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| 2. |
- Hjortswang, H I, et al.
(författare)
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KNOTTED1-like homeobox genes of a gymnosperm, Norway spruce, expressed during somatic embryogenesis
- 2002
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Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 40:10, s. 837-843
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Tidskriftsartikel (refereegranskat)abstract
- Two Norway spruce (Picea abies (L.) Karst.) genes belonging to class I of the KNOTTED1-like homeobox (KNOX) genes, HBK2 and HBK3, were cloned with PCR-based methods. The expression of these and a previously characterised related gene, HBK1, in different organs and during somatic embryogenesis was studied with RTPCR. Transcripts of all three genes were detected in stems, roots and in cone buds, but not in needles. HBK1 and HBK3 are expressed throughout development in a normal cell line with embryogenic potential and in a cell line unable to form somatic embryos. HBK2 is expressed in the normal cell line, but not in the developmentally arrested cell line. This suggests that the HBK2 gene is involved in the somatic embryo development.
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| 3. |
- Ciereszko, I, et al.
(författare)
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Glucose and mannose regulate the expression of a major sucrose synthase gene in Arabidopsis via hexokinase-dependent mechanisms
- 2002
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Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 40:11, s. 907-911
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Tidskriftsartikel (refereegranskat)abstract
- Sucrose synthase (SuSy) is an important enzyme involved in sucrose synthesis/breakdown in all plants. Sus1, a major SuSy gene in Arabidopsis thaliana, was upregulated by sucrose, glucose and D-mannose, but not 3-O-methylglucose, when those compounds were fed to excised leaves. Mannos, was more effective than glucose or sucrose in the induction of Sus1, with strong effects observed at a concentration as low as 20, mM. When fed to the excised leaves, N-acetyl-glucosamine, an inhibitor of hexokinase (HXK) enzymatic activity, decreased sucrose- and glucose-dependent, but not mannose-dependent, upregulation of Sus1. The sucrose/glucose-dependent Sus1 expression was strongly induced in transgenic Arabidopsis HXK-overexpressing (OE) plants, whereas mannose-dependent Sus1 expression markedly decreased in OE, but not in HXK-"antisense", Arabidopsis plants. Feeding with sucrose resulted in a marked increase of glucose content in leaves, suggesting that it is glucose rather than sucrose that serves as a signal in upregulating Sus1 expression in sucrose-fed plants. The data suggest that Sus1 is regulated by a HXK-dependent pathway, with glucose and mannose effects differentially sensed/transmitted via the HXK step. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.
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| 4. |
- Gadjieva, Rena, et al.
(författare)
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Nonsense-mediated mRNA decay in barley mutants allows the cloning of mutated genes by a microarray approach.
- 2004
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Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 1873-2690 .- 0981-9428. ; 42:7-8, s. 681-685
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Tidskriftsartikel (refereegranskat)abstract
- We have previously described a microarray approach to identify and clone genes from mutants of higher organisms. In the method cDNA of two mutants with similar phenotype are competitively hybridized to DNA clones arrayed on a glass slide. Clones corresponding to an mRNA that is not expressed in one of the strains due to a mutation will be specifically highlighted in the hybridization, which provides a possibility to identify and eventually clone the mutated gene. The approach is dependent on mutations that affect the amount of mRNA. Nonsense mutations, which prematurely terminate translation, can be such mutations as a surveillance system known as nonsense-mediated decay (NMD) has been developed by organisms to reduce the abundance of mRNA with nonsense codons. In the present study, we have analysed the barley (Hordeum vulgare L.) magnesium chelatase mutants xantha-f 26, xantha-f 27 and xantha-f 40 in order to investigate the presence of NMD in barley, as well as the importance of the position of the stop codon for NMD. Both nonsense-mutants xantha-f 27 and xantha-f 40, but not the missense mutant xantha-f 26, showed NMD. This was not expected for xantha-f 27 as its mutation is in the last exon of the gene. We conclude the NMD expands the number of mutants that can be used for gene cloning by our described microarray approach.
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| 5. |
- Igamberdiev, A U, et al.
