scholarly journals Mitochondrial DNA Instability in Cells Lacking Aconitase Correlates with Iron Citrate Toxicity

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Muhammad A. Farooq ◽  
Tammy M. Pracheil ◽  
Zhejun Dong ◽  
Fei Xiao ◽  
Zhengchang Liu
Keyword(s):  
Mitochondrial Dna ◽  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Alternative Mechanism ◽  
Iron Citrate ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Citrate Accumulation ◽  
Mitochondrial Dna Instability ◽  
Mutant Cells

Aconitase, the second enzyme of the tricarboxylic acid cycle encoded byACO1in the budding yeastSaccharomyces cerevisiae, catalyzes the conversion of citrate to isocitrate.aco1Δ results in mitochondrial DNA (mtDNA) instability. It has been proposed that Aco1 binds to mtDNA and mediates its maintenance. Here we propose an alternative mechanism to account for mtDNA loss inaco1Δ mutant cells. We found thataco1Δ activated the RTG pathway, resulting in increased expression of genes encoding citrate synthase. By deletingRTG1,RTG3, or genes encoding citrate synthase, mtDNA instability was prevented inaco1Δ mutant cells. Increased activity of citrate synthase leads to iron accumulation in the mitochondria. Mutations inMRS3andMRS4, encoding two mitochondrial iron transporters, also prevented mtDNA loss due toaco1Δ. Mitochondria are the main source of superoxide radicals, which are converted to H2O2through two superoxide dismutases, Sod1 and Sod2. H2O2in turn reacts with Fe2+to generate very active hydroxyl radicals. We found that loss of Sod1, but not Sod2, prevents mtDNA loss inaco1Δ mutant cells. We propose that mtDNA loss inaco1Δ mutant cells is caused by the activation of the RTG pathway and subsequent iron citrate accumulation and toxicity.

scholarly journals Reduced Histone Expression or a Defect in Chromatin Assembly Induces Respiration

2016 ◽  
Vol 36 (7) ◽  
pp. 1064-1077 ◽  
Author(s):  
Luciano Galdieri ◽  
Tiantian Zhang ◽  
Daniella Rogerson ◽  
Ales Vancura
Keyword(s):  
Mitochondrial Dna ◽  
Chromatin Structure ◽  
Glucose Repression ◽  
Atp Synthesis ◽  
Tca Cycle ◽  
Nucleosome Assembly ◽  
Content Type ◽  
Copy Numbers ◽  
Expression Of Genes ◽  
Genes Encoding

Regulation of mitochondrial biogenesis and respiration is a complex process that involves several signaling pathways and transcription factors as well as communication between the nuclear and mitochondrial genomes. Here we show that decreased expression of histones or a defect in nucleosome assembly in the yeastSaccharomyces cerevisiaeresults in increased mitochondrial DNA (mtDNA) copy numbers, oxygen consumption, ATP synthesis, and expression of genes encoding enzymes of the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS). The metabolic shift from fermentation to respiration induced by altered chromatin structure is associated with the induction of the retrograde (RTG) pathway and requires the activity of the Hap2/3/4/5p complex as well as the transport and metabolism of pyruvate in mitochondria. Together, our data indicate that altered chromatin structure relieves glucose repression of mitochondrial respiration by inducing transcription of the TCA cycle and OXPHOS genes carried by both nuclear and mitochondrial DNA.

scholarly journals Evaluation of the role of Rhizobacteria in controlling root knot nematode (RKN) infection in Lycopersicon esculentum plants by modulation in the secondary metabolite profiles

AoB Plants ◽  
2019 ◽  
Author(s):  
Kanika Khanna ◽  
Vijay Lakshmi Jamwal ◽  
Anket Sharma ◽  
Sumit G Gandhi ◽  
Puja Ohri ◽  
...  
Keyword(s):  
Phenolic Compounds ◽  
Citrate Synthase ◽  
Fumarate Hydratase ◽  
Malate Synthase ◽  
Plant Pigments ◽  
Root Knot Nematode ◽  
Expression Of Genes ◽  
Burkholderia Gladioli ◽  
Genes Encoding ◽  
Negative Impacts

