Compartmentation of terpenoid biosynthesis in green plants. A proposed route of acetyl-coenzyme A synthesis in maize chloroplasts.
Ontology highlight
ABSTRACT:
SUBMITTER: Shah SP
PROVIDER: S-EPMC1184867 | biostudies-other | 1969 Sep
REPOSITORIES: biostudies-other
Similar Datasets
Project description:Preparations of acetyl-CoA carboxylase [acetyl-CoA-carbon-dioxide ligase (ADP-forming), EC 6.4.1.2] have been obtained from the plastids of avocado (Persea americana) fruit mesocarp and from spinach (Spinacia oleracea) chloroplasts. Both preparations required bovine serum albumin, HCO3-, citrate and glycerol for stabilization. The molecular weight of the avocado enzyme was about 6.5 X 10(5) on the basis of 1 mol of biotin/mol of enzyme, the behaviour of both enzymes on gel filtration being in accord with such a value. Removal of the stabilizing bovine serum albumin resulted in the loss of a biotin-containing fragment from the avocado enzyme. Citrate stabilized the enzyme at 10 mM and activated it optimally at 3.0 mM, effecting an approx. 2-fold increase in Vmax. It is suggested that in vivo the enzyme may be located within the chloroplast lamellae.
| S-EPMC1162450 | biostudies-other
Project description:A partially dominant mutation exhibiting increased tolerance to cyclohexanedione and aryloxyphenoxypropionate herbicides was isolated by exposing susceptible maize (Zea mays) tissue cultures to increasingly inhibitory concentrations of sethoxydim (a cyclohexanedione). The selected tissue culture (S2) was greater than 40-fold more tolerant to sethoxydim and 20-fold more tolerant to haloxyfop (an aryloxyphenoxypropionate) than the nonselected wild-type tissue culture. Regenerated S2 plants were heterozygous for the mutant allele and exhibited a high-level, but not complete, tolerance to both herbicides. Homozygous mutant families derived by self-pollinating the regenerated S2 plants exhibited no injury after treatment with 0.8 kg of sethoxydim per ha, which was greater than 16-fold the rate lethal to wild-type plants. Acetyl-coenzyme A carboxylase (ACCase; EC 6.4.1.2) is the target enzyme of cyclohexanedione and aryloxyphenoxypropionate herbicides. ACCase activities of the nonselected wild-type and homozygous mutant seedlings were similar in the absence of herbicide. ACCase activity from homozygous tolerant plants required greater than 100-fold more sethoxydim and 16-fold more haloxyfop for 50% inhibition than ACCase from wild-type plants. These results indicate that tolerance to sethoxydim and haloxyfop is controlled by a partially dominant nuclear mutation encoding a herbicide-insensitive alteration in maize ACCase.
| S-EPMC54706 | biostudies-literature
Project description:Most terpenoids are derived from the basic terpene skeletons of geranyl pyrophosphate (GPP, C10), farnesyl-PP (FPP, C15) and geranylgeranyl-PP (GGPP, C20). The trans-prenyltransferases (PTs) mediate the sequential head-to-tail condensation of an isopentenyl-PP (C5) with allylic substrates. The in silico structural comparative analyses of rice trans-PTs with 136 plant trans-PT genes allowed twelve rice PTs to be identified as GGPS_LSU (OsGGPS1), homomeric G(G)PS (OsGPS) and GGPS_SSU-II (OsGRP) in Group I; two solanesyl-PP synthase (OsSPS2 and 3) and two polyprenyl-PP synthases (OsSPS1 and 4) in Group II; and five FPSs (OsFPS1, 2, 3, 4 and 5) in Group III. Additionally, several residues in "three floors" for the chain length and several essential domains for enzymatic activities specifically varied in rice, potentiating evolutionarily rice-specific biochemical functions of twelve trans-PTs. Moreover, expression profiling and localization patterns revealed their functional compartmentation in rice. Taken together, we propose the predicted topology-based working model of rice PTs with corresponding terpene metabolites: GPP/GGPPs mainly in plastoglobuli, SPPs in stroma, PPPs in cytosol, mitochondria and chloroplast and FPPs in cytosol. Our findings could be suitably applied to metabolic engineering for producing functional terpene metabolites in rice systems.
