitrate Assimilation Activities under Nitrate-Limited Growth Conditions

2004 ◽  
Vol 186 (10) ◽  
pp. 3224-3229 ◽  
Author(s):  
Makiko Aichi ◽  
Shin-Ichi Maeda ◽  
Kazuhiro Ichikawa ◽  
Tatsuo Omata
Keyword(s):  
Enzyme Activities ◽  
Nitrate Assimilation ◽  
Growth Conditions ◽  
Activity Levels ◽  
Wild Type ◽  
Limited Growth ◽  
Physiological Importance ◽  
In The Wild ◽  
Operon Expression ◽  
Pcc 7942

ABSTRACT NtcB of the cyanobacterium Synechococcus elongatus strain PCC 7942 is a LysR family protein that enhances expression of the nitrate assimilation operon (nirA operon) in response to the presence of nitrite, an intermediate of assimilatory nitrate reduction. Inactivation of ntcB in this cyanobacterium specifically abolishes the nitrite responsiveness of nirA operon expression, but under nitrate-replete conditions (wherein negative feedback by intracellularly generated ammonium prevails over the positive effect of nitrite) activity levels of the nitrate assimilation enzymes are marginally higher in the wild-type cells than in the mutant cells, raising the issue of whether the nitrite-promoted regulation has physiological importance. On the other hand, the strains carrying ntcB expressed much higher nitrate assimilation enzyme activities under nitrate-limited growth conditions than under nitrate-replete conditions whereas the ntcB-deficient strains showed levels of the enzyme activities lower than those seen under the nitrate-replete conditions. Although the ntcB mutant maintained a constant cell population in a nitrate-limited chemostat when grown as a single culture, it was diluted at a rate expected for nondividing cells when mixed with the wild-type cells and subjected to nitrate limitation in the chemostat culture system. These results demonstrated that the nitrite-promoted activation of the nitrate assimilation operon is essential for up-regulation of the nitrate assimilation activities under the conditions of nitrate limitation and for competitive utilization of nitrate.

scholarly journals Redox crisis underlies conditional light–dark lethality in cyanobacterial mutants that lack the circadian regulator, RpaA

2017 ◽  
Vol 114 (4) ◽  
pp. E580-E589 ◽  
Author(s):  
Spencer Diamond ◽  
Benjamin E. Rubin ◽  
Ryan K. Shultzaberger ◽  
You Chen ◽  
Chase D. Barber ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Response Regulator ◽  
Mechanistic Explanation ◽  
Growth Conditions ◽  
Oxygen Species ◽  
Wild Type ◽  
Profound Influence ◽  
In The Wild ◽  
Pcc 7942 ◽  
Null Mutants

Cyanobacteria evolved a robust circadian clock, which has a profound influence on fitness and metabolism under daily light–dark (LD) cycles. In the model cyanobacterium Synechococcus elongatus PCC 7942, a functional clock is not required for diurnal growth, but mutants defective for the response regulator that mediates transcriptional rhythms in the wild-type, regulator of phycobilisome association A (RpaA), cannot be cultured under LD conditions. We found that rpaA-null mutants are inviable after several hours in the dark and compared the metabolomes of wild-type and rpaA-null strains to identify the source of lethality. Here, we show that the wild-type metabolome is very stable throughout the night, and this stability is lost in the absence of RpaA. Additionally, an rpaA mutant accumulates excessive reactive oxygen species (ROS) during the day and is unable to clear it during the night. The rpaA-null metabolome indicates that these cells are reductant-starved in the dark, likely because enzymes of the primary nighttime NADPH-producing pathway are direct targets of RpaA. Because NADPH is required for processes that detoxify ROS, conditional LD lethality likely results from inability of the mutant to activate reductant-requiring pathways that detoxify ROS when photosynthesis is not active. We identified second-site mutations and growth conditions that suppress LD lethality in the mutant background that support these conclusions. These results provide a mechanistic explanation as to why rpaA-null mutants die in the dark, further connect the clock to metabolism under diurnal growth, and indicate that RpaA likely has important unidentified functions during the day.