Abstract Environmental stress imposes negative impacts on the growth and development of the crop plants. The present study was designed to assess the effect of PGPR (Pseudomonas aeruginosa and Burkholderia gladioli) on plant pigments and phenolic compounds in 10-days-old root knot nematode (RKN)-infected Lycopersiconesculentum seedlings. The levels of different osmoprotectants and organic acids were also evaluated in nematode-infected L. esculentum seedlings. Our results revealed that nematode-infected seedlings had reduced levels of plant pigments(chlorophyll (70.5%), carotenoids (64.8%), and xanthophylls (34.3%)) and enhanced levels of phenolic compounds(total phenols (40.3%), flavonoids (80.9%), anthocyanins (28.9%), and polyphenols (366.1%)), osmoprotectants(total osmolytes (15.3%), total carbohydrates (54.9%), reducing sugars (45.3%), trehalose (94.5%), glycine betaine (59.01%) and proline (69.6%) and (citric acid (28.4%), fumaric acid (18.16%), succinic acid (179.9%), and malic acid (21.7%)). The levels of these metabolites increased after inoculation with P. aeruginosa and B. gladioli. The expression of genes encoding different enzymes pertaining to phenols and organic acid metabolism were also studied. The expression of genes was elevated in nematode-infected plants i.e. CHS (chalcone synthase) by 1.32 folds, PAL (phenylalanine ammonia lyase) by 1.16 folds, CS (citrate synthase)1.6 folds, SUCLG1 (succinyl Co-A ligase) by 1.19 folds, SDH (succinate dehydrogenase) by 1.92 folds, FH (fumarate hydratase) by 2.4 foldsand malate synthase (MS) by 1.26 folds and further upregulated after PGPR inoculation. This study demonstrates the importance of PGPR in managing nematode infection in plants through alteration in the synthesis of different secondary metabolites in plants.

scholarly journals Nucleotide sequence encoding the iron-sulphur protein subunit of the succinate dehydrogenase of Escherichia coli

1984 ◽  
Vol 223 (2) ◽  
pp. 507-517 ◽  
Author(s):  
M G Darlison ◽  
J R Guest
Keyword(s):  
Nucleotide Sequence ◽  
Succinate Dehydrogenase ◽  
Structural Gene ◽  
Base Pair ◽  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Regulatory Elements ◽  
Protein Subunit ◽  
Genes Encoding ◽  
Oxoglutarate Dehydrogenase

The nucleotide sequence of a 961 base-pair segment of DNA containing the sdhB gene, which encodes the iron-sulphur protein subunit of the E. coli succinate dehydrogenase, has been determined. The sdhB structural gene comprises 711 base pairs (237 codons, excluding the translational initiator and terminator). It is separated by a 15 base-pair intergenic region from the preceding flavoprotein gene (sdhA) and is the distal gene of an operon that also includes genes (sdhC and D) encoding two hydrophobic subunits, sdhCDAB. The distal end of the sdh operon is linked to the 2-oxoglutarate dehydrogenase gene (sucA) by a complex region of dyad symmetry that is homologous with several potential intercistronic regulatory elements or transcriptional attenuators. The sdhB structural gene encodes a polypeptide of Mr26637 that is strikingly homologous with the iron-sulphur protein subunit of fumarate reductase (38% identity, increasing to 58% when conservative changes are included). Both subunits contain 11 cysteine residues, 10 being conserved in three clusters resembling those found in ferredoxins. This work completes the sequence of a 9897 base-pair segment of DNA containing seven tricarboxylic acid cycle genes encoding three enzymes or enzyme complexes, citrate synthase (gltA), succinate dehydrogenase (sdh), and the 2-oxoglutarate dehydrogenase complex (suc), that are organized thus: gltA-sdhCDAB-sucAB.

scholarly journals Saccharomyces cerevisiae Engineered for Xylose Metabolism Exhibits a Respiratory Response

2004 ◽  
Vol 70 (11) ◽  
pp. 6816-6825 ◽  
Author(s):  
Yong-Su Jin ◽  
Jose M. Laplaza ◽  
Thomas W. Jeffries
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Tricarboxylic Acid Cycle ◽  
Pentose Phosphate ◽  
Oxygen Limitation ◽  
Sugar Uptake ◽  
Xylose Utilization ◽  
Xylose Metabolism ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Native Strains

ABSTRACT Native strains of Saccharomyces cerevisiae do not assimilate xylose. S. cerevisiae engineered for d-xylose utilization through the heterologous expression of genes for aldose reductase (XYL1), xylitol dehydrogenase (XYL2), and d-xylulokinase (XYL3 or XKS1) produce only limited amounts of ethanol in xylose medium. In recombinant S. cerevisiae expressing XYL1, XYL2, and XYL3, mRNA transcript levels for glycolytic, fermentative, and pentose phosphate enzymes did not change significantly on glucose or xylose under aeration or oxygen limitation. However, expression of genes encoding the tricarboxylic acid cycle, respiration enzymes (HXK1, ADH2, COX13, NDI1, and NDE1), and regulatory proteins (HAP4 and MTH1) increased significantly when cells were cultivated on xylose, and the genes for respiration were even more elevated under oxygen limitation. These results suggest that recombinant S. cerevisiae does not recognize xylose as a fermentable carbon source and that respiratory proteins are induced in response to cytosolic redox imbalance; however, lower sugar uptake and growth rates on xylose might also induce transcripts for respiration. A petite respiration-deficient mutant (ρ�) of the engineered strain produced more ethanol and accumulated less xylitol from xylose. It formed characteristic colonies on glucose, but it did not grow on xylose. These results are consistent with the higher respiratory activity of recombinant S. cerevisiae when growing on xylose and with its inability to grow on xylose under anaerobic conditions.

