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

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.

Download Full-text

Catalase Protects Biofilm of Staphylococcus aureus against Daptomycin Activity

Antibiotics ◽

10.3390/antibiotics10050511 ◽

2021 ◽

Vol 10 (5) ◽

pp. 511

Author(s):

Cristina El Haj ◽

Mads Lichtenberg ◽

Karen Leth Nielsen ◽

Thomas Bjarnsholt ◽

Peter Østrup Jensen

Keyword(s):

Reactive Oxygen Species ◽

Staphylococcus Aureus ◽

Bactericidal Activity ◽

Oxygen Species ◽

Bacterial Survival ◽

Wild Type ◽

Microtiter Plates ◽

In The Wild ◽

Ros Formation ◽

High Concentrations

Daptomycin is recommended for the treatment of Staphylococcus aureus infections due to its bactericidal activity. However, its mechanism of action is poorly understood. The involvement of reactive oxygen species (ROS) in the bactericidal activity of daptomycin has been proved against planktonic S. aureus, but not against the biofilm of S. aureus. Therefore, we evaluated if ROS contributes to the effect of daptomycin against biofilm of S. aureus. Biofilms of wild type, catalase deficient and daptomycin-resistant S. aureus strains were grown in microtiter-plates. After three days, the biofilms were exposed to daptomycin with or without thiourea in the presence of a ROS indicator. After overnight incubation, the amount of ROS and the percentage of surviving bacteria were determined. The bacterial survival was higher and the amount of ROS was lower in the wild type than in the catalase deficient biofilm, demonstrating a protective effect of catalase against daptomycin. The induction of cytotoxic ROS formation by daptomycin was verified by the addition of thiourea, which reduced the amount of ROS and protected the wild type biofilm against high concentrations of daptomycin. Accordingly, only the highest concentration of daptomycin reduced the bacterial survival and increased the ROS formation in the resistant biofilm. In conclusion, daptomycin induced the production of cytotoxic levels of endogenous ROS in S. aureus biofilm and the presence of catalase protected the biofilm against the lethality of the induced ROS.

Download Full-text

Perturbation of GABA Biosynthesis Links Cell Cycle to Control Arabidopsis thaliana Leaf Development

10.1101/2020.02.21.960393 ◽

2020 ◽

Author(s):

Yaxin Gong ◽

Han Yue ◽

Yu Xiang ◽

Guanghui Yu

Keyword(s):

Reactive Oxygen Species ◽

Leaf Development ◽

Cell Expansion ◽

Leaf Blade ◽

Aminobutyric Acid ◽

Oxygen Species ◽

Gaba Level ◽

Wild Type ◽

Blade Area ◽

In The Wild

AbstractTo investigate the molecular mechanism underlying increasing leaf area in γ-Aminobutyric acid (GABA) biosynthetic mutants, the first pair of true leaves of GABA biosynthetic mutants was measured. The results showed that the leaf blade area in GABA biosynthetic mutants was larger than that of the wild type to different extents, and the area of the leaf epidermal cells in mutants was larger than that of the wild type. DNA polyploid analysis showed that polyploid cells in GABA biosynthetic mutants were appearing earlier and more abundant than in the wild type. To check the correlation between cell size and endoreplication, the expression of factors involving endocycles, including D-type cyclin gene (CYCD3;1, CYCD3;2, CYCD3;3, and CYCD4;1) and kinase CKDA;1, were analysed by qRT-PCR. The results showed that CKDA;1 in GABA biosynthetic mutants was downregulated, and four types of CYCDs showed different expression patterns in different GABA biosynthetic mutants. Inconsistent with this result, for CCS52A (CELL CYCLE SWITCH 52A) (controlling the endocycle entry) in gad2 and gad1/gad2 mutants, the expression of CCS52A2 was significantly higher than that in the wild type. The expression of SIM (SIAMESE) and SMR (SIAMESE-RELATED), which inhibit kinase activity, were also upregulated compared with the control. To further study the possible potential relationship between GABA metabolism and endoreplication, we analysed the reactive oxygen species (ROS) levels in guard cells using ROS fluorescent probes. ROS levels were significantly higher in GABA biosynthetic mutants than the control. All results indicated that cyclin, the cyclin-dependent kinase, and its inhibitory protein were coordinated to participate in endoreplication control at the transcription level in the leaves of GABA biosynthetic mutant Arabidopsis.Contribution to the field statementγ-Aminobutyric acid (GABA) metabolic pathway plays a dual role in plant development. This research investigated the perturbation of GABA biosynthesis on Arabidopsis leave endoreplication for the first time. In the GABA biosynthetic mutants, many genes, participating in cell division regulation, are coordinately transcriptionally expressed to trigger the onset and maintenance of endoreplication, and this led to the cell expansion and the increase leaf blade area. However, this initiation of endoreplication links with the decrease of endogenous GABA level and the increase Reactive oxygen species (ROS). This may be a compensation mechanism to adapt to abnormal GABA level in plant leaf development. Present evidence provided hypothesized that the normal GABA level in plant leaf development plays a brake to inhibit the immature cell expansion and differentiation, and this negative regulation functions a guarantee mechanism to watchdog the normal leaf development. In all, this contribution provides an updated perspective on the role of GABA in plant development.

