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  1 / 580 MEDLINE  
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PMID:28465173
Autor:Xue J; Balamurugan S; Li DW; Liu YH; Zeng H; Wang L; Yang WD; Liu JS; Li HY
Endereço:Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institutes, College of Life Science and Technology, Jinan University, Guangzhou 510632, China.
Título:Glucose-6-phosphate dehydrogenase as a target for highly efficient fatty acid biosynthesis in microalgae by enhancing NADPH supply.
Fonte:Metab Eng; 41:212-221, 2017 05.
ISSN:1096-7184
País de publicação:Belgium
Idioma:eng
Resumo:Oleaginous microalgae have great prospects in the fields of feed, nutrition, biofuel, etc. However, biomass and lipid productivity in microalgae remain a major economic and technological bottleneck. Here we present a novel regulatory target, glucose-6-phosphate dehydrogenase (G6PD) from the pentose phosphate pathway (PPP), in boosting microalgal lipid accumulation. G6PD, involved in the formation of NADPH demanded in fatty acid biosynthesis as reducing power, was characterized in oleaginous microalga Phaeodactylum tricornutum. In G6PD overexpressing microalgae, transcript abundance of G6PD increased by 4.4-fold, and G6PD enzyme activity increased by more than 3.1-fold with enhanced NADPH production. Consequently, the lipid content increased by 2.7-fold and reached up to 55.7% of dry weight, while cell growth was not apparently affected. The fatty acid composition exhibited significant changes, including a remarkable increase in monounsaturated fatty acids C16:1 and C18:1 concomitant with a decrease in polyunsaturated fatty acids C20:5 and C22:6. G6PD was localized to the chloroplast and its overexpression stimulated an increase in the number and size of oil bodies. Proteomic and metabolomic analyzes revealed that G6PD play a key role in regulating pentose phosphate pathway and subsequently upregulating NADPH consuming pathways such as fatty acid synthesis, thus eventually leading to lipid accumulation. Our findings show the critical role of G6PD in microalgal lipid accumulation by enhancing NADPH supply and demonstrate that G6PD is a promising target for metabolic engineering.
Tipo de publicação: JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
Nome de substância:0 (Chloroplast Proteins); 0 (Fatty Acids, Unsaturated); 53-59-8 (NADP); 56-73-5 (Glucose-6-Phosphate); EC 1.1.1.49 (Glucosephosphate Dehydrogenase)


  2 / 580 MEDLINE  
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PMID:28985404
Autor:Cavaiuolo M; Kuras R; Wollman FA; Choquet Y; Vallon O
Endereço:Unité Mixte de Recherche 7141, CNRS/UPMC, Institut de Biologie Physico-Chimique, F-75005 Paris, France.
Título:Small RNA profiling in Chlamydomonas: insights into chloroplast RNA metabolism.
Fonte:Nucleic Acids Res; 45(18):10783-10799, 2017 Oct 13.
ISSN:1362-4962
País de publicação:England
Idioma:eng
Resumo:In Chlamydomonas reinhardtii, regulation of chloroplast gene expression is mainly post-transcriptional. It requires nucleus-encoded trans-acting protein factors for maturation/stabilization (M factors) or translation (T factors) of specific target mRNAs. We used long- and small-RNA sequencing to generate a detailed map of the transcriptome. Clusters of sRNAs marked the 5' end of all mature mRNAs. Their absence in M-factor mutants reflects the protection of transcript 5' end by the cognate factor. Enzymatic removal of 5'-triphosphates allowed identifying those cosRNA that mark a transcription start site. We detected another class of sRNAs derived from low abundance transcripts, antisense to mRNAs. The formation of antisense sRNAs required the presence of the complementary mRNA and was stimulated when translation was inhibited by chloramphenicol or lincomycin. We propose that they derive from degradation of double-stranded RNAs generated by pairing of antisense and sense transcripts, a process normally hindered by the traveling of the ribosomes. In addition, chloramphenicol treatment, by freezing ribosomes on the mRNA, caused the accumulation of 32-34 nt ribosome-protected fragments. Using this 'in vivo ribosome footprinting', we identified the function and molecular target of two candidate trans-acting factors.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Chloroplast Proteins); 0 (Nucleic Acid Synthesis Inhibitors); 0 (Plant Proteins); 0 (RNA, Antisense); 0 (RNA, Chloroplast); 0 (RNA, Messenger); 0 (RNA, Ribosomal); 0 (RNA, Small Untranslated); 9014-25-9 (RNA, Transfer)