scholarly journals Two Pathway-Specific Transcriptional Regulators, PltR and PltZ, Coordinate Autoinduction of Pyoluteorin in Pseudomonas protegens Pf-5

2021 ◽  
Vol 9 (7) ◽  
pp. 1489
Author(s):  
Qing Yan ◽  
Mary Liu ◽  
Teresa Kidarsa ◽  
Colin P. Johnson ◽  
Joyce E. Loper
Keyword(s):  
Gene Cluster ◽  
Transcriptional Regulator ◽  
Transcriptional Regulators ◽  
Soil Bacterium ◽  
Antibiotic Biosynthesis ◽  
Environmental Cues ◽  
Alternative Mechanism ◽  
Pseudomonas Spp ◽  
Expression Of Genes ◽  
Genes Encoding

Antibiotic biosynthesis by microorganisms is commonly regulated through autoinduction, which allows producers to quickly amplify the production of antibiotics in response to environmental cues. Antibiotic autoinduction generally involves one pathway-specific transcriptional regulator that perceives an antibiotic as a signal and then directly stimulates transcription of the antibiotic biosynthesis genes. Pyoluteorin is an autoregulated antibiotic produced by some Pseudomonas spp. including the soil bacterium Pseudomonas protegens Pf-5. In this study, we show that PltR, a known pathway-specific transcriptional activator of pyoluteorin biosynthesis genes, is necessary but not sufficient for pyoluteorin autoinduction in Pf-5. We found that pyoluteorin is perceived as an inducer by PltZ, a second pathway-specific transcriptional regulator that directly represses the expression of genes encoding a transporter in the pyoluteorin gene cluster. Mutation of pltZ abolished the autoinducing effect of pyoluteorin on the transcription of pyoluteorin biosynthesis genes. Overall, our results support an alternative mechanism of antibiotic autoinduction by which the two pathway-specific transcriptional regulators PltR and PltZ coordinate the autoinduction of pyoluteorin in Pf-5. Possible mechanisms by which PltR and PltZ mediate the autoinduction of pyoluteorin are discussed.

scholarly journals NtbHLH1, a JAF13-like bHLH, interacts with NtMYB6 to enhance proanthocyanidin accumulation in Chinese Narcissus

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Yuxin Fan ◽  
Jiayu Peng ◽  
Jiacheng Wu ◽  
Ping Zhou ◽  
Ruijie He ◽  
...  
Keyword(s):  
Flavonoid Biosynthesis ◽  
Transcriptional Level ◽  
Flavonoid Pathway ◽  
Regulation Of Expression ◽  
Over Expression ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Regulatory Complex ◽  
Positive Regulators ◽  
R2r3 Myb

Abstract Background Flavonoid biosynthesis in plants is primarily regulated at the transcriptional level by transcription factors modulating the expression of genes encoding enzymes in the flavonoid pathway. One of the most studied transcription factor complexes involved in this regulation consists of a MYB, bHLH and WD40. However, in Chinese Narcissus (Narcissus tazetta L. var. chinensis), a popular monocot bulb flower, the regulatory mechanism of flavonoid biosynthesis remains unclear. Results In this work, genes related to the regulatory complex, NtbHLH1 and a R2R3-MYB NtMYB6, were cloned from Chinese Narcissus. Phylogenetic analysis indicated that NtbHLH1 belongs to the JAF13 clade of bHLH IIIf subgroup, while NtMYB6 was highly homologous to positive regulators of proanthocyanidin biosynthesis. Both NtbHLH1 and NtMYB6 have highest expression levels in basal plates of Narcissus, where there is an accumulation of proanthocyanidin. Ectopic over expression of NtbHLH1 in tobacco resulted in an increase in anthocyanin accumulation in flowers, and an up-regulation of expression of the endogenous tobacco bHLH AN1 and flavonoid biosynthesis genes. In contrast, the expression level of LAR gene was significantly increased in NtMYB6-transgenic tobacco. Dual luciferase assays showed that co-infiltration of NtbHLH1 and NtMYB6 significantly activated the promoter of Chinese Narcissus DFR gene. Furthermore, a yeast two-hybrid assay confirmed that NtbHLH1 interacts with NtMYB6. Conclusions Our results suggest that NtbHLH1 may function as a regulatory partner by interacting directly with NtMYB6 to enhance proanthocyanidin accumulation in Chinese Narcissus.

Sign in / Sign up

Export Citation Format

Share Document