Download Full-text

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

Journal of Bacteriology ◽

10.1128/jb.186.10.3224-3229.2004 ◽

2004 ◽

Vol 186 (10) ◽

pp. 3224-3229 ◽

Cited By ~ 10

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.

Download Full-text

Production and scavenging of reactive oxygen species both affect reproductive success in male and female Drosophila melanogaster

Biogerontology ◽

10.1007/s10522-021-09922-1 ◽

2021 ◽

Author(s):

Biz R. Turnell ◽

Luisa Kumpitsch ◽

Klaus Reinhardt

Keyword(s):

Reactive Oxygen Species ◽

Drosophila Melanogaster ◽

Reactive Oxygen ◽

Cellular Aging ◽

Ros Production ◽

Oxygen Species ◽

Wild Type ◽

Ros Scavenging ◽

Respiratory Pathway ◽

Male And Female

AbstractSperm aging is accelerated by the buildup of reactive oxygen species (ROS), which cause oxidative damage to various cellular components. Aging can be slowed by limiting the production of mitochondrial ROS and by increasing the production of antioxidants, both of which can be generated in the sperm cell itself or in the surrounding somatic tissues of the male and female reproductive tracts. However, few studies have compared the separate contributions of ROS production and ROS scavenging to sperm aging, or to cellular aging in general. We measured reproductive fitness in two lines of Drosophila melanogaster genetically engineered to (1) produce fewer ROS via expression of alternative oxidase (AOX), an alternative respiratory pathway; or (2) scavenge fewer ROS due to a loss-of-function mutation in the antioxidant gene dj-1β. Wild-type females mated to AOX males had increased fecundity and longer fertility durations, consistent with slower aging in AOX sperm. Contrary to expectations, fitness was not reduced in wild-type females mated to dj-1β males. Fecundity and fertility duration were increased in AOX and decreased in dj-1β females, indicating that female ROS levels may affect aging rates in stored sperm and/or eggs. Finally, we found evidence that accelerated aging in dj-1β sperm may have selected for more frequent mating. Our results help to clarify the relative roles of ROS production and ROS scavenging in the male and female reproductive systems.

Download Full-text

Somatic production of reactive oxygen species does not predict its production in sperm cells across Drosophila melanogaster lines

BMC Research Notes ◽

10.1186/s13104-021-05550-7 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Biz R. Turnell ◽

Luisa Kumpitsch ◽

Anne-Cécile Ribou ◽

Klaus Reinhardt

Keyword(s):

Reactive Oxygen Species ◽

Drosophila Melanogaster ◽

Reactive Oxygen ◽

Future Research ◽

Ros Production ◽

Oxygen Species ◽

Loss Of Function ◽

Wild Type ◽

Ros Scavenging ◽

Transport Chain

Abstract Objective Sperm ageing has major evolutionary implications but has received comparatively little attention. Ageing in sperm and other cells is driven largely by oxidative damage from reactive oxygen species (ROS) generated by the mitochondria. Rates of organismal ageing differ across species and are theorized to be linked to somatic ROS levels. However, it is unknown whether sperm ageing rates are correlated with organismal ageing rates. Here, we investigate this question by comparing sperm ROS production in four lines of Drosophila melanogaster that have previously been shown to differ in somatic mitochondrial ROS production, including two commonly used wild-type lines and two lines with genetic modifications standardly used in ageing research. Results Somatic ROS production was previously shown to be lower in wild-type Oregon-R than in wild-type Dahomey flies; decreased by the expression of alternative oxidase (AOX), a protein that shortens the electron transport chain; and increased by a loss-of-function mutation in dj-1β, a gene involved in ROS scavenging. Contrary to predictions, we found no differences among these four lines in the rate of sperm ROS production. We discuss the implications of our results, the limitations of our study, and possible directions for future research.

