Regulation Of Carbon Metabolism Research Articles

Preferential Use of Carbon Sources in Culturable Aerobic Mesophilic Bacteria of Coptotermes curvignathus's (Isoptera: Rhinotermitidae) Gut and Its Foraging Area.

The lower termite, Coptotermes curvignathus, is one of the most prominent plantation pests that feed upon, digest, and receive nourishment from exclusive lignocellulose diets. The objective of this study was to examine the utilization of sole carbon sources by isolated culturable aerobic bacteria among communities from the gut and foraging pathway of C. curvignathus. We study the bacteria occurrence from the gut of C. curvignathus and its surrounding feeding area by comparing the obtained phenotypic fingerprint with Biolog's extensive species library. A total of 24 bacteria have been identified mainly from the family Enterobacteriaceae from the identification of Biolog Gen III. Overall, the bacteria species in the termite gut differ from those of foraging pathway within a location, except Acintobacter baumannii, which was the only bacteria species found in both habitats. Although termites from a different study area do not have the same species of bacteria in the gut, they do have a bacterial community with similar role in degrading certain carbon sources. Sugars were preferential in termite gut isolates, while nitrogen carbon sources were preferential in foraging pathway isolates. The preferential use of specific carbon sources by these two bacterial communities reflects the role of bacteria for regulation of carbon metabolism in the termite gut and foraging pathway.

Diversity of regulatory mechanisms of photosynthetic carbon metabolism in plants and algae.

To clarify the regulatory mechanisms of the Calvin cycle in algae, we analyzed the molecular properties of the enzymes involved in this cycle. We demonstrated that these enzymes were not regulated by redox modulation through the ferredoxin/thioredoxin system under light/dark conditions and were not sensitive to treatments with hydrogen peroxide in vitro, unlike the chloroplastic thiol-modulated enzymes of plants. On the other hand, we found that cyanobacteria possessed a unique enzyme involved in the Calvin cycle. The CP12 protein played an important role in regulating carbon metabolism in the Calvin cycle in cyanobacteria and eukaryotic algae. This review described the regulatory mechanisms of the Calvin cycle in algae and also the effects of alterations to photosynthetic carbon metabolism on plant productivity, carbon partitioning, and the carbon/nitrogen balance using transgenic plants expressing algal genes.

Amino Acid Uptake and Metabolism of Legionella pneumophila Hosted by Acanthamoeba castellanii

Legionella pneumophila survives and replicates within a Legionella-containing vacuole (LCV) of amoebae and macrophages. Less is known about the carbon metabolism of the bacteria within the LCV. We have now analyzed the transfer and usage of amino acids from the natural host organism Acanthamoeba castellanii to Legionella pneumophila under in vivo (LCV) conditions. For this purpose, A. castellanii was 13C-labeled by incubation in buffer containing [U-(13)C(6)]glucose. Subsequently, these 13C-prelabeled amoebae were infected with L. pneumophila wild type or some mutants defective in putative key enzymes or regulators of carbon metabolism. 13C-Isotopologue compositions of amino acids from bacterial and amoebal proteins were then determined by mass spectrometry. In a comparative approach, the profiles documented the efficient uptake of Acanthamoeba amino acids into the LCV and further into L. pneumophila where they served as precursors for bacterial protein biosynthesis. More specifically, A. castellanii synthesized from exogenous [U-13C6]glucose unique isotopologue mixtures of several amino acids including Phe and Tyr, which were also observed in the same amino acids from LCV-grown L. pneumophila. Minor but significant differences were only detected in the isotopologue profiles of Ala, Asp, and Glu from the amoebal or bacterial protein fractions, respectively, indicating partial de novo synthesis of these amino acids by L. pneumophila. The similar isotopologue patterns in amino acids from L. pneumophila wild type and the mutants under study reflected the robustness of amino acid usage in the LCV of A. castellannii.

