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Selstam, Eva
Publications (10 of 32) Show all publications
Sheng, M., Hosseinzadeh, A., Muralidharan, S. V., Gaur, R., Selstam, E. & Tuck, S. (2015). Aberrant Fat Metabolism in Caenorhabditis elegans Mutants with Defects in the Defecation Motor Program. PLoS ONE, 10(4), Article ID e0124515.
Open this publication in new window or tab >>Aberrant Fat Metabolism in Caenorhabditis elegans Mutants with Defects in the Defecation Motor Program
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2015 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 4, article id e0124515Article in journal (Refereed) Published
Abstract [en]

The molecular mechanisms by which dietary fatty acids are absorbed by the intestine, and the way in which the process is regulated are poorly understood. In a genetic screen for mutations affecting fat accumulation in the intestine of Caenorhabditis elegans, nematode worms, we have isolated mutations in the aex-5 gene, which encodes a Kex2/subtilisinfamily, Ca2+-sensitive proprotein convertase known to be required for maturation of certain neuropeptides, and for a discrete step in an ultradian rhythmic phenomenon called the defecation motor program. We demonstrate that aex-5 mutants have markedly lower steadystate levels of fat in the intestine, and that this defect is associated with a significant reduction in the rate at which labeled fatty acid derivatives are taken up from the intestinal lumen. Other mutations affecting the defecation motor program also affect steady-state levels of triglycerides, suggesting that the program is required per se for the proper accumulation of neutral lipids. Our results suggest that an important function of the defecation motor program in C. elegans is to promote the uptake of an important class of dietary nutrients. They also imply that modulation of the program might be one way in which worms adjust nutrient uptake in response to altered metabolic status.

Place, publisher, year, edition, pages
PLOS one, 2015
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-103146 (URN)10.1371/journal.pone.0124515 (DOI)000352477800268 ()25849533 (PubMedID)
Funder
Swedish Cancer Society, 12 0534
Note

supported by grants from Vetenskapsrådet (K2012-67X-20441-063) and Cancerfonden (12 0534).

Available from: 2015-05-29 Created: 2015-05-18 Last updated: 2018-06-07Bibliographically approved
Zhang, L., Selao, T. T., Selstam, E. & Norling, B. (2015). Subcellular Localization of Carotenoid Biosynthesis in Synechocystis sp PCC 6803. PLoS ONE, 10(6), Article ID e0130904.
Open this publication in new window or tab >>Subcellular Localization of Carotenoid Biosynthesis in Synechocystis sp PCC 6803
2015 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 6, article id e0130904Article in journal (Refereed) Published
Abstract [en]

The biosynthesis pathway of carotenoids in cyanobacteria is partly described. However, the subcellular localization of individual steps is so far unknown. Carotenoid analysis of different membrane subfractions in Synechocystis sp. PCC6803 shows that "light" plasma membranes have a high carotenoid/protein ratio, when compared to "heavier" plasma membranes or thylakoids. The localization of CrtQ and CrtO, two well-defined carotenoid synthesis pathway enzymes in Synechocystis, was studied by epitope tagging and western blots. Both enzymes are locally more abundant in plasma membranes than in thylakoids, implying that the plasma membrane has higher synthesis rates of beta-carotene precursor molecules and echinenone.

National Category
Botany
Identifiers
urn:nbn:se:umu:diva-106601 (URN)10.1371/journal.pone.0130904 (DOI)000356567400164 ()26083372 (PubMedID)
Available from: 2015-07-28 Created: 2015-07-24 Last updated: 2018-06-07Bibliographically approved
Selstam, E., Brain, A. P. & Williams, W. P. (2011). The relationship between different spectral forms of the protochlorophyllide oxidoreductase complex and the structural organisation of prolamellar bodies isolated from Zea mays. Photosynthesis Research, 108(1), 47-59
Open this publication in new window or tab >>The relationship between different spectral forms of the protochlorophyllide oxidoreductase complex and the structural organisation of prolamellar bodies isolated from Zea mays
2011 (English)In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 108, no 1, p. 47-59Article in journal (Refereed) Published
Abstract [en]