  3 / 580 MEDLINE  
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PMID:28977480
Autor:Peralta-Castro A; Baruch-Torres N; Brieba LG
Endereço:Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados del IPN, Apartado Postal 629, Irapuato, Guanajuato, CP 36821, México.
Título:Plant organellar DNA primase-helicase synthesizes RNA primers for organellar DNA polymerases using a unique recognition sequence.
Fonte:Nucleic Acids Res; 45(18):10764-10774, 2017 Oct 13.
ISSN:1362-4962
País de publicação:England
Idioma:eng
Resumo:DNA primases recognize single-stranded DNA (ssDNA) sequences to synthesize RNA primers during lagging-strand replication. Arabidopsis thaliana encodes an ortholog of the DNA primase-helicase from bacteriophage T7, dubbed AtTwinkle, that localizes in chloroplasts and mitochondria. Herein, we report that AtTwinkle synthesizes RNA primers from a 5'-(G/C)GGA-3' template sequence. Within this sequence, the underlined nucleotides are cryptic, meaning that they are essential for template recognition but are not instructional during RNA synthesis. Thus, in contrast to all primases characterized to date, the sequence recognized by AtTwinkle requires two nucleotides (5'-GA-3') as a cryptic element. The divergent zinc finger binding domain (ZBD) of the primase module of AtTwinkle may be responsible for template sequence recognition. During oligoribonucleotide synthesis, AtTwinkle shows a strong preference for rCTP as its initial ribonucleotide and a moderate preference for rGMP or rCMP incorporation during elongation. RNA products synthetized by AtTwinkle are efficiently used as primers for plant organellar DNA polymerases. In sum, our data strongly suggest that AtTwinkle primes organellar DNA polymerases during lagging strand synthesis in plant mitochondria and chloroplast following a primase-mediated mechanism. This mechanism contrasts to lagging-strand DNA replication in metazoan mitochondria, in which transcripts synthesized by mitochondrial RNA polymerase prime mitochondrial DNA polymerase γ.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Arabidopsis Proteins); 0 (Chloroplast Proteins); 0 (DNA, Single-Stranded); 0 (Mitochondrial Proteins); 0 (Multifunctional Enzymes); 0 (RNA primers); 0 (Ribonucleotides); 0 (Twinkle protein, Arabidopsis); 63231-63-0 (RNA); EC 2.7.7.- (DNA Primase); EC 2.7.7.7 (DNA-Directed DNA Polymerase); EC 3.6.4.- (DNA Helicases)


  4 / 580 MEDLINE  
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PMID:28887777
Autor:Lehniger MK; Finster S; Melonek J; Oetke S; Krupinska K; Schmitz-Linneweber C
Endereço:Institute of Biology, Humboldt University of Berlin, Philippstr. 11-13, 10115, Berlin, Germany.
Título:Global RNA association with the transcriptionally active chromosome of chloroplasts.
Fonte:Plant Mol Biol; 95(3):303-311, 2017 Oct.
ISSN:1573-5028
País de publicação:Netherlands
Idioma:eng
Resumo:KEY MESSAGE: Processed chloroplast RNAs are co-enriched with preparations of the chloroplast transcriptionally active chromosome. Chloroplast genomes are organized as a polyploid DNA-protein structure called the nucleoid. Transcriptionally active chloroplast DNA together with tightly bound protein factors can be purified by gel filtration as a functional entity called the transcriptionally active chromosome (TAC). Previous proteomics analyses of nucleoids and of TACs demonstrated a considerable overlap in protein composition including RNA binding proteins. Therefore the RNA content of TAC preparations from Nicotiana tabacum was determined using whole genome tiling arrays. A large number of chloroplast RNAs was found to be associated with the TAC. The pattern of RNAs attached to the TAC consists of RNAs produced by different chloroplast RNA polymerases and differs from the pattern of RNA found in input controls. An analysis of RNA splicing and RNA editing of selected RNA species demonstrated that TAC-associated RNAs are processed to a similar extent as the RNA in input controls. Thus, TAC fractions contain a specific subset of the processed chloroplast transcriptome.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Chloroplast Proteins); 0 (DNA, Chloroplast); 0 (RNA, Plant); 0 (Ribonucleoproteins)