scholarly journals Role of Sigma Factors in Controlling Global Gene Expression in Light/Dark Transitions in the Cyanobacterium Synechocystis sp. Strain PCC 6803

2007 ◽  
Vol 189 (21) ◽  
pp. 7829-7840 ◽  
Author(s):  
Tina C. Summerfield ◽  
Louis A. Sherman
Keyword(s):  
Gene Expression ◽  
Global Gene Expression ◽  
Growth Conditions ◽  
Day Length ◽  
Regulation Of Transcription ◽  
Wild Type ◽  
Protein Levels ◽  
In The Wild ◽  
Altered Gene ◽  
Pcc 6803

ABSTRACT We report on differential gene expression in the cyanobacterium Synechocystis sp. strain PCC 6803 after light-dark transitions in wild-type, ΔsigB, and ΔsigD strains. We also studied the effect of day length in the presence of glucose on a ΔsigB ΔsigE mutant. Our results indicated that the absence of SigB or SigD predominately altered gene expression in the dark or in the light, respectively. In the light, approximately 350 genes displayed transcript levels in the ΔsigD strain that were different from those of the wild type, with over 200 of these up-regulated in the mutant. In the dark, removal of SigB altered more than 150 genes, and the levels of 136 of these were increased in the mutant compared to those in the wild type. The removal of both SigB and SigE had a major impact on gene expression under mixotrophic growth conditions and resulted in the inability of cells to grow in the presence of glucose with 8-h light and 16-h dark cycles. Our results indicated the importance of group II σ factors in the global regulation of transcription in this organism and are best explained by using the σ cycle paradigm with the stochastic release model described previously (R. A. Mooney, S. A. Darst, and R. Landick, Mol. Cell 20:335-345, 2005). We combined our results with the total protein levels of the σ factors in the light and dark as calculated previously (S. Imamura, S. Yoshihara, S. Nakano, N. Shiozaki, A. Yamada, K. Tanaka, H. Takahashi, M. Asayama, and M. Shirai, J. Mol. Biol. 325:857-872, 2003; S. Imamura, M. Asayama, H. Takahashi, K. Tanaka, H. Takahashi, and M. Shirai, FEBS Lett. 554:357-362, 2003). Thus, we concluded that the control of global transcription is based on the amount of the various σ factors present and able to bind RNA polymerase.

scholarly journals Involvement of BGLU30 in Glucosinolate Catabolism in the Arabidopsis Leaf under Dark Conditions

2020 ◽  
Vol 61 (6) ◽  
pp. 1095-1106 ◽  
Author(s):  
Tomomi Morikawa-Ichinose ◽  
Daisuke Miura ◽  
Liu Zhang ◽  
Sun-Ju Kim ◽  
Akiko Maruyama-Nakashita
Keyword(s):  
Mass Spectrometry Imaging ◽  
Distribution Patterns ◽  
Growth Conditions ◽  
Ionization Mass ◽  
Laser Desorption Ionization ◽  
Light Conditions ◽  
Wild Type ◽  
In The Wild ◽  
Unique Distribution ◽  
Dark Conditions

Abstract Glucosinolates (GSLs) are secondary metabolites that play important roles in plant defense and are suggested to act as storage compounds. Despite their important roles, metabolic dynamics of GSLs under various growth conditions remain poorly understood. To determine how light conditions influence the levels of different GSLs and their distribution in Arabidopsis leaves, we visualized the GSLs under different light conditions using matrix-assisted laser desorption/ionization mass spectrometry imaging. We observed the unique distribution patterns of each GSL in the inner regions of leaves and marked decreases under darkness, indicating light conditions influenced GSL metabolism. GSLs are hydrolyzed by a group of ß-glucosidase (BGLU) called myrosinase. Previous transcriptome data for GSL metabolism under light and dark conditions have revealed the highly induced expression of BGLU30, one of the putative myrosinases, which is also annotated as Dark INducible2, under darkness. Impairment of the darkness-induced GSL decrease in the disruption mutants of BGLU30, bglu30, indicated that BGLU30 mediated GSL hydrolysis under darkness. Based on the GSL profiles in the wild-type and bglu30 leaves under both conditions, short-chain GSLs were potentially preferable substrates for BGLU30. Our findings provide an effective way of visualizing GSL distribution in plants and highlighted the carbon storage GSL function.