Incubation of prolamellar bodies (PLB) in high-salt media leads to changes in PLB structure and properties of their protochlorophyllide oxidoreductase-protochlorophyllide (POR-PChlide) complex. The paracrystalline organisation typical of PLB is disrupted and NADPH dissociates from photoconvertible POR-PChlide, with absorption maxima at 640 and 650 nm (POR-PChlide ( 640/650 )), and a non-photoconvertible form, with absorption maxima at 635 nm (POR-PChlide ( 635 )), is formed. These effects are strongly dependent on the valence of the cation of the perturbing salt, indicating that they involve surface double layers effects. They are also influenced by the nature of the anion and by high concentrations of non-electrolytes, suggesting the involvement of surface hydration effects. The structural changes are largely, if not entirely, independent of the presence of excess NADPH. Changes to the POR-PChlide complex, however, are strongly inhibited by excess NADPH suggesting that the two sets of changes may not be causally linked. As long as the disruption is not too great, the structural changes seen on incubation of PLB in high salt media lacking excess NADPH are reversed on removal of the high salt perturbation. This reversal is independent of the presence or absence of added NADPH. Reformation of photoconvertible POR-PChlide, however, requires the presence of NADPH. The reformation of paracrystalline PLB in the absence of NADPH strongly indicates that preservation of PLB structure, in isolated PLB preparations at least, is independent of the presence or absence of POR-PChlide ( 650 ).

Keywords
protochlorophyllide oxidoreductase, prolamellar body, protochlorophyllide, chlorophyllide, cubic membrane
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-44329 (URN)10.1007/s11120-011-9653-1 (DOI)21505944 (PubMedID)
Available from: 2011-05-31 Created: 2011-05-31 Last updated: 2018-06-08Bibliographically approved
Szilágyi, A., Selstam, E. & Åkerlund, H.-E. (2008). Laurdan fluorescence spectroscopy in the thylakoid bilayer: The effect of violaxanthin to zeaxanthin conversion on the galactolipid dominated lipid environment.. Biochimica et Biophysica Acta, 1778(1), 348-355
Open this publication in new window or tab >>Laurdan fluorescence spectroscopy in the thylakoid bilayer: The effect of violaxanthin to zeaxanthin conversion on the galactolipid dominated lipid environment.
2008 (English)In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1778, no 1, p. 348-355Article in journal (Refereed) Published
Abstract [en]

Laurdan (6-lauroyl-2-dimethylaminonaphthalene) fluorescence spectroscopy has been applied to probe the physical status of the thylakoid membrane upon conversion of violaxanthin to zeaxanthin. So far, only phospholipid-dominated membranes have been studied by this method and hereby we report the first use of laurdan in mono- and digalactosyldiacylglycerol-dominated membrane systems. The generalised polarisation (GP) of laurdan was used as a measure of the structural effect of xanthophyll cycle pigments in isolated spinach (Spinacia oleracea) thylakoids and in model membrane vesicles composed of chloroplast galactolipids. Higher GP values indicate a membrane in a more ordered structure, whereas lower GP values point to a membrane in a less ordered fluid phase. The method was used to probe the effect of violaxanthin and zeaxanthin in thylakoid membranes at different temperatures. At 4, 25 and 37 °C the GP values for dark-adapted thylakoids in the violaxanthin-form were 0.55, 0.28 and 0.26. After conversion of violaxanthin to zeaxanthin, at the same temperatures, the GP values were 0.62, 0.36 and 0.34, respectively. GP values increased gradually upon conversion of violaxanthin to zeaxanthin. Similar results were obtained in the liposomal systems in the presence of these xanthophyll cycle pigments. We conclude from these results that the conversion of violaxanthin to zeaxanthin makes the thylakoid membrane more ordered.