| S-EPMC7728057 | biostudies-literature
Project description:In contrast to the cyanobacterial ancestor, chloroplast gene expression is predominantly governed on the post-transcriptional level such as modifications of the RNA sequence, decay rates, exo- and endonucleolytic processing as well as translational events. The concerted function of numerous chloroplast RNA-binding proteins plays a fundamental and often essential role in all these processes but our understanding of their impact in regulation of RNA degradation is only at the beginning. Moreover, metabolic processes and post-translational modifications are thought to affect the function of RNA protectors. These protectors contain a variety of different RNA-recognition motifs, which often appear as multiple repeats. They are required for normal plant growth and development as well as diverse stress responses and acclimation processes. Interestingly, most of the protectors are plant specific which reflects a fast-evolving RNA metabolism in chloroplasts congruent with the diverging RNA targets. Here, we mainly focused on the characteristics of known chloroplast RNA-binding proteins that protect exonuclease-sensitive sites in chloroplasts of vascular plants.
| S-EPMC5897788 | biostudies-literature
Project description:A simple off-column capillary electrophoretic (CE) assay for measuring acetyl coenzyme A carboxylase holoenzyme (holo-ACC) activity and inhibition was developed. The two reactions catalyzed by the holo-ACC components, biotin carboxylase (BC) and carboxyltransferase (CT), were simultaneously monitored in this assay. Acetyl coenzyme A (CoA), malonyl-CoA, adenosine triphosphate (ATP), and adenosine diphosphate (ADP) were separated by capillary electrophoresis, and the depletion of ATP and acetyl-CoA as well as the production of ADP and malonyl-CoA were monitored. Inhibition of holo-ACC by the BC inhibitor, 2-amino-N,N-dibenzyloxazole-5-carboxamide, and the carboxyltransferase inhibitor, andrimid, was confirmed using this assay. A previously reported off-column CE assay for only the CT component of ACC was optimized, and an off-column CE assay for the BC component of ACC also was developed.
| S-EPMC3627828 | biostudies-literature
Project description:Cells of Escherichia coli growing on sugars that result in catabolite repression or amino acids that feed into glycolysis undergo a metabolic switch associated with the production and utilization of acetate. As they divide exponentially, these cells excrete acetate via the phosphotransacetylase-acetate kinase pathway. As they begin the transition to stationary phase, they instead resorb acetate, activate it to acetyl coenzyme A (acetyl-CoA) by means of the enzyme acetyl-CoA synthetase (Acs) and utilize it to generate energy and biosynthetic components via the tricarboxylic acid cycle and the glyoxylate shunt, respectively. Here, we present evidence that this switch occurs primarily through the induction of acs and that the timing and magnitude of this induction depend, in part, on the direct action of the carbon regulator cyclic AMP receptor protein (CRP) and the oxygen regulator FNR. It also depends, probably indirectly, upon the glyoxylate shunt repressor IclR, its activator FadR, and many enzymes involved in acetate metabolism. On the basis of these results, we propose that cells induce acs, and thus their ability to assimilate acetate, in response to rising cyclic AMP levels, falling oxygen partial pressure, and the flux of carbon through acetate-associated pathways.