scholarly journals Role of Acinetobacter baylyi Crc in Catabolite Repression of Enzymes for Aromatic Compound Catabolism

2009 ◽  
Vol 191 (8) ◽  
pp. 2834-2842 ◽  
Author(s):  
Tina Zimmermann ◽  
Tobias Sorg ◽  
Simone Yasmin Siehler ◽  
Ulrike Gerischer
Keyword(s):  
Catabolite Repression ◽  
Carbon Sources ◽  
Transcript Abundance ◽  
Growth Conditions ◽  
Wild Type ◽  
Acinetobacter Baylyi ◽  
Transcript Stability ◽  
Key Enzyme ◽  
In The Wild ◽  
First Time

ABSTRACT Here, we describe for the first time the Crc (catabolite repression control) protein from the soil bacterium Acinetobacter baylyi. Expression of A. baylyi crc varied according to the growth conditions. A strain with a disrupted crc gene showed the same growth as the wild type on a number of carbon sources. Carbon catabolite repression by acetate and succinate of protocatechuate 3,4-dioxygenase, the key enzyme of protocatechuate breakdown, was strongly reduced in the crc strain, whereas in the wild-type strain it underwent strong catabolite repression. This strong effect was not based on transcriptional regulation because the transcription pattern of the pca-qui operon (encoding protocatechuate 3,4-dioxygenase) did not reflect the derepression in the absence of Crc. pca-qui transcript abundance was slightly increased in the crc strain. Lack of Crc dramatically increased the mRNA stability of the pca-qui transcript (up to 14-fold), whereas two other transcripts (pobA and catA) remained unaffected. p-Hydroxybenzoate hydroxylase activity, encoded by pobA, was not significantly different in the absence of Crc, as protocatechuate 3,4-dioxygenase was. It is proposed that A. baylyi Crc is involved in the determination of the transcript stability of the pca-qui operon and thereby effects catabolite repression.

scholarly journals The NtcA-Regulated amtB Gene Is Necessary for Full Methylammonium Uptake Activity in the Cyanobacterium Synechococcus elongatus

2007 ◽  
Vol 189 (21) ◽  
pp. 7791-7798 ◽  
Author(s):  
Javier Paz-Yepes ◽  
Antonia Herrero ◽  
Enrique Flores
Keyword(s):  
Synechococcus Elongatus ◽  
Nitrogen Deprivation ◽  
Wild Type ◽  
Noticeable Effect ◽  
Unicellular Cyanobacterium ◽  
Net Uptake ◽  
In The Wild ◽  
Uptake Activity ◽  
Step Down ◽  
Pcc 7942

ABSTRACT The Amt proteins constitute a ubiquitous family of transmembrane ammonia channels that permit the net uptake of ammonium by cells. In many organisms, there is more than one amt gene, and these genes are subjected to nitrogen control. The mature Amt protein is a homo- or heterooligomer of three Amt subunits. We previously characterized an amt1 gene in the unicellular cyanobacterium Synechococcus elongatus strain PCC 7942. In this work, we describe the presence in this organism of a second amt gene, amtB, which encodes a protein more similar to the bacterial AmtB proteins than to any other characterized cyanobacterial Amt protein. The expression of amtB took place in response to nitrogen step-down, required the NtcA transcription factor, and occurred parallel to the expression of amt1. However, the transcript levels of amtB measured after 2 h of nitrogen deprivation were about 100-fold lower than those of amt1. An S. elongatus amtB insertional mutant exhibited an activity for uptake of [14C]methylammonium that was about 55% of that observed in the wild type, but inactivation of amtB had no noticeable effect on the uptake of ammonium when it was supplied at a concentration of 100 μM or more. Because an S. elongatus amt1 mutant is essentially devoid of [14C]methylammonium uptake activity, the mature Amt transporter is functional in the absence of AmtB subunits but not in the absence of Amt1 subunits. However, the S. elongatus amtB mutant could not concentrate [14C]methylammonium within the cells to the same extent as the wild type. Therefore, AmtB is necessary for full methylammonium uptake activity in S. elongatus.