Download Full-text

Control of reactive oxygen species (ROS) production through histidine kinases in Aspergillus nidulans under different growth conditions

FEBS Open Bio ◽

10.1016/j.fob.2014.01.003 ◽

2014 ◽

Vol 4 (1) ◽

pp. 90-95 ◽

Cited By ~ 6

Author(s):

Saki Hayashi ◽

Megumi Yoshioka ◽

Tetsuji Matsui ◽

Kensuke Kojima ◽

Masashi Kato ◽

...

Keyword(s):

Reactive Oxygen Species ◽

Aspergillus Nidulans ◽

Reactive Oxygen ◽

Growth Conditions ◽

Ros Production ◽

Oxygen Species ◽

Histidine Kinases

Download Full-text

MNB1 gene is involved in regulating the iron-deficiency stress response in Arabidopsis thaliana

10.21203/rs.3.rs-833563/v1 ◽

2021 ◽

Author(s):

Hui Song ◽

Feng Chen ◽

Xi Wu ◽

Min Hu ◽

Qingliu Geng ◽

...

Keyword(s):

Reactive Oxygen Species ◽

Arabidopsis Thaliana ◽

Normal Growth ◽

Developmental Changes ◽

Fe Deficiency ◽

Oxygen Species ◽

Mineral Element ◽

Wild Type ◽

Transcription Level ◽

Fe Uptake

Abstract Abstract Iron (Fe) is an indispensable mineral element for normal growth of plants. Fe deficiency induces a complex series of responses in plants, involving physiological and developmental changes, to increase Fe uptake from soil. However, the molecular mechanism involved in plant Fe-deficiency is not well understood. Here, we found that the MNB1 gene is involved in modulating Fe-deficiency response in Arabidopsis thaliana . The expression of MNB1 was inhabited by Fe-deficiency stress. Knockout of MNB1 led to enhanced Fe accumulation and tolerance, whereas the MNB1-overexpressing plants were sensitive to Fe-deficiency stress. Lower H 2 O 2 concentrations in mnb1 mutant plants were examined under Fe deficiency circumstances compared to wild-type. On the contray, higher H 2 O 2 concentrations were found in MNB1-overexpressing plants, which was adversely linked with malondialdehyde (MDA) concentrations. Furthermore, in mnb1 mutants, the transcription level of the Fe-uptake and translocation genes, FIT , IRT1 , FRO2 , Z IF , FRD3 , NAS4 , PYE and MYB72 , were considerably elevated during Fe-deficiency stress, resulting in higher Fe accumulation. Together, our findings show that the MNB1 gene negatively controls the Fe-deficiency response in Arabidopsis via modulating reactive oxygen species (ROS) levels and the ROS-mediated signaling pathway, thereby affecting the expression of Fe-uptake and translocation genes.

Download Full-text

Unveiling the Role Displayed by Penicillium digitatum PdMut3 Transcription Factor in Pathogen–Fruit Interaction

Journal of Fungi ◽

10.3390/jof7100828 ◽

2021 ◽

Vol 7 (10) ◽

pp. 828

Author(s):

Marta de Ramón-Carbonell ◽

Paloma Sánchez-Torres

Keyword(s):

Fungal Growth ◽

Dna Binding Protein ◽

Invasive Growth ◽

Wild Type ◽

Morphological Alterations ◽

Type Isolate ◽

In The Wild ◽

Expression Rate ◽

Regulatory Functions ◽

Null Mutants

Zn2Cys6 transcription factors are unique to fungi and are involved in different regulatory functions. In this study, we have identified the Penicillium digitatumPdMut3 gene, which encodes a putative Zn (II) 2Cys6 DNA-binding protein. Elimination of PdMut3 in Pd1 strain caused increased virulence during citrus infection. The transcription of the PdMut3 gene showed a higher expression rate during fungal growth and less transcription during fruit infection. Furthermore, the deletion of the gene in the wild-type isolate of P. digitatum did not produce any modification of the sensitivity to different fungicides, indicating that the gene is not associated with resistance to fungicides. In contrast, PdMut3 null mutants showed a reduction in growth in minimal media, which was associated with severe alterations in conidiophore development and morphological alterations of the hyphae. Mutants showed greater sensitivity to compounds that interfere with the cell wall and an invasive growth block. Thus, PdMut3 might have an indirect role in fungi virulence through metabolism and peroxisomes development.