Functional Proteomic Discovery of Slr0110 as a Central Regulator of Carbohydrate Metabolism in Synechocystis Species PCC6803

The unicellular photosynthetic model-organism cyanobacterium Synechocystis sp. PCC6803 can grow photoautotrophically using CO2 or heterotrophically using glucose as the sole carbon source. Several pathways are involved in carbon metabolism in Synechocystis, and the concerted regulation of these pathways by numerous known and unknown genes is critical for the survival and growth of the organism. Here, we report that a hypothetical protein encoded by the open reading frame slr0110 is necessary for heterotrophic growth of Synechocystis. The slr0110-deletion mutant is defective in glucose uptake, heterotrophic growth, and dark viability without detectable defects in autotrophic growth, whereas the level of photosystem II and the rate of oxygen evolution are increased in the mutant. Quantitative proteomic analysis revealed that several proteins in glycolysis and the oxidative pentose phosphate pathway are down-regulated, whereas proteins in photosystem II and phycobilisome are significantly up-regulated, in the mutant. Among the down-regulated proteins are glucose transporter, glucokinase, glucose-6-phosphate isomerase, and glucose-6-phosphate dehydrogenase and its assembly protein OpcA, suggesting that glycolysis, oxidative pentose phosphate, and glycogen synthesis pathways are significantly inhibited in the mutant, which was further confirmed by enzymatic assays and quantification of glycogen content. These findings establish Slr0110 as a novel central regulator of carbon metabolism in Synechocystis, and shed light on an intricate mechanism whereby photosynthesis and carbon metabolism are well concerted to survive the crisis when one or more pathways of the system are impaired.

SUMOylation regulates the SNF1 protein kinase

The AMP-activated protein kinase (AMPK) is a major stress sensor of mammalian cells. AMPK's homolog in the yeast Saccharomyces cerevisiae, the SNF1 protein kinase, is a central regulator of carbon metabolism that inhibits the Snf3/Rgt2-Rgt1 glucose sensing pathway and activates genes involved in respiration. We present evidence that glucose induces modification of the Snf1 catalytic subunt of SNF1 with the small ubiquitin-like modifier protein SUMO, catalyzed by the SUMO (E3) ligase Mms21. Our results suggest that SUMOylation of Snf1 inhibits its function in two ways: by interaction of SUMO attached to lysine 549 with a SUMO-interacting sequence motif located near the active site of Snf1, and by targeting Snf1 for destruction via the Slx5-Slx8 (SUMO-directed) ubiquitin ligase. These findings reveal another way SNF1 function is regulated in response to carbon source.

Sda1, a Cys2-His2 zinc finger transcription factor, is involved in polyol metabolism and fumonisin B1 production in Fusarium verticillioides.

The ubiquitous ascomycete Fusarium verticillioides causes ear rot and stalk rot of maize, both of which reduce grain quality and yield. Additionally, F. verticillioides produces the mycotoxin fumonisin B1 (FB1) during infection of maize kernels, and thus potentially compromises human and animal health. The current knowledge is fragmentary regarding the regulation of FB1 biosynthesis, particularly when considering interplay with environmental factors such as nutrient availability. In this study, SDA1 of F. verticillioides, predicted to encode a Cys-2 His-2 zinc finger transcription factor, was shown to play a key role in catabolizing select carbon sources. Growth of the SDA1 knock-out mutant (Δsda1) was completely inhibited when sorbitol was the sole carbon source and was severely impaired when exclusively provided mannitol or glycerol. Deletion of SDA1 unexpectedly increased FB1 biosynthesis, but reduced arabitol and mannitol biosynthesis, as compared to the wild-type progenitor. Trichoderma reesei ACE1, a regulator of cellulase and xylanase expression, complemented the F. verticillioides Δsda1 mutant, which indicates that Ace1 and Sda1 are functional orthologs. Taken together, the data indicate that Sda1 is a transcriptional regulator of carbon metabolism and toxin production in F. verticillioides.

Abstract 5239: Unraveling the complex regulatory relationship between PI3K signaling and metabolic transformation in breast cancer.

