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Dahlin, Clas
Publications (6 of 6) Show all publications
Aronsson, H., Sundqvist, C. & Dahlin, C. (2003). POR – import and membrane association of a key element in chloroplast development. Physiologia Plantarum: An International Journal for Plant Biology, 118(1), 1-9
Open this publication in new window or tab >>POR – import and membrane association of a key element in chloroplast development
2003 (English)In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 118, no 1, p. 1-9Article in journal (Refereed) Published
Abstract [en]

The development of proplastids or etioplasts to chloroplast is visualized by the accumulation of chlorophyll in leaves of higher plants. The biosynthesis of chlorophyll includes a light-dependent reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide). This light-dependent step is catalysed by the nucleus-encoded NADPH:Pchlide oxidoreductase (POR, EC 1.6.99.1). POR is active within plastids and therefore has to be translocated over the plastid envelope membranes. The import of chloroplast proteins seems to follow a general import pathway using translocons at the outer and inner envelope membrane. POR cross-linking to Toc75, one of the major translocon components at the outer envelope membrane, indicates its use of the general import pathway. However, since variations exist within the so-called general import pathway one has to consider previous data suggesting a novel totally Pchlide-dependent import pathway of one POR isoform, PORA. The suggested Pchlide dependency of POR import is discussed since recent observations contradict this idea. In the stroma the POR transit peptide is cleaved off and the mature POR protein is targeted to the plastid inner membranes. The correct and stable association of POR to the membrane requires the cofactor NADPH. Functional activity of POR calls for formation of an NADPH–Pchlide–POR complex, a formation that probably takes place after the membrane association and is dependent on a phosphorylation reaction.

Place, publisher, year, edition, pages
Blackwell Publishing, 2003
Keywords
POR, Chloroplast development
National Category
Biological Sciences
Identifiers
urn:nbn:se:hh:diva-420 (URN)10.1034/j.1399-3054.2003.00088.x (DOI)000182307300001 ()2-s2.0-0038707432 (Scopus ID)2082/758 (Local ID)2082/758 (Archive number)2082/758 (OAI)
Available from: 2007-01-23 Created: 2007-01-23 Last updated: 2018-03-23Bibliographically approved
Aronsson, H., Sundqvist, C. & Dahlin, C. (2003). POR hits the road: import and assembly of a plastid protein. Plant Molecular Biology, 51(1), 1-7
Open this publication in new window or tab >>POR hits the road: import and assembly of a plastid protein
2003 (English)In: Plant Molecular Biology, ISSN 0167-4412, E-ISSN 1573-5028, Vol. 51, no 1, p. 1-7Article in journal (Refereed) Published
Abstract [en]

The biosynthesis of chlorophyll is a strictly light-dependent multistep process in higher plants. The light-dependent step is catalysed by NADPH:protochlorophyllide oxidoreductase (POR, EC.1.6.99.1), which reduces protochlorophyllide (Pchlide) to chlorophyllide (Chlide). POR is nucleus-encoded and post-translationally imported into plastids. It has been proposed that the import of a POR protein isozyme (PORA) is totally dependent on Pchlide and uses a novel import pathway. This proposal is based on findings that PORA import only occurs in the presence of Pchlide and that the presence of overexpressed precursor of Rubisco small subunit (pSS), a protein which is known to use the general import pathway, does not outcompete PORA import. Another study demonstrated that POR precursor protein (pPOR) can be cross-linked to one of the components in the translocation machinery, Toc75, in the absence of Pchlide, and that its import can be outcompeted by the addition of the pSS. This indicates that pSS and pPOR may use the same translocation mechanism. Thus, POR does not necessarily need Pchlide for import – which is in contrast to earlier observations – and the exact POR import mechanism remains unresolved. Once in the stroma, the POR transit peptide is cleaved off and the mature POR protein is associated to the plastid inner membranes. Formation of the correct membrane–associated, thermolysin-protected assembly is strictly dependent of NADPH. As a final step, the formation of the NADPH-Pchlide-POR complex occurs. When POR accumulates in the membranes of proplastids, an attraction of monogalactosyl diacylglycerol (MGDG) can occur, leading to the formation of prolamellar bodies (PLBs) and the development of etioplasts in darkness.