scholarly journals Alanine Dehydrogenase Activity Is Required for Adequate Progression of Phycobilisome Degradation during Nitrogen Starvation in Synechococcus elongatus PCC 7942

2006 ◽  
Vol 188 (14) ◽  
pp. 5258-5265 ◽  
Author(s):  
Roxane Lahmi ◽  
Eleonora Sendersky ◽  
Alexander Perelman ◽  
Martin Hagemann ◽  
Karl Forchhammer ◽  
...  
Keyword(s):  
Dehydrogenase Activity ◽  
Cellular Response ◽  
Nitrogen Starvation ◽  
Synechococcus Elongatus ◽  
Wild Type ◽  
Sulfur Starvation ◽  
Alanine Dehydrogenase ◽  
In The Wild ◽  
Synechococcus Elongatus Pcc 7942 ◽  
Pcc 7942

ABSTRACT Degradation of the cyanobacterial light-harvesting antenna, the phycobilisome, is a general acclimation response that is observed under various stress conditions. In this study we identified a novel mutant of Synechococcus elongatus PCC 7942 that exhibits impaired phycobilisome degradation specifically during nitrogen starvation, unlike previously described mutants, which exhibit aberrant degradation under nitrogen, sulfur, and phosphorus starvation conditions. The phenotype of the new mutant, AldΩ, results from inactivation of ald (encoding alanine dehydrogenase). AldΩ is deficient in transcription induction of a number of genes during nitrogen starvation. These genes include the “general nutrient stress-related” genes, nblA and nblC, the products of which are essential for phycobilisome degradation. Furthermore, transcripts of several specific nitrogen-responsive genes accumulate at lower levels in AldΩ than in the wild-type strain. In contrast, ald inactivation did not decrease the accumulation of transcripts during sulfur starvation. Transcription of ald is induced upon nitrogen starvation, which is consistent with the ability of wild-type cells to maintain a low cellular content of alanine under these conditions. Unlike wild-type cells, AldΩ accumulates alanine upon nitrogen starvation. Our analyses suggest that alanine dehydrogenase activity is necessary for an adequate cellular response to nitrogen starvation. Decomposition of alanine may be required to provide a sufficient amount of ammonia. Furthermore, the accumulated alanine, or a related metabolite, may interfere with the cues that modulate acclimation during nitrogen starvation. Taken together, our results provide novel information regarding cellular responses to nitrogen starvation and suggest that mechanisms related to nitrogen-specific responses are involved in modulation of a general acclimation process.

scholarly journals Genetically engineered mutant of the cyanobacterium Synechococcus PCC 7942 defective in nitrate transport

1989 ◽  
Vol 86 (17) ◽  
pp. 6612-6616 ◽  
Author(s):  
Tatsuo Omata ◽  
Masayuki Ohmori ◽  
Nobuyuki Arai ◽  
Teruo Ogawa
Keyword(s):  
Nitrate Concentration ◽  
Growth Conditions ◽  
Genetically Engineered ◽  
Nitrate Transport ◽  
Major Protein ◽  
Wild Type ◽  
Synechococcus Pcc 7942 ◽  
High Concentrations ◽  
Nitrate And Nitrite ◽  
Pcc 7942

Nitrate-grown cells of Synechococcus PCC 7942 (Anacystis nidulans R2) contain a 45-kDa protein as a major protein in the cytoplasmic membrane but ammonium-grown cells lack it. A mutant (M45) was constructed by inactivating the gene encoding the 45-kDa protein. M45 did not grow under low concentrations of nitrate but high concentrations of nitrate could support its growth, with the optimal concentration being 40-70 mM. The growth rate of M45 was as high as that of the wild-type cells when ammonium was the nitrogen source. The 45-kDa protein was absent in M45 irrespective of the growth conditions. The activities of nitrate and nitrite reductases were higher in M45 than in wild type. The rate of nitrate-dependent O2 evolution in wild type measured in the presence of L-methionine D,L-sulfoximine and D,L-glyceraldehyde showed saturation kinetics with respect to nitrate concentration in the external medium. The nitrate concentration required to produce half the maximal rate was 1 μM. In M45, the rate of nitrate-dependent O2 evolution was nearly zero at nitrate concentrations <1 mM and was linearly increased as the concentration increased. The presumed absence of nitrate transport in M45 demonstrated by these results suggested that the 45-kDa protein is a nitrate transporter.