Abstract Cancer cells exhibit a metabolic phenotype characterized by high rates of glucose uptake and lactate production, known as the Warburg effect. While the Warburg effect and normal proliferative metabolism appear similar, important molecular differences exist. We hypothesize that molecular and metabolic drivers of the Warburg effect can be modulated to impede cancer proliferation without substantial effects on normal tissue growth. Intracellular networks exhibit a variety of emergent non-linear behaviors and, as a result, the use of experimental intuition alone will not be enough to identify these drivers. Using a combination of experimental and theoretical methods, we developed a model of breast cancer progression that includes metabolism and the phosphatidylinositol-3 kinase (PI3K) signaling pathway, an important regulator of carbon metabolism. A key component of our model is a detailed logic network of molecular interactions associated with PI3K signaling as well as regulatory connections to central carbon metabolism, including the ATP/AMP ratio, GLUT receptor activation, hexokinase activation, and changes in the catalytic activity of pyruvate kinase. To validate our model, a series of phospho Western blot analyses were performed using a normal-like breast cell line and a diverse set of breast cancer cell lines exposed to PI3K pathway inhibitors. From these data, a series of predictive network models were constructed representing distinct stages of breast cancer progression. We also generated detailed metabolic flux maps for each cell line using metabolic flux analysis (MFA), a method that relies on carbon-13 tracers, mass-spectrometry, and measurements of extracellular flux to infer intracellular flux. In agreement with recent studies, we found an increase in the reductive carboxylation of glutamine derived alpha-ketoglutarate in cells constitutively adapted to hypoxia. We also identified a potentially important metabolic vulnerability in aggressive breast cancers. Moreover, we found important PI3K network differences at the RNA and protein levels, some of which were isoform specific. Together our data indicate that very different system-level properties are associated with distinct stages of breast cancer progression and metabolic transformation. Our model is suitable for performing in silico molecular perturbations to predict a normal as well as tumor level response to a targeted therapy or combination of therapies. Our approach also serves as a prototype for the use of systems biology methods in personalized medicine where molecular and metabolic data collected from a patient's biopsied tumor is input into a predictive model designed to develop a strategic treatment plan for the patient. The use of predictive models to integrate data from an individual patient will have a profound impact on cancer care decisions and patient outcomes in the future. Citation Format: Michelle L. Wynn, Megan Egbert, Lauren D. Van Wassenhove, Zhi Fen Wu, Firas Midani, Charles Evans, Charles F. Burant, Santiago Schnell, Sofia D. Merajver. Unraveling the complex regulatory relationship between PI3K signaling and metabolic transformation in breast cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5239. doi:10.1158/1538-7445.AM2013-5239

Transcriptional regulation of the ADP-glucose pyrophosphorylase isoforms in the leaf and the stem under long and short photoperiod in lentil

ADP-glucose pyrophosphorylase (AGPase) is a key enzyme in plant starch biosynthesis. It contains large (LS) and small (SS) subunits encoded by two different genes. In this study, we explored the transcriptional regulation of both the LS and SS subunits of AGPase in stem and leaf under different photoperiods length in lentil. To this end, we first isolated and characterized different isoforms of the LS and SS of lentil AGPase and then we performed quantitative real time PCR (qPCR) to see the effect of photoperiod length on the transcription of the AGPase isforms under the different photoperiod regimes in lentil. Analysis of the qPCR results revealed that the transcription of different isoforms of the LSs and the SSs of lentil AGPase are differentially regulated when photoperiod shifted from long-day to short-day in stem and leaves. While transcript levels of LS1 and SS2 in leaf significantly decreased, overall transcript levels of SS1 increased in short-day regime. Our results indicated that day length affects the transcription of lentil AGPase isoforms differentially in stems and leaves most likely to supply carbon from the stem to other tissues to regulate carbon metabolism under short-day conditions.

Shared control of gene expression in bacteria by transcription factors and global physiology of the cell

Gene expression is controlled by the joint effect of (i) the global physiological state of the cell, in particular the activity of the gene expression machinery, and (ii) DNA-binding transcription factors and other specific regulators. We present a model-based approach to distinguish between these two effects using time-resolved measurements of promoter activities. We demonstrate the strength of the approach by analyzing a circuit involved in the regulation of carbon metabolism in E. coli. Our results show that the transcriptional response of the network is controlled by the physiological state of the cell and the signaling metabolite cyclic AMP (cAMP). The absence of a strong regulatory effect of transcription factors suggests that they are not the main coordinators of gene expression changes during growth transitions, but rather that they complement the effect of global physiological control mechanisms. This change of perspective has important consequences for the interpretation of transcriptome data and the design of biological networks in biotechnology and synthetic biology.