(författare)
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Capacity for NADPH/NADP turnover in the cytosol of barley seed endosperm : The role of NADPH-dependent hydroxypyruvate reductase
- 2000
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Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 38:10, s. 747-753
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Tidskriftsartikel (refereegranskat)abstract
- Barley (Hordeum vulgare L.) endosperm from developing seeds was found to contain relatively high activities of cytosolic NAD(P)II-dependent hydroxypyruvate reductase (HPR-2) and isocitrate dehydrogenase (ICDH). In contrast, activities of peroxisomal NADH-dependent hydroxypyruvate reductase (HPR-1) and glycolate oxidase as well as cytosolic NAD(P)H-dependent glyoxylate reductase were very low or absent in the endosperm both during maturation and seed germination, indicating the lack of a complete glycolate cycle in this tissue. In addition, activities of cytosolic glucose-6-phosphate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase were low or absent in the endosperm. The endosperm HPR-2 exhibited similar properties to those of an earlier described HPR-2 from green leaves, e.g. activities with both hydroxypyruvate and glyoxylate, utilization of both NADPH and NADH as cofactors, and a strong uncompetitive inhibition by oxalate (K-i in the order of micromolar). In etiolated leaves, both HPR-1 and HPR-2 were present with the same activity as in green leaves, indicating that the lack of HPR-I in the endosperm is not a general feature of non-photosynthetic tissues. We conclude that the endosperm has considerable capacity for cytosolic NADP/NADPH cycling via HPR-2 and ICDH, the former being possibly involved in the utilization of a serine-derived carbon. (C) 2000 Editions scientifiques et medicales Elsevier SAS.
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| 6. |
- Kleczkowski, Leszek A, 1954-
(författare)
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A new player in the starch field
- 2001
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Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 39:9, s. 759-761
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Tidskriftsartikel (refereegranskat)abstract
- A possible role of a newly discovered ADP-glucose pyrophosphatase (AGPPase) is discussed in the context of starch synthesis. The enzyme hydrolyses ADP-glucose (starch precursor) and may potentially divert the flow of carbon from starch synthase, resulting in a 'futile cycle' when 'coupled' with ADP-glucose pyrophosphorylase. The activity of AGPPase is inversely related to starch yield in sink tissues, and may be prone to inhibition by Pi and certain other products of the starch pathway. The AGPPase likely belongs to a `nudix' family of enzymes that in animal tissues and yeast are known to regulate levels of activated sugars. Some strategies for future research are underlined. (C) 2001 Editions scientifiques et medicales Elsevier SAS.
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| 7. |
- Matic, Sandra, et al.
(författare)
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Sucrose synthase isoforms in cultured tobacco cells
- 2004
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Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 1873-2690 .- 0981-9428. ; 42:4, s. 299-306
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Tidskriftsartikel (refereegranskat)abstract
- The plant enzyme sucrose synthase (SuSy; EC 2.4.1.13) catalyzes the reversible conversion of sucrose and UDP into UDP-glucose (UDP-Glc) and fructose. The enzyme exists in different isoforms and is both located in the cytosol, membrane-bound and associated to the actin cytoskeleton. We here investigate sucrose synthase from tobacco (Nicotiana tabacum L.) BY-2 heterotrophic cell suspensions. Two different isoforms of sucrose synthase SuSy1 and SuSy2, could be purified from cytosolic extracts of these cells using a combination of poly(ethylene glycol) (PEG) precipitation, gel filtration, ion-exchange chromatography and affinity chromatography. They were clearly distinct. both with regard to the binding to the ion-exchange column and with regard to their kinetic and regulatory properties. SuSy 1, the more abundant species, showed lower V-max and K-m for sucrose and UDP compared to the less abundant SuSy2. The activity of SuSy2 in the breakdown direction was stimulated by 60% by actin, in contrast to that of SuSy 1, which showed a 17% inhibition. An indication of interaction between SuSy I and actin was obtained by partitioning in aqueous Dextran-PEG two-phase systems. Furthermore, fructose 2,6-bisphosphate (F26BP) at micromolar concentrations stimulated SuSy2 in the presence of actin while SuSy I was strongly inhibited by fructose. Possible roles of these two isoforms in the sucrose turnover in BY-2 cells are discussed. (C) 2004 Elsevier SAS. All rights reserved.
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| 8. |
- Olsson, Ulf, et al.