scholarly journals Role of NtcB in Activation of Nitrate Assimilation Genes in the Cyanobacterium Synechocystis sp. Strain PCC 6803

2001 ◽  
Vol 183 (20) ◽  
pp. 5840-5847 ◽  
Author(s):  
Makiko Aichi ◽  
Nobuyuki Takatani ◽  
Tatsuo Omata
Keyword(s):  
Nitrate Assimilation ◽  
Ammonium Assimilation ◽  
Dependent Manner ◽  
Wild Type ◽  
Transcriptional Enhancer ◽  
Genes Encoding ◽  
Different Strains ◽  
Pcc 7942 ◽  
Pcc 6803

ABSTRACT In Synechocystis sp. strain PCC 6803, the genes encoding the proteins involved in nitrate assimilation are organized into two transcription units,nrtABCD-narB and nirA, the expression of which was repressed by ammonium and induced by inhibition of ammonium assimilation, suggesting involvement of NtcA in the transcriptional regulation. Under inducing conditions, expression of the two transcription units was enhanced by nitrite, suggesting regulation by NtcB, the nitrite-responsive transcriptional enhancer we previously identified in Synechococcus sp. strain PCC 7942. The slr0395 gene, which encodes a protein 47% identical to Synechococcus NtcB, was identified as theSynechocystis ntcB gene, on the basis of the inability of an slr0395 mutant to rapidly accumulate the transcripts of the nitrate assimilation genes upon induction and to respond to nitrite. While Synechococcus NtcB strictly requires nitrite for its action, Synechocystis NtcB enhanced transcription significantly even in the absence of nitrite. Whereas the Synechococcus ntcB mutant expresses the nitrate assimilation genes to a significant level in an NtcA-dependent manner, the Synechocystis ntcB mutant showed only low-level expression of the nitrate assimilation genes, indicating that NtcA by itself cannot efficiently promote expression of these genes inSynechocystis. Activities of the nitrate assimilation enzymes in the Synechocystis ntcB mutant were consequently low, being 40 to 50% of the wild-type level, and the cells grew on nitrate at a rate approximately threefold lower than that of the wild-type strain. These results showed that the contribution of NtcB to the expression of nitrate assimilation capability varies considerably among different strains of cyanobacteria.

Multiple isoacceptor forms of several transfer ribonucleic acids in a mutant yeast strain

1978 ◽  
Vol 56 (1) ◽  
pp. 51-59 ◽  
Author(s):  
J. B. Bell ◽  
K. Bruce Jacobson ◽  
Lee R. Shugart
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Growth Conditions ◽  
Wild Type ◽  
Reverse Phase ◽  
Ribonucleic Acids ◽  
Multiple Peaks ◽  
Single Form ◽  
In The Wild ◽  
Wild Type Yeast

By use of reverse phase 5 chromatography, a strain of Saccharomyces cerevisiae (XB109-5B) has been shown to exhibit multiple isoaccepting forms for several of the transfer ribonucleic acids (tRNAs). This is in contrast with a standard wild-type strain where only one acceptor is found for each tRNA studied. Multiple peaks for tRNATyr, tRNAPhe, tRNASer, and tRNAVal have been detected for strain XB109-5B. However, the observation of multiple isoacceptors cannot be extended to all tRNAs in this strain since tRNAAsp appears as a single form that is the same as in the wild type. The appearance of multiple peaks was found to depend on the growth conditions of the cells. The tRNA profiles of XB109-5B that was grown rapidly with vigorous aeration differed the most from profiles of comparably grown wild-type yeast, whereas tRNA from this mutant, grown without shaking or supplementary aeration, appeared the same as the wild type. The minor nucleoside composition of the isoacceptors of tRNAPhe was obtained.

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