Targets of light signalling in Trichoderma reesei

BackgroundThe tropical ascomycete Trichoderma reesei (Hypocrea jecorina) represents one of the most efficient plant cell wall degraders. Regulation of the enzymes required for this process is affected by nutritional signals as well as other environmental signals including light.ResultsOur transcriptome analysis of strains lacking the photoreceptors BLR1 and BLR2 as well as ENV1 revealed a considerable increase in the number of genes showing significantly different transcript levels in light and darkness compared to wild-type. We show that members of all glycoside hydrolase families can be subject to light dependent regulation, hence confirming nutrient utilization including plant cell wall degradation as a major output pathway of light signalling. In contrast to N. crassa, photoreceptor mediated regulation of carbon metabolism in T. reesei occurs primarily by BLR1 and BLR2 via their positive effect on induction of env1 transcription, rather than by a presumed negative effect of ENV1 on the function of the BLR complex. Nevertheless, genes consistently regulated by photoreceptors in N. crassa and T. reesei are significantly enriched in carbon metabolic functions. Hence, different regulatory mechanisms are operative in these two fungi, while the light dependent regulation of plant cell wall degradation appears to be conserved.Analysis of growth on different carbon sources revealed that the oxidoreductive D-galactose and pentose catabolism is influenced by light and ENV1. Transcriptional regulation of the target enzymes in these pathways is enhanced by light and influenced by ENV1, BLR1 and/or BLR2. Additionally we detected an ENV1-regulated genomic cluster of 9 genes including the D-mannitol dehydrogenase gene lxr1, with two genes of this cluster showing consistent regulation in N. crassa.ConclusionsWe show that one major output pathway of light signalling in Trichoderma reesei is regulation of glycoside hydrolase genes and the degradation of hemicellulose building blocks. Targets of ENV1 and BLR1/BLR2 are for the most part distinct and indicate individual functions for ENV1 and the BLR complex besides their postulated regulatory interrelationship.

Gene Regulation of Carbon Fixation, Storage, and Utilization in the DiatomPhaeodactylum tricornutumAcclimated to Light/Dark Cycles

The regulation of carbon metabolism in the diatom Phaeodactylum tricornutum at the cell, metabolite, and gene expression levels in exponential fed-batch cultures is reported. Transcriptional profiles and cell chemistry sampled simultaneously at all time points provide a comprehensive data set on carbon incorporation, fate, and regulation. An increase in Nile Red fluorescence (a proxy for cellular neutral lipids) was observed throughout the light period, and water-soluble glucans increased rapidly in the light period. A near-linear decline in both glucans and lipids was observed during the dark period, and transcription profile data indicated that this decline was associated with the onset of mitosis. More than 4,500 transcripts that were differentially regulated during the light/dark cycle are identified, many of which were associated with carbohydrate and lipid metabolism. Genes not previously described in algae and their regulation in response to light were integrated in this analysis together with proposed roles in metabolic processes. Some very fast light-responding genes in, for example, fatty acid biosynthesis were identified and allocated to biosynthetic processes. Transcripts and cell chemistry data reflect the link between light energy availability and light energy-consuming metabolic processes. Our data confirm the spatial localization of processes in carbon metabolism to either plastids or mitochondria or to glycolysis/gluconeogenesis, which are localized to the cytosol, chloroplast, and mitochondria. Localization and diel expression pattern may be of help to determine the roles of different isoenzymes and the mining of genes involved in light responses and circadian rhythms.

Acetoacetyl-CoA synthetase activity is controlled by a protein acetyltransferase with unique domain organization in Streptomyces lividans.