Place, publisher, year, edition, pages
Elsevier, 2008
Keywords
2-Naphthylamine/*analogs & derivatives/chemistry, Fatty Acids/analysis, Galactolipids/*metabolism, Laurates/*chemistry, Lipid Bilayers/*chemistry, Liposomes, Spectrometry; Fluorescence, Spinacia oleracea, Temperature, Thylakoids/*chemistry, Xanthophylls/chemistry/*metabolism
Identifiers
urn:nbn:se:umu:diva-9499 (URN)10.1016/j.bbamem.2007.10.006 (DOI)000253269500037 ()17980143 (PubMedID)
Available from: 2008-05-27 Created: 2008-05-27 Last updated: 2019-08-07Bibliographically approved
Selstam, E., Schelin, J., Williams, W. P. & Brain, A. P. (2007). Structural organisation of prolamellar bodies (PLB) isolated from Zea mays. Parallel TEM, SAXS and absorption spectra measurements on samples subjected to freeze-thaw, reduced pH and high-salt perturbation.. Biochimica et Biophysica Acta, 1768, 2235-2245
Open this publication in new window or tab >>Structural organisation of prolamellar bodies (PLB) isolated from Zea mays. Parallel TEM, SAXS and absorption spectra measurements on samples subjected to freeze-thaw, reduced pH and high-salt perturbation.
2007 (English)In: Biochimica et Biophysica Acta, ISSN 0006-3002, Vol. 1768, p. 2235-2245Article in journal (Refereed) Published
Abstract [en]

Well-organised PLB gives rise to a X-ray diffraction pattern overlaid by a scattering pattern arising from individual tubules within less well-organised regions of the lattice. TEM and SAXS measurements were used to characterise the structural changes in PLB subjected to perturbation by freeze–thaw, exposure to pH 6.5, or resuspension in high-salt media. Comparison of SAXS patterns measured, before and after structural perturbation allows the separation of the contributions from ordered and disordered PLB. The diffraction pattern is shown to be based on a diamond cubic (Fd3m) lattice of unit cell a = 78 nm. Freeze–thaw and high-salt disruption lead to the breakdown of ordered PLB into disordered tubules of similar dimensions to those making up the original PLB lattice. Their scattering patterns suggest that they are approximately 26 nm in diameter with a central lumen about 16 nm in diameter. The tubules formed at pH 6.5 are appreciably narrower, probably reflecting changes in the pattern of ionisation of charged groups at the membrane surface. Absorption spectra of PLB in media containing different concentrations of salts indicated that the structural and spectral changes are related. NADPH, have a significant role in the protection of POR-PChlide650 but to have only a relatively small effect on the preservation of PLB organisation indicating that the retention of POR-PChlide650 in isolated PLB preparations is a poor guide to their structural integrity.

Identifiers
urn:nbn:se:umu:diva-15865 (URN)doi:10.1016/j.bbamem.2007.05.005 (DOI)17559801 (PubMedID)
Available from: 2007-09-18 Created: 2007-09-18 Last updated: 2018-06-09Bibliographically approved
Ivanov, A. G., Krol, M., Selstam, E., Sane, P. V., Sveshnikov, D., Park, Y.-I., . . . Huner, N. P. (2007). The induction of CP43' by iron-stress in Synechococcus sp. PCC 7942 is associated with carotenoid accumulation and enhanced fatty acid unsaturation.. Biochimica et Biophysica Acta, 1767(6), 807-13
Open this publication in new window or tab >>The induction of CP43' by iron-stress in Synechococcus sp. PCC 7942 is associated with carotenoid accumulation and enhanced fatty acid unsaturation.
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2007 (English)In: Biochimica et Biophysica Acta, ISSN 0006-3002, Vol. 1767, no 6, p. 807-13Article in journal (Refereed) Published
Abstract [en]

