| 1. |
- Meng, Meng, et al.
(författare)
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UDP-glucose pyrophosphorylase is not rate limiting, but is essential in arabidopsis
- 2009
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Ingår i: Plant and Cell Physiology. - Kyoto : Japanese society of plant physiologists. - 0032-0781 .- 1471-9053. ; 50:5, s. 998-1011
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Tidskriftsartikel (refereegranskat)abstract
- UDP-glucose pyrophosphorylase (UGPase) produces UDP-glucose which is essential for sucrose and polysaccharide synthesis. Using Arabidopsis, we demonstrated that two UGPase genes (UGP1 and UGP2) are differentially expressed in a variety of organs, with UGP1 being pre-dominant. Co-expression analyses of UGP genes suggest that UGP1 is closely co-regulated with carbohydrate metabolism genes, late embryogenesis and seed loading, while UGP2 is co-regulated with stress response genes, fertilized flowers and photosynthetic genes. We have used Arabidopsis mutants for the UGP genes to characterize the role of both genes. The UGPase activity/protein was reduced by 70, 10 and 85% in ugp1, ugp2 and ugp1/ugp2 double mutant (DK) plants, respectively. A decrease in UGPase activity/protein was accompanied by an increase in expression of USP, a gene for UDP-sugar pyrophos-phorylase, suggesting a compensatory mechanism. Generally, the mutants had no effects on soluble sugar/starch content (except in certain cases for DK plants), and there were no differences in cell wall composition/content between the wild type and the mutants. On the other hand, DK plants had greater hypocotyl and root lengths. When grown in the field, the mutants had as much as a 50% decrease in the number of seeds produced (consistent with a substantial decrease in field fitness), suggesting that they would be outcompeted in the field in a few generations. Overall, the data suggest that UGPase is not rate limiting for sucrose/starch and cell wall synthesis, but that it is essential in Arabidopsis.
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| 2. |
- Khrouchtchova, Anastassia, et al.
(författare)
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A previosly found thylakoid membrane protein of 14 kDa (TMP14) is a novel subunit of photosystem I and is designated PSI-P
- 2005
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793. ; 579:21, s. 4808-4812
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Tidskriftsartikel (refereegranskat)abstract
- We show that the thylakoid membrane phosphoprotein TMP14 is a novel subunit of plant photosystem I (PSI). Blue native/SDS–PAGE and sucrose gradient fractionation demonstrated the association of the protein exclusively with PSI. We designate the protein PSI-P. The presence of PSI-P subunit in Arabidopsis mutants lacking other PSI subunits was analyzed and suggested a location in the proximity of PSI-L, -H and -O subunits. The PSI-P protein was not differentially phosphorylated in state 1 and state 2.
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| 3. |
- Klimmek, Frank, et al.
(författare)
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Structure of the higher plant light harvesting complex I : in vivo characterization and structural interdependence of the Lhca proteins.
- 2005
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Ingår i: Biochemistry. - 0006-2960. ; 44:8, s. 3065-73
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the structure of the higher plant light harvesting complex of photosystem I (LHCI) by analyzing PSI-LHCI particles isolated from a set of Arabidopsis plant lines, each lacking a specific Lhca (Lhca1-4) polypeptide. Functional antenna size measurements support the recent finding that there are four Lhca proteins per PSI in the crystal structure [Ben-Shem, A., Frolow, F., and Nelson, N. (2003) Nature 426, 630-635]. According to HPLC analyses the number of pigment molecules bound within the LHCI is higher than expected from reconstitution studies or analyses of isolated native LHCI. Comparison of the spectra of the particles from the different lines reveals chlorophyll absorption bands peaking at 696, 688, 665, and 655 nm that are not present in isolated PSI or LHCI. These bands presumably originate from "gap" or "linker" pigments that are cooperatively coordinated by the Lhca and/or PSI proteins, which we have tentatively localized in the PSI-LHCI complex.
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| 4. |
- Vainonen, Julia P., et al.
(författare)
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Light regulation of CaS, a novel phosphoprotein in the thylakoid membrane of Arabidopsis thaliana
- 2008
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 275:8, s. 1767-1777
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Tidskriftsartikel (refereegranskat)abstract
- Exposure of Arabidopsis thaliana plants to high levels of light revealed specific phosphorylation of a 40 kDa protein in photosynthetic thylakoid membranes. The protein was identified by MS as extracellular calcium-sensing receptor (CaS), previously reported to be located in the plasma membrane. By confocal laser scanning microscopy and subcellular fractionation, it was demonstrated that CaS localizes to the chloroplasts and is enriched in stroma thylakoids. The phosphorylation level of CaS responded strongly to light intensity. The light-dependent thylakoid protein kinase STN8 is required for CaS phosphorylation. The phosphorylation site was mapped to the stroma-exposed Thr380, located in a motif for interaction with 14-3-3 proteins and proteins with forkhead-associated domains, which suggests the involvement of CaS in stress responses and signaling pathways. The knockout Arabidopsis lines revealed a significant role for CaS in plant growth and development. © 2008 The Authors.
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