  5 / 580 MEDLINE  
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PMID:28630009
Autor:Buchensky C; Sánchez M; Carrillo M; Palacios O; Capdevila M; Domínguez-Vera JM; Busi MV; Atrian S; Pagani MA; Gomez-Casati DF
Endereço:CEFOBI - CONICET, Centro de Estudios Fotosintéticos y Bioquímicos - Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Santa Fe, Argentina.
Título:Identification of two frataxin isoforms in Zea mays: Structural and functional studies.
Fonte:Biochimie; 140:34-47, 2017 Sep.
ISSN:1638-6183
País de publicação:France
Idioma:eng
Resumo:Frataxin is a ubiquitous protein that plays a role in Fe-S cluster biosynthesis and iron and heme metabolism, although its molecular functions are not entirely clear. In non-photosynthetic eukaryotes, frataxin is encoded by a single gene, and the protein localizes to mitochondria. Here we report the presence of two functional frataxin isoforms in Zea mays, ZmFH-1 and ZmFH-2. We confirmed our previous findings regarding plant frataxins: both proteins have dual localization in mitochondria and chloroplasts. Physiological, biochemical and biophysical studies show some differences in the expression pattern, protection against oxidants and in the aggregation state of both isoforms, suggesting that the two frataxin homologs would play similar but not identical roles in plant cell metabolism. In addition, two specific features of plant frataxins were evidenced: their ability to form dimers and their tendency to undergo conformational change under oxygen exposure.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Chloroplast Proteins); 0 (Iron-Binding Proteins); 0 (Mitochondrial Proteins); 0 (Protein Isoforms); 0 (frataxin)


  6 / 580 MEDLINE  
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PMID:28582576
Autor:Ahmed T; Shi J; Bhushan S
Endereço:School of Biological Sciences, Nanyang Technological University, 637551, Singapore.
Título:Unique localization of the plastid-specific ribosomal proteins in the chloroplast ribosome small subunit provides mechanistic insights into the chloroplastic translation.
Fonte:Nucleic Acids Res; 45(14):8581-8595, 2017 Aug 21.
ISSN:1362-4962
País de publicação:England
Idioma:eng
Resumo:Chloroplastic translation is mediated by a bacterial-type 70S chloroplast ribosome. During the evolution, chloroplast ribosomes have acquired five plastid-specific ribosomal proteins or PSRPs (cS22, cS23, bTHXc, cL37 and cL38) which have been suggested to play important regulatory roles in translation. However, their exact locations on the chloroplast ribosome remain elusive due to lack of a high-resolution structure, hindering our progress to understand their possible roles. Here we present a cryo-EM structure of the 70S chloroplast ribosome from spinach resolved to 3.4 Å and focus our discussion mainly on the architecture of the 30S small subunit (SSU) which is resolved to 3.7 Å. cS22 localizes at the SSU foot where it seems to compensate for the deletions in 16S rRNA. The mRNA exit site is highly remodeled due to the presence of cS23 suggesting an alternative mode of translation initiation. bTHXc is positioned at the SSU head and appears to stabilize the intersubunit bridge B1b during thermal fluctuations. The translation factor plastid pY binds to the SSU on the intersubunit side and interacts with the conserved nucleotide bases involved in decoding. Most of the intersubunit bridges are conserved compared to the bacteria, except for a new bridge involving uL2c and bS6c.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Chloroplast Proteins); 0 (RNA, Messenger); 0 (Ribosomal Proteins)