Comparative lipid analysis demonstrated reduced amount of PG (50%) and lower ratio of MGDG/DGDG in iron-stressed Synechococcus sp. PCC 7942 cells compared to cells grown under iron sufficient conditions. In parallel, the monoenoic (C:1) fatty acids in MGDG, DGDG and PG increased from 46.8%, 43.7% and 45.6%, respectively in control cells to 51.6%, 48.8% and 48.7%, respectively in iron-stressed cells. This suggests increased membrane dynamics, which may facilitate the diffusion of PQ and keep the PQ pool in relatively more oxidized state in iron-stressed compared to control cells. This was confirmed by chlorophyll fluorescence and thermoluminescence measurements. Analysis of carotenoid composition demonstrated that the induction of isiA (CP43′) protein in response to iron stress is accompanied by significant increase of the relative abundance of all carotenoids. The quantity of carotenoids calculated on a Chl basis increased differentially with nostoxanthin, cryptoxanthin, zeaxanthin and β-carotene showing 2.6-, 3.1-, 1.9- and 1.9-fold increases, respectively, while the relative amount of caloxanthin was increased only by 30%. HPLC analyses of the pigment composition of Chl–protein complexes separated by non-denaturating SDS-PAGE demonstrated even higher relative carotenoids content, especially of cryptoxanthin, in trimer and monomer PSI Chl–protein complexes co-migrating with CP43′ from iron-stressed cells than in PSI complexes from control cells where CP43′ is not present. This implies a carotenoid-binding role for the CP43′ protein which supports our previous suggestion for effective energy quenching and photoprotective role of CP43′ protein in cyanobacteria under iron stress.

Identifiers
urn:nbn:se:umu:diva-15862 (URN)doi:10.1016/j.bbabio.2007.02.006 (DOI)17362874 (PubMedID)
Available from: 2007-08-03 Created: 2007-08-03 Last updated: 2018-06-09Bibliographically approved
Hendrickson, L., Vlcková, A., Selstam, E., Huner, N., Öquist, G. & Hurry, V. (2006). Cold acclimation of the Arabidopsis dgd1 mutant results in recovery from photosystem I-limited photosynthesis.. FEBS Letters, 580(20), 4959-68
Open this publication in new window or tab >>Cold acclimation of the Arabidopsis dgd1 mutant results in recovery from photosystem I-limited photosynthesis.
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2006 (English)In: FEBS Letters, ISSN 0014-5793, Vol. 580, no 20, p. 4959-68Article in journal (Refereed) Published
Abstract [en]

We compared the thylakoid membrane composition and photosynthetic properties of non- and cold-acclimated leaves from the dgd1 mutant (lacking >90% of digalactosyl–diacylglycerol; DGDG) and wild type (WT) Arabidopsis thaliana. In contrast to warm grown plants, cold-acclimated dgd1 leaves recovered pigment-protein pools and photosynthetic function equivalent to WT. Surprisingly, this recovery was not correlated with an increase in DGDG. When returned to warm temperatures the severe dgd1 mutant phenotype reappeared. We conclude that the relative recovery of photosynthetic activity at 5 °C resulted from a temperature/lipid interaction enabling the stable assembly of PSI complexes in the thylakoid.