GCN5-type N-acetyltransferases (GNATs) are enzymes that catalyse the transfer of the acetyl group from acetyl-CoA to a primary amine. GNATs are conserved in all domains of life. Some members of this family of enzymes acetylate the side-chain of specific lysine residues in proteins of diverse function. In bacteria, GNAT-catalysed protein acetylation regulates carbon metabolism, RNA metabolism and transcriptional regulation. Metabolic regulation in Streptomyces species is of interest due to the role of these organisms in natural product synthesis. Here we identify SlPatA, a GNAT in Streptomyces lividans with unique domain organization, and a new acetylation target, namely acetoacetyl-CoA synthetase (SlAacS). The latter has homologues in all domains of life. In vitro and in vivo evidence show that SlAacS is a bona fide acetoacetyl-CoA synthetase. SlPatA acetylates SlAacS more efficiently than it does acetyl-CoA synthetase, an enzyme known to be under acetylation control. SlPatA acetylates SlAacS at the active-site residue Lys617 and acetylation inactivates SlAacS. Acetylated SlAacS was deacetylated by a sirtuin-type protein deacetylase. SlAacS acetylation/deacetylation may represent a conserved mechanism for regulation of acetoacetyl-CoA synthetase activity in all domains of life.

Phosphoproteomic Analysis of Rhodopseudomonas palustris Reveals the Role of Pyruvate Phosphate Dikinase Phosphorylation in Lipid Production

Rhodopseudomonas palustris (R. palustris) is a purple nonsulfur anoxygenic phototrophic bacterium with metabolic versatility and is able to grow under photoheterotrophic and chemoheterotrophic states. It has uses in carbon management, carbon recycling, hydrogen generation, and lipid production; therefore, it has the potential for bioenergy production and biodegradation. This study is the first to identify the phosphoproteome of R. palustris including 100 phosphopeptides from 54 phosphoproteins and 74 phosphopeptides from 42 phosphoproteins in chemoheterotrophic and photoheterotrophic growth conditions, respectively. In the identified phosphoproteome, phosphorylation at the threonine residue, Thr487, of pyruvate phosphate dikinase (PPDK, RPA1051) was found to participate in the regulation of carbon metabolism. Here, we show that PPDK enzyme activity is higher in photoheterotrophic growth, with Thr487 phosphorylation as a possible mediator. Under the same photoheterotrophic conditions, R. palustris with overexpressed wild-type PPDK showed an enhanced accumulation of total lipids than those with mutant PPDK (T487V) form. This study reveals the role of the PPDK in the production of biodiesel material, lipid content, with threonyl-phosphorylation as one of the possible regulatory events during photoheterotrophic growth in R. palustris.

Transcriptome-driven synthetic re-modeling of Escherichia coli to enhance cellobiose utilization

An efficient cellobiose-metabolizing strain of Escherichia coli would provide several industrial benefits, particularly with lignocellulosic biomass substrates. An efficient cellobiose-metabolizing E. coli strain (without the introduction of heterologous genes) was constructed by a combination of promoter engineering of cryptic operons (chb and asc) and adaptive evolution. Gene expression patterns in rapid and slow cellobiose-metabolizing strains were analyzed using DNA microarray. Genes involved in nucleotide biosynthesis, ATP generation, and flagellar assembly were upregulated following adaptation, indicating the possibility of active metabolism and fast growth. On the other hand, genes involved in chemotaxis toward glucose and response to starvation and other stresses were downregulated. No significant changes were observed in the expression of genes regulated by cyclic AMP receptor protein (CRP), the global regulator of carbon metabolism. Overexpression of ascB, which is located in the minor cryptic operon, seems to play a vital role in enhancing cellobiose metabolism. Changes in ascB transcription were confirmed by semiquantitative RT-PCR. The importance of ascB for cell growth on cellobiose was also validated by overexpression and knockout studies. Our study provides new insights into the role of the chb and asc operons in cellobiose metabolism.