  7 / 580 MEDLINE  
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PMID:28429322
Autor:Schwartzbach SD
Endereço:Department of Biological Sciences, University of Memphis, Memphis, TN, 38152, USA. sdschwrt@memphis.edu.
Título:Photo and Nutritional Regulation of Euglena Organelle Development.
Fonte:Adv Exp Med Biol; 979:159-182, 2017.
ISSN:0065-2598
País de publicação:United States
Idioma:eng
Resumo:Euglena can use light and CO , photosynthesis, as well as a large variety of organic molecules as the sole source of carbon and energy for growth. Light induces the enzymes, in this case an entire organelle, the chloroplast, that is required to use CO as the sole source of carbon and energy for growth. Ethanol, but not malate, inhibits the photoinduction of chloroplast enzymes and induces the synthesis of the glyoxylate cycle enzymes that comprise the unique metabolic pathway leading to two carbon, ethanol and acetate, assimilation. In resting, carbon starved cells, light mobilizes the degradation of the storage carbohydrate paramylum and transiently induces the mitochondrial proteins required for the aerobic metabolism of paramylum to provide the carbon and energy required for chloroplast development. Other mitochondrial proteins are degraded upon light exposure providing the amino acids required for the synthesis of light induced proteins. Changes in protein levels are due to increased and decreased rates of synthesis rather than changes in degradation rates. Changes in protein synthesis rates occur in the absence of a concomitant increase in the levels of mRNAs encoding these proteins indicative of photo and metabolic control at the translational rather than the transcriptional level. The fraction of mRNA encoding a light induced protein such as the light harvesting chlorophyll a/b binding protein of photosystem II, (LHCPII) associated with polysomes in the dark is similar to the fraction associated with polysomes in the light indicative of photoregulation at the level of translational elongation. Ethanol, a carbon source whose assimilation requires carbon source specific enzymes, the glyoxylate cycle enzymes, represses the synthesis of chloroplast enzymes uniquely required to use light and CO as the sole source of carbon and energy for growth. The catabolite sensitivity of chloroplast development provides a mechanism to prioritize carbon source utilization. Euglena uses all of its resources to develop the metabolic capacity to utilize carbon sources such as ethanol which are rarely in the environment and delays until the rare carbon source is no longer available forming the chloroplast which is required to utilize the ubiquitous carbon source, light and CO .
Tipo de publicação: JOURNAL ARTICLE; REVIEW
Nome de substância:0 (Chloroplast Proteins); 0 (Mitochondrial Proteins); 0 (Protozoan Proteins)


  8 / 580 MEDLINE  
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PMID:28422996
Autor:Guan X; Li Z; Zhang Z; Wei X; Xie J; Chen J; Chen Q
Endereço:College of Horticulture, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China.
Título:Overexpression of an EaZIP gene devoid of transit peptide sequence induced leaf variegation in tobacco.
Fonte:PLoS One; 12(4):e0175995, 2017.
ISSN:1932-6203
País de publicação:United States
Idioma:eng
Resumo:Leaf variegation is an ornamental trait that is not only biologically but also economically important. In our previous study, a Mg-protoporphyrin IX monomethyl ester cyclase homologue, EaZIP (Epipremnum aureum leucine zipper) was found to be associated with leaf variegation in Epipremnum aureum (Linden & Andre) G.S. Bunting. The protein product of this nuclear-encoded gene is targeted back to chloroplast involving in chlorophyll biosynthesis. Based on a web-based homology analysis, the EaZIP was found to lack a chloroplast transit peptide (cTP) sequence. In the present study, we tested if overexpression of the EaZIP cDNA with or without the cTP sequence could affect leaf variegation. Transgenic tobacco plants overexpressing EaZIP genes with (EaZIPwcTP) and without (EaZIPwocTP) cTP sequence were generated. Many plant lines harboring EaZIPwocTP showed variegated leaves, while none of the plant lines with EaZIPwcTP produced such a phenotype. Molecular analysis of T0 plants and selfed T1 progeny, as well as observations of tagged marker GFP (green fluorescent protein) did not show any other difference in patterns of gene integrity and expression. Results from this study indicate that transgenic approach for expressing EaZIPwocTP could be a novel method of generating variegated plants even through the underlying mechanisms remain to be elucidated.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Chloroplast Proteins); 0 (DNA, Complementary); 0 (Plant Proteins); 0 (Protein Sorting Signals); 0 (Transcription Factors); 0 (chloroplast transit peptides)