Keywords
Acclimatization/*physiology, Arabidopsis/anatomy & histology/*physiology, Arabidopsis Proteins/genetics/*metabolism, Cold, Galactosyltransferases/genetics/*metabolism, Lipids/chemistry, Phenotype, Photosynthesis/*physiology, Photosystem I Protein Complex/*physiology, Random Allocation, Thylakoids/chemistry/ultrastructure
Identifiers
urn:nbn:se:umu:diva-15839 (URN)doi:10.1016/j.febslet.2006.07.081 (DOI)16930596 (PubMedID)
Available from: 2007-08-03 Created: 2007-08-03 Last updated: 2018-06-09Bibliographically approved
Ivanov, A. G., Hendrickson, L., Krol, M., Selstam, E., Öquist, G., Hurry, V. & Huner, N. P. (2006). Digalactosyl-diacylglycerol deficiency impairs the capacity for photosynthetic intersystem electron transport and state transitions in Arabidopsis thaliana due to photosystem I acceptor-side limitations.. Plant Cell Physiology, 47(8), 1146-57
Open this publication in new window or tab >>Digalactosyl-diacylglycerol deficiency impairs the capacity for photosynthetic intersystem electron transport and state transitions in Arabidopsis thaliana due to photosystem I acceptor-side limitations.
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2006 (English)In: Plant Cell Physiology, ISSN 0032-0781, Vol. 47, no 8, p. 1146-57Article in journal (Refereed) Published
Abstract [en]

Compared with wild type, the dgd1 mutant of Arabidopsis thaliana exhibited a lower amount of PSI-related Chl–protein complexes and lower abundance of the PSI-associated polypeptides, PsaA, PsaB, PsaC, PsaL and PsaH, with no changes in the levels of Lhca1–4. Functionally, the dgd1 mutant exhibited a significantly lower light-dependent, steady-state oxidation level of P700 (P700+) in vivo, a higher intersystem electron pool size, restricted linear electron transport and a higher rate of reduction of P700+ in the dark, indicating an increased capacity for PSI cyclic electron transfer compared with the wild type. Concomitantly, the dgd1 mutant exhibited a higher sensitivity to and incomplete recovery of photoinhibition of PSI. Furthermore, dgd1 exhibited a lower capacity to undergo state transitions compared with the wild type, which was associated with a higher reduction state of the plastoquinone (PQ) pool. We conclude that digalactosyl-diacylglycerol (DGDG) deficiency results in PSI acceptor-side limitations that alter the flux of electrons through the photosynthetic electron chain and impair the regulation of distribution of excitation energy between the photosystems. These results are discussed in terms of thylakoid membrane domain reorganization in response to DGDG deficiency in A. thaliana.

Keywords
Arabidopsis/*physiology, Electron Transport/*physiology, Galactolipids/*deficiency/physiology, Photosynthesis, Photosystem I Protein Complex/*physiology, Thylakoids/physiology
Identifiers
urn:nbn:se:umu:diva-15827 (URN)doi:10.1093/pcp/pcj089 (DOI)16854937 (PubMedID)
Available from: 2007-08-03 Created: 2007-08-03 Last updated: 2018-06-09Bibliographically approved
Ivanov, A. G., Krol, M., Sveshnikov, D., Selstam, E., Sandström, S., Koochek, M., . . . Huner, N. P. (2006). Iron deficiency in cyanobacteria causes monomerization of photosystem I trimers and reduces the capacity for state transitions and the effective absorption cross section of photosystem I in vivo.. Plant Physiology, 141(4), 1436-45
Open this publication in new window or tab >>Iron deficiency in cyanobacteria causes monomerization of photosystem I trimers and reduces the capacity for state transitions and the effective absorption cross section of photosystem I in vivo.
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2006 (English)In: Plant Physiology, ISSN 0032-0889, Vol. 141, no 4, p. 1436-45Article in journal (Refereed) Published
Abstract [en]

The induction of the isiA (CP43') protein in iron-stressed cyanobacteria is accompanied by the formation of a ring of 18 CP43' proteins around the photosystem I (PSI) trimer and is thought to increase the absorption cross section of PSI within the CP43'-PSI supercomplex. In contrast to these in vitro studies, our in vivo measurements failed to demonstrate any increase of the PSI absorption cross section in two strains (Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803) of iron-stressed cells. We report that iron-stressed cells exhibited a reduced capacity for state transitions and limited dark reduction of the plastoquinone pool, which accounts for the increase in PSII-related 685 nm chlorophyll fluorescence under iron deficiency. This was accompanied by lower abundance of the NADP-dehydrogenase complex and the PSI-associated subunit PsaL, as well as a reduced amount of phosphatidylglycerol. Nondenaturating polyacrylamide gel electrophoresis separation of the chlorophyll-protein complexes indicated that the monomeric form of PSI is favored over the trimeric form of PSI under iron stress. Thus, we demonstrate that the induction of CP43' does not increase the PSI functional absorption cross section of whole cells in vivo, but rather, induces monomerization of PSI trimers and reduces the capacity for state transitions. We discuss the role of CP43' as an effective energy quencher to photoprotect PSII and PSI under unfavorable environmental conditions in cyanobacteria in vivo.