(författare)
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Characterization of eight barley xantha-f mutants deficient in magnesium chelatase
- 2004
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Ingår i: Plant Physiology and Biochemistry. - : Elsevier BV. - 1873-2690 .- 0981-9428. ; 42:6, s. 557-564
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Tidskriftsartikel (refereegranskat)abstract
- Magnesium chelatase (EC 6.6.1.1) catalyses the insertion of magnesium into protoporphyrin IX, the first unique step of the chlorophyll biosynthetic pathway. The enzyme is composed of three different subunits of approximately 40, 70 and 140 kDa. In barley (Hordeum vulgare L.) the subunits are encoded by the genes Xantha-h, Xantha-g and Xantha-f. In the 1950s, eight induced xantha-f mutants were isolated. In this work we characterized these mutations at the DNA level and provided explanations for their phenotypes. The xantha-f10 mutation is a 3 bp deletion, resulting in a polypeptide lacking the glutamate residue at position 424. The leaky mutation xantha-f26 has a missense mutation leading to a M632R exchange. The xantha-f27 and -f40 are deletions of 14 and 2 bp, respectively, resulting in truncated polypeptides of 1104 and 899 amino acid residues, respectively. Mutation xantha-f41 is an in-frame deletion that removes A439, L440, Q441 and V442 from the resulting protein. Mutation xantha-f58 is most likely a deletion of the whole Xantha-f gene, as no DNA fragments could be detected by PCR or southern blot experiments. The slightly leaky xantha-f60 and non-leaky -f68 mutations each have a missense mutation causing a P393L and G794E exchange in the polypeptide, respectively.
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| 9. |
- Sävenstrand, Helena, et al.
(författare)
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Six genes strongly regulated by mercury in Pisum sativum roots
- 2004
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Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 42:2, s. 135-142
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Tidskriftsartikel (refereegranskat)abstract
- Suppression subtractive hybridisation was used to isolate heavy metal-induced genes from Pisum sativum roots hydroponically exposed to 5 microM HgCl2 and 10 microM EDTA. Six genes were induced out of which one, PsHMIP6B, was novel. The other genes (PsSAMT, PsI2'H, PsNDA, PsAPSR, PsPOD) had not previously been isolated from pea and sequenced. All six genes were also induced after exposure to 5 microM HgCl2 in the absence of EDTA. The induction pattern was in some cases different for the two Hg species, demonstrating a quicker response to-free Hg2+ than Hg-EDTA. The stress-specificity of the gene regulation was investigated by hydroponically adding 5 microM Cd2+. Most Hg-induced cDNAs were also induced by Cd2+ but to a smaller extent than after Hg exposure. In addition, the gene expression was also probed for tissue specificity, which showed that all six genes were expressed in roots and not in leaves.
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| 10. |
- Sävenstrand, Helena, et al.
(författare)
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Ultraviolet-B signalling : Arabidopsis brassinosteroid mutants are defective in UV-B regulated defence gene expression
- 2004
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Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 42:9, s. 687-694
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Tidskriftsartikel (refereegranskat)abstract
- The involvement of brassinosteroids in signalling events in plants during UV-B stress (280-315 nm) was investigated in Arabidopsis thaliana. Brassinosteroids are involved in growth and development in plants and have also been shown to enhance stress tolerance. Three mutants deficient in the biosynthetic pathway of brassinolide (BL; det2, dim1 and cpd) and the BL insensitive mutant (bri1) were together with visible light irradiated with 3 or 9 h of UV-B radiation (biologically effective radiation normalised to 300 nm being 0.24 W m(-2)). Also, a small size control, irx1, and Columbia 0 (Col-0) wild-type plants were examined under identical conditions. Gene expression patterns were established for these mutants with a set of four molecular markers (the defence genes chalcone synthase (CHS), PYROA, pathogenesis-related protein PR-5, and a gene regulated by very low levels of UV-B, MEB5.2). Although the genes in the brassinodefective mutants were still induced by UV-B radiation, they all also showed reduced levels of mRNA transcripts compared with Col-0 and irx1. The bri1 and cpd were the mutants with lowest levels of molecular marker mRNA transcripts. The effects of impairment of brassinosteroid signalling also differed between the genes studied, indicating a need for a complete brassinosteroid pathway in UV-B signalling.
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