| S-EPMC101899 | biostudies-literature
Project description:Compared with the ancestral C3 state, C4 photosynthesis occurs at higher rates with improved water and nitrogen use efficiencies. In both C3 and C4 plants, rates of photosynthesis increase with light intensity and are maximal around midday. We determined that in the absence of light or temperature fluctuations, photosynthesis in maize (Zea mays) peaks in the middle of the subjective photoperiod. To investigate the molecular processes associated with these temporal changes, we performed RNA sequencing of maize mesophyll and bundle sheath strands over a 24-h time course. Preferential expression of C4 cycle genes in these cell types was strongest between 6 and 10 h after dawn when rates of photosynthesis were highest. For the bundle sheath, DNA motif enrichment and gene coexpression analyses suggested members of the DNA binding with one finger (DOF) and MADS (MINICHROMOSOME MAINTENANCE FACTOR 1/AGAMOUS/DEFICIENS/Serum Response Factor)-domain transcription factor families mediate diurnal fluctuations in C4 gene expression, while trans-activation assays in planta confirmed their ability to activate promoter fragments from bundle sheath expressed genes. The work thus identifies transcriptional regulators and peaks in cell-specific C4 gene expression coincident with maximum rates of photosynthesis in the maize leaf at midday.
| S-EPMC10663113 | biostudies-literature
Project description:We investigated the organization of photosystem II (PSII) in agranal bundle sheath thylakoids from a C(4) plant maize. Using blue native/SDS-PAGE and single particle analysis, we show for the first time that PSII in the bundle sheath (BS) chloroplasts exists in a dimeric form and forms light-harvesting complex II (LHCII).PSII supercomplexes. We also demonstrate that a similar set of photosynthetic membrane complexes exists in mesophyll and agranal BS chloroplasts, including intact LHCI.PSI supercomplexes, PSI monomers, PSII core dimers, PSII monomers devoid of CP43, LHCII trimers, LHCII monomers, ATP synthase, and cytochrome b(6)f complex. Fluorescence functional measurements clearly indicate that BS chloroplasts contain PSII complexes that are capable of performing charge separation and are efficiently sensitized by the associated LHCII. We identified a fraction of LHCII present within BS thylakoids that is weakly energetically coupled to the PSII reaction center; however, the majority of BS LHCII is shown to be tightly connected to PSII. Overall, we demonstrate that organization of the photosynthetic apparatus in BS agranal chloroplasts of a model C(4) plant is clearly distinct from that of the stroma lamellae of the C(3) plants. In particular, supramolecular organization of the dimeric LHCII.PSII in the BS thylakoids strongly suggests that PSII in the BS agranal membranes may donate electrons to PSI. We propose that the residual PSII activity may supply electrons to poise cyclic electron flow around PSI and prevent PSI overoxidation, which is essential for the CO(2) fixation in BS cells, and hence, may optimize ATP production within this compartment.
| S-EPMC3258860 | biostudies-literature
Project description:The mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) is a master regulator of cell growth and metabolism. Leucine (Leu) activates mTORC1 and many have tried to identify the mechanisms whereby cells sense Leu in this context. Here we describe that the Leu metabolite acetyl-coenzyme A (AcCoA) positively regulates mTORC1 activity by EP300-mediated acetylation of the mTORC1 regulator, Raptor, at K1097. Leu metabolism and consequent mTORC1 activity are regulated by intermediary enzymes. As AcCoA is a Leu metabolite, this process directly correlates with Leu abundance, and does not require Leu sensing via intermediary proteins, as has been described previously. Importantly, we describe that this pathway regulates mTORC1 in a cell-type-specific manner. Finally, we observed decreased acetylated Raptor, and inhibited mTORC1 and EP300 activity in fasted mice tissues. These results provide a direct mechanism for mTORC1 regulation by Leu metabolism.
| S-EPMC6331339 | biostudies-literature
Project description:affy_ccr_maize - affy_ccr_maize - Cinnamoyl-CoA reductase (CCR) catalyzes a key step in monolignol biosynthesis. We show that downregulation of CCR in maize was associated with lower lignin content and a strong decrease in H units. Concomitantly, these cell wall modifications were associated with higher digestibility. On another hand, immunocytochemistry indicated a modification of lignification pattern and cellulose content. Transcript profiling was used as comprehensive phenotyping tools to investigate how CCR downregulation impacted metabolism and the biosynthesis of other cell wall polymers. -2 wild type and 2 CCR mutants were compared. Plants were grown in greenhouse condition and harvested at 7-8 leaf stages. Keywords: gene knock in (transgenic)
2009-07-22 | GSE11531 | GEO