Keywords
Bacterial Proteins/*metabolism/physiology, Immunohistochemistry, Iron/*physiology, Light-Harvesting Protein Complexes/metabolism/physiology, Lipid Metabolism, NADPH Dehydrogenase/metabolism, Oxidation-Reduction, Phase Transition, Phosphatidylglycerols/metabolism, Photosystem I Protein Complex/*metabolism, Photosystem II Protein Complex/metabolism, Synechococcus/enzymology/*metabolism
Identifiers
urn:nbn:se:umu:diva-15863 (URN)doi:10.1104/pp.106.082339 (DOI)16798943 (PubMedID)
Available from: 2007-08-03 Created: 2007-08-03 Last updated: 2018-06-09Bibliographically approved
Selstam, E., Schelin, J., Brain, T. & Williams, W. P. (2002). The effects of low pH on the properties of protochlorophyllide oxidoreductase and the organization of prolamellar bodies of maize (Zea mays). European Journal of Biochemistry, 269(9), 2336-2346
Open this publication in new window or tab >>The effects of low pH on the properties of protochlorophyllide oxidoreductase and the organization of prolamellar bodies of maize (Zea mays)
2002 (English)In: European Journal of Biochemistry, ISSN 0014-2956, E-ISSN 1432-1033, Vol. 269, no 9, p. 2336-2346Article in journal (Refereed) Published
Abstract [en]

Prolamellar bodies (PLB) contain two photochemically active forms of the enzyme protochlorophyllide oxidoreductase POR-PChlide(640) and POR-PChlide(650) (the spectral forms of POR-Chlide complexes with absorption maxima at the indicated wavelengths). Resuspension of maize PLB in media with a pH below 6.8 leads to a rapid conversion of POR-PChlide(650) to POR-PChlide(640) and a dramatic re-organization of the PLB membrane system. In the absence of excess NADPH, the absorption maximum of the POR complex undergoes a further shift to about 635 nm. This latter shift is reversible on the re-addition of NADPH with a half-saturation value of about 0.25 mm NADPH for POR-PChlide(640) reformation. The disappearance of POR-PChlide(650) and the reorganization of the PLB, however, are irreversible. Restoration of low-pH treated PLB to pH 7.5 leads to a further breakdown down of the PLB membrane and no reformation of POR-PChlide(650) . Related spectral changes are seen in PLB aged at room temperature at pH 7.5 in NADPH-free assay medium. The reformation of POR-PChlide(650) in this system is readily reversible on re-addition of NADPH with a half-saturation value about 1.0 mum. Comparison of the two sets of changes suggest a close link between the stability of the POR-PChlide(650) , membrane organization and NADPH binding. The low-pH driven spectral changes seen in maize PLB are shown to be accelerated by adenosine AMP, ADP and ATP. The significance of this is discussed in terms of current suggestions of the possible involvement of phosphorylation (or adenylation) in changes in the aggregational state of the POR complex.

Keywords
protochlorophyllide oxidoreductase, prolamellar body, protochlorophyllide, oxidoreductase, chlorophyllide
Identifiers
urn:nbn:se:umu:diva-44684 (URN)10.1046/j.1432-1033.2002.02897.x (DOI)000175438100011 ()
Available from: 2011-08-10 Created: 2011-06-09 Last updated: 2018-06-08
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