Genome-wide location analysis reveals an important overlap between the targets of the yeast transcriptional regulators Rds2 and Adr1

Upon glucose depletion, a massive reprogramming of gene expression occurs in the yeast Saccharomyces cerevisiae for the use of alternate carbon sources such as the nonfermentable compounds ethanol and glycerol. This process is mediated by the master kinase Snf1 that controls the activity of various targets including the transcriptional regulators Cat8, Sip4 and Adr1. We have recently identified Rds2 as an additional player in this pathway. Here, we have performed genome-wide location analysis of Rds2 in cells grown in the presence of glycerol. We show that Rds2 binds to promoters of genes involved in gluconeogenesis, the glyoxylate shunt, and the TCA cycle as well as some genes encoding mitochondrial components or some involved in the stress response. Interestingly, we also detected Rds2 at the promoters of SIP4, ADR1 and HAP4 which encodes the limiting subunit of the Hap2/3/4/5 complex, a regulator of respiration. Strikingly, we observed an important overlap between the targets of Rds2 and Adr1. Finally, we provide a model to account for the complex interplay among these transcriptional regulators.

The β-Subunit of the SnRK1 Complex Is Phosphorylated by the Plant Cell Death Suppressor Adi3

The protein kinase AvrPto-dependent Pto-interacting protein3 (Adi3) is a known suppressor of cell death, and loss of its function has been correlated with cell death induction during the tomato (Solanum lycopersicum) resistance response to its pathogen Pseudomonas syringae pv tomato. However, Adi3 downstream interactors that may play a role in cell death regulation have not been identified. We used a yeast two-hybrid screen to identify the plant SnRK1 (for Sucrose non-Fermenting-1-Related Protein Kinase1) protein as an Adi3-interacting protein. SnRK1 functions as a regulator of carbon metabolism and responses to biotic and abiotic stresses. SnRK1 exists in a heterotrimeric complex with a catalytic α-subunit (SnRK1), a substrate-interacting β-subunit, and a regulatory γ-subunit. Here, we show that Adi3 interacts with, but does not phosphorylate, the SnRK1 α-subunit. The ability of Adi3 to phosphorylate the four identified tomato β-subunits was also examined, and it was found that only the Galactose Metabolism83 (Gal83) β-subunit was phosphorylated by Adi3. This phosphorylation site on Gal83 was identified as serine-26 using a mutational approach and mass spectrometry. In vivo expression of Gal83 indicates that it contains multiple phosphorylation sites, one of which is serine-26. An active SnRK1 complex containing Gal83 as the β-subunit and sucrose nonfermenting4 as the γ-subunit was constructed to examine functional aspects of the Adi3 interaction with SnRK1 and Gal83. These assays revealed that Adi3 is capable of suppressing the kinase activity of the SnRK1 complex through Gal83 phosphorylation plus the interaction with SnRK1 and suggested that this function may be related to the cell death suppression activity of Adi3.

Principles of carbon catabolite repression in the rice blast fungus: Tps1, Nmr1-3, and a MATE-family pump regulate glucose metabolism during infection.

Understanding the genetic pathways that regulate how pathogenic fungi respond to their environment is paramount to developing effective mitigation strategies against disease. Carbon catabolite repression (CCR) is a global regulatory mechanism found in a wide range of microbial organisms that ensures the preferential utilization of glucose over less favourable carbon sources, but little is known about the components of CCR in filamentous fungi. Here we report three new mediators of CCR in the devastating rice blast fungus Magnaporthe oryzae: the sugar sensor Tps1, the Nmr1-3 inhibitor proteins, and the multidrug and toxin extrusion (MATE)–family pump, Mdt1. Using simple plate tests coupled with transcriptional analysis, we show that Tps1, in response to glucose-6-phosphate sensing, triggers CCR via the inactivation of Nmr1-3. In addition, by dissecting the CCR pathway using Agrobacterium tumefaciens-mediated mutagenesis, we also show that Mdt1 is an additional and previously unknown regulator of glucose metabolism. Mdt1 regulates glucose assimilation downstream of Tps1 and is necessary for nutrient utilization, sporulation, and pathogenicity. This is the first functional characterization of a MATE–family protein in filamentous fungi and the first description of a MATE protein in genetic regulation or plant pathogenicity. Perturbing CCR in Δtps1 and MDT1 disruption strains thus results in physiological defects that impact pathogenesis, possibly through the early expression of cell wall–degrading enzymes. Taken together, the importance of discovering three new regulators of carbon metabolism lies in understanding how M. oryzae and other pathogenic fungi respond to nutrient availability and control development during infection.