Download Full-text

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

Journal of Bacteriology ◽

10.1128/jb.01036-07 ◽

2007 ◽

Vol 189 (21) ◽

pp. 7829-7840 ◽

Cited By ~ 30

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.

Download Full-text

Abstract 066: Cyclooxygenase-depended Signaling Via Thromboxane Prostanoid Receptors Mediates Endothelin-i Induced Ros Generation In Mesenteric Resistance Vessels From Mice Infused With Angiotensin Ii

Hypertension ◽

10.1161/hyp.64.suppl_1.066 ◽

2014 ◽

Vol 64 (suppl_1) ◽

Author(s):

Christopher S Wilcox ◽

Cheng Wang ◽

Dan Wang

Keyword(s):

Reactive Oxygen Species ◽

Angiotensin Ii ◽

Ros Generation ◽

Oxygen Species ◽

Ang Ii ◽

Wild Type ◽

Prostanoid Receptors ◽

Resistance Vessels ◽

Cox 2 ◽

Cox 1

Background: Angiotensin II (Ang II) increases reactive oxygen species (ROS) and contractions to thromboxane and endothelin-1 (ET-1). Therefore, we tested the hypothesis that cyclooxygenase (COX) and/or thromboxane-prostanoid receptors (TP-Rs) mediate enhanced ROS generations with ET-1 in Ang II-infused mice. Methods: ROS was assessed by urinary 8-isoprotane(8-Iso) excretion and ethedium : dihydroetheldium (DHE) in mesenteric resistance arterioles (MRAs) from wild type (+/+) and littermate COX-1 -/- or TP-R -/- mice infused with vehicle or angiotensin II (Ang II, 400 ng/kg/min for 14 days) (n=6/ group, mean ±SEM). Results: Ang II infusion increased excretion (ng/mg creatine) of TxB 2 (1.3±0.1±1.0±0.1 in COX-1 +/+ mice and 1.9±0.1 vs 1.2±0.1 in TP-R +/+ mice, all P<0.05) and 8-Iso (2.1±0.2 vs 1.4±0.1 in COX-1 +/+ mice and 2.2±0.1 vs 1.4±0.2 in TP-R +/+ mice, all P<0.05) but not in COX-1 -/- or TP-R -/- mice. Ang II enhanced ROS generation (Δunit) with 10 -7 M ET-1 in MRAs from both +/+ mouse genotypes (1.7±0.2 vs 0.1±0.1 in COX-1 +/+ mice and 3.2±0.3 vs 0.1±0.1 in TP-R +/+ mice, all P<0.01). However, this increase in ROS was fully prevented in TP-R-/- mouse vessels (0.3±0.2 vs 0.2±0.1, NS) and in COX-1 +/+ mouse vessels after combined blockade of COX-1( 10 -5 M SC-560) and -2 (paracoxib 10 -5 M) (0.2±0.1 vs 0.1±0.1, NS) and in COX-1 -/- mouse vessels after paracoxib (0.2±0.1 vs 0.2±0.2, NS). Increased ROS generation was only partially prevented in COX-1 -/- mouse vessels (0.5±0.1 vs 0.2±0.2, P<0.05) or in COX-1 +/+ mouse vessels after blockade of COX-1 ( 0.7±0.1 vs 0.1±0.1, NS) or COX-2 (1.0±0.1 vs 0.1±0.1,P<0.05). Conclusions: Increased ROS generation with ET-1 in microvessels from Ang II infused mice depends on products of both COX-1 and -2 that activate TP-Rs. Thus, combined blockade of COX-1 and -2 or TP-Rs may prevent vascular ROS and its many complications during increased Ang II and ET-1, such as hypertension, hypoxia or shock.

Download Full-text