  9 / 580 MEDLINE  
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PMID:28407006
Autor:Cuesta-Seijo JA; Ruzanski C; Krucewicz K; Meier S; Hägglund P; Svensson B; Palcic MM
Endereço:Carlsberg Research Laboratory, J.C. Jacobsens Gade 4, DK-1799 Copenhagen V, Denmark.
Título:Functional and structural characterization of plastidic starch phosphorylase during barley endosperm development.
Fonte:PLoS One; 12(4):e0175488, 2017.
ISSN:1932-6203
País de publicação:United States
Idioma:eng
Resumo:The production of starch is essential for human nutrition and represents a major metabolic flux in the biosphere. The biosynthesis of starch in storage organs like barley endosperm operates via two main pathways using different substrates: starch synthases use ADP-glucose to produce amylose and amylopectin, the two major components of starch, whereas starch phosphorylase (Pho1) uses glucose-1-phosphate (G1P), a precursor for ADP-glucose production, to produce α-1,4 glucans. The significance of the Pho1 pathway in starch biosynthesis has remained unclear. To elucidate the importance of barley Pho1 (HvPho1) for starch biosynthesis in barley endosperm, we analyzed HvPho1 protein production and enzyme activity levels throughout barley endosperm development and characterized structure-function relationships of HvPho1. The molecular mechanisms underlying the initiation of starch granule biosynthesis, that is, the enzymes and substrates involved in the initial transition from simple sugars to polysaccharides, remain unclear. We found that HvPho1 is present as an active protein at the onset of barley endosperm development. Notably, purified recombinant protein can catalyze the de novo production of α-1,4-glucans using HvPho1 from G1P as the sole substrate. The structural properties of HvPho1 provide insights into the low affinity of HvPho1 for large polysaccharides like starch or amylopectin. Our results suggest that HvPho1 may play a role during the initiation of starch biosynthesis in barley.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Chloroplast Proteins); 0 (Glucosephosphates); 9005-25-8 (Starch); CIX3U01VAU (glucose-1-phosphate); EC 2.4.1.- (Starch Phosphorylase)


  10 / 580 MEDLINE  
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PMID:28325834
Autor:Rutsdottir G; Härmark J; Weide Y; Hebert H; Rasmussen MI; Wernersson S; Respondek M; Akke M; Højrup P; Koeck PJB; Söderberg CAG; Emanuelsson C
Endereço:From the Departments of Biochemistry and Structural Biology and.
Título:Structural model of dodecameric heat-shock protein Hsp21: Flexible N-terminal arms interact with client proteins while C-terminal tails maintain the dodecamer and chaperone activity.
Fonte:J Biol Chem; 292(19):8103-8121, 2017 May 12.
ISSN:1083-351X
País de publicação:United States
Idioma:eng
Resumo:Small heat-shock proteins (sHsps) prevent aggregation of thermosensitive client proteins in a first line of defense against cellular stress. The mechanisms by which they perform this function have been hard to define due to limited structural information; currently, there is only one high-resolution structure of a plant sHsp published, that of the cytosolic Hsp16.9. We took interest in Hsp21, a chloroplast-localized sHsp crucial for plant stress resistance, which has even longer N-terminal arms than Hsp16.9, with a functionally important and conserved methionine-rich motif. To provide a framework for investigating structure-function relationships of Hsp21 and understanding these sequence variations, we developed a structural model of Hsp21 based on homology modeling, cryo-EM, cross-linking mass spectrometry, NMR, and small-angle X-ray scattering. Our data suggest a dodecameric arrangement of two trimer-of-dimer discs stabilized by the C-terminal tails, possibly through tail-to-tail interactions between the discs, mediated through extended I V I motifs. Our model further suggests that six N-terminal arms are located on the outside of the dodecamer, accessible for interaction with client proteins, and distinct from previous undefined or inwardly facing arms. To test the importance of the I V I motif, we created the point mutant V181A, which, as expected, disrupts the Hsp21 dodecamer and decreases chaperone activity. Finally, our data emphasize that sHsp chaperone efficiency depends on oligomerization and that client interactions can occur both with and without oligomer dissociation. These results provide a generalizable workflow to explore sHsps, expand our understanding of sHsp structural motifs, and provide a testable Hsp21 structure model to inform future investigations.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Arabidopsis Proteins); 0 (Chloroplast Proteins); 0 (HSP16.9 protein, Triticum aestivum); 0 (HSP21 protein, Arabidopsis); 0 (Heat-Shock Proteins); 0 (Molecular Chaperones); 0 (Plant Proteins); 0 (Recombinant Proteins)



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