Heterologous expression of human phosphodiesterase 3A (hPDE3A) improves ethanol production in Saccharomyces cerevisiae

Growing demands for energy and limitation of fossil fuels have promoted research on biofuels, in particular, on bioethanol. S. cerevisiae may be a very economical system to achieve higher ethanol concentrations. For that, the improvement of yield and efficiency of ethanol production is necessary, which is influenced by various factors. cAMP, a primary cell cycle regulator, plays a pivotal role in the regulation of carbon metabolism, cell growth, cell size, cell cycle, and stress responses. Phosphodiesterases (PDEs) degrade cAMP. In order to provide the basis for improved ethanol production in yeast, we attempted to determine if regulation of cell cycle is related to the control of ethanol production. We heterologously expressed several isoforms of human PDE3A (full‐length and several truncated variants) in yeast and confirmed their catalytic activities. All truncated variants decreased cell growth rate, whereas full‐length hPDE3A accelerated it and increased ethanol yield. Although the cell size decreased in cells expressing full‐length hPDE3A, total dry cell mass was greatly increased. These indicate that PDE3A, which regulates cell cycle progression in oocytes and cultured vascular smooth muscle cells, accelerates cell growth rate in yeast, which results in increased biomass accompanied by higher ethanol production. Research support provided by NHLBI.

Snf1/AMPK regulates Gcn5 occupancy, H3 acetylation and chromatin remodelling at S. cerevisiae ADY2 promoter

The ability of cells to respond to changes in their environment is mediated by transcription factors that remodel chromatin and reprogram expression of specific subsets of genes. In Saccharomyces cerevisiae, changes in carbon source lead to gene induction by Adr1 and Cat8 that are known to require the upstream function of the Snf1 protein kinase, the central regulator of carbon metabolism, to exert their activating effect. How Snf1 facilitates transcription activation by Adr1 and Cat8 is not known. Here we show that under derepressing conditions, deletion of SNF1 abolishes the increase of histone H3 acetylation at the promoter of the glucose-repressed ADY2 gene, and as a consequence profoundly affects the chromatin structural alterations accompanying transcriptional activation. Adr1 and Cat8 are not required to regulate the acetylation switch and show only a partial influence on chromatin remodelling at this promoter, though their double deletion completely abolishes mRNA accumulation. Finally, we show that under derepressing conditions the recruitment of the histone acetyltransferase Gcn5 is abolished by SNF1 deletion, possibly explaining the lack of increased histone H3 acetylation and nucleosome remodelling.The results highlight a mechanism by which signalling to chromatin provides an essential permissive signal that is required for activation by glucose-responsive transcription factors.

A dual‐targeted purple acid phosphatase in Arabidopsis thaliana moderates carbon metabolism and its overexpression leads to faster plant growth and higher seed yield

• Overexpression of AtPAP2, a purple acid phosphatase (PAP) with a unique C-terminal hydrophobic motif in Arabidopsis, resulted in earlier bolting and a higher seed yield. Metabolite analysis showed that the shoots of AtPAP2 overexpression lines contained higher levels of sugars and tricarboxylic acid (TCA) metabolites. Enzyme assays showed that sucrose phosphate synthase (SPS) activity was significantly upregulated in the overexpression lines. The higher SPS activity arose from a higher level of SPS protein, and was independent of SnRK1. • AtPAP2 was found to be targeted to both plastids and mitochondria via its C-terminal hydrophobic motif. Ectopic expression of a truncated AtPAP2 without this C-terminal motif in Arabidopsis indicated that the subcellular localization of AtPAP2 is essential for its biological actions. • Plant PAPs are generally considered to mediate phosphorus acquisition and redistribution. AtPAP2 is the first PAP shown to modulate carbon metabolism and the first shown to be dual-targeted to both plastids and mitochondria by a C-terminal targeting signal. • One PAP-like sequence carrying a hydrophobic C-terminal motif could be identified in the genome of the smallest free-living photosynthetic eukaryote, Ostreococcus tauri. This might reflect a common ancestral function of AtPAP2-like sequences in the regulation of carbon metabolism.