Place, publisher, year, edition, pages
Berlin: Springer-Verlag, 2003
Keywords
chlorophyll biosynthesis, chloroplasts, membrane assembly, protein translocation
National Category
Biological Sciences
Identifiers
urn:nbn:se:hh:diva-419 (URN)10.1023/A:1020795415631 (DOI)000178667200001 ()2-s2.0-0037275907 (Scopus ID)2082/757 (Local ID)2082/757 (Archive number)2082/757 (OAI)
Available from: 2007-01-23 Created: 2007-01-23 Last updated: 2018-03-23Bibliographically approved
Dahlin, C. (2003). Surface charge densities and membrane fluidities in thylakoids with different degrees of thylakoid appression after Norflurazon treatment. Photosynthetica (Praha), 41(4), 635-639
Open this publication in new window or tab >>Surface charge densities and membrane fluidities in thylakoids with different degrees of thylakoid appression after Norflurazon treatment
2003 (English)In: Photosynthetica (Praha), ISSN 0300-3604, E-ISSN 1573-9058, Vol. 41, no 4, p. 635-639Article in journal (Refereed) Published
Abstract [en]

Wheat seedlings (Triticum aestivum L.) develop plastids (etioplasts and chloroplasts) which exhibit alterations in inner membrane organisation after treatment with Norflurazon (NF), an inhibitor of carotenoid biosynthesis. In dark-grown plants, results in a decreased amount of partitions (contact zones) between prothylakoids. In weak red light, the results in plants containing chloroplasts devoid of grana.

Assays have been performed to investigate the membrane surface charge density in these membranes, and relate possible differences to the absence of (pro-)thylakoid overlap after NF teatment. Using the fluorescent probe 9- amino acridine (9-AA), the average surface charge density of isolated PTs was -21.8±3.2 mC m-2 and - 27.4±2.6 mC m-2 in the control and after, respectively. Thylakoid membranes isolated from plants grown in weak red light exhibited slightly more negative values, -23.5±2.9 mC m-2 and -29.0±2.1 mC m-2, in control and after, respectively. The surface charge density of destacked thylakoids from greenhouse-grown untreated plants, containing extensive grana stacking, was -34.3±2.5 mC m-2. Assays using the fluorescent probe of DPH (1,6- diphenyl- 1,3,5- hexatriene) showed that this probe exhibits a higher polarisation value when incorporated into thylakoids from NF- treated plants compared to untreated plants grown in weak red light. The highest polarisation value was found in untreated plants grown in the greenhouse. This indicates a lower rotation transition of the probe in the lipid environment of thylakoids after NF treatment, which can be interpreted as more rigid membranes. These results suggest that the surface charge density and the mobility of membrane components may play a major role for the formation of partitions in dark-grown plants and in the formation of grana in plants grown in weak red light.

23 Additional key words: chloroplasts; etioplasts; (pro-)thylakoids; Triticum; stacking;

wheat; 9- amino acridine.

Place, publisher, year, edition, pages
Springer-Verlag, 2003
Keywords
chloroplast, etioplast, thylakoids, 9-amino acridine, (Pro-)thylakoids, Stacking, Triticum, Wheat
National Category
Natural Sciences
Identifiers
urn:nbn:se:hh:diva-2034 (URN)10.1023/B:PHOT.0000027532.55335.a7 (DOI)000221306100022 ()2-s2.0-3542996369 (Scopus ID)2082/2429 (Local ID)2082/2429 (Archive number)2082/2429 (OAI)
Available from: 2008-10-10 Created: 2008-10-10 Last updated: 2018-03-23Bibliographically approved
Engdahl, S., Aronsson, H., Sundqvist, C., Timko, M. P. & Dahlin, C. (2001). Association of the NADPH: protochlorophyllide oxidoreductase (POR) with isolated etioplast inner membranes from wheat. The Plant Journal, 27(4), 297-304
Open this publication in new window or tab >>Association of the NADPH: protochlorophyllide oxidoreductase (POR) with isolated etioplast inner membranes from wheat
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2001 (English)In: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 27, no 4, p. 297-304Article in journal (Refereed) Published
Abstract [en]

Membrane association of NADPH:protochlorophyllide oxidoreductase (POR, EC: 1.6.99.1) with isolated prolamellar bodies (PLBs) and prothylakoids (PTs) from wheat etioplasts was investigated. in vitro-expressed radiolabelled POR, with or without transit peptide, was used to characterize membrane association conditions. Proper association of POR with PLBs and PTs did not require the presequence, whereas NADPH and hydrolysable ATP were vital for the process. After treating the membranes with thermolysin, sodium hydroxide or carbonate, a firm attachment of the POR protein to the membrane was found. Although the PLBs and PTs differ significantly in their relative amount of POR in vivo, no major differences in POR association capacity could be observed between the two membrane systems when exogenous NADPH was added, Experiments run with only an endogenous NADPH source almost abolished association of POR with both PLBs and PTs. In addition, POR protein carrying a mutation in the putative nucleotide-binding site (ALA06) was unable to bind to the inner membranes in the presence of NADPH, which further demonstrates that the co-factor is essential for proper membrane association. POR protein carrying a mutation in the substrate-binding site (ALA24) showed less binding to the membranes as compared to the wild type. The results presented here introduce studies of a novel area of protein-membrane interaction, namely the association of proteins with a paracrystalline membrane structure, the PLB.

Place, publisher, year, edition, pages
Oxford: Blackwell, 2001
National Category
Botany
Identifiers
urn:nbn:se:hh:diva-3381 (URN)10.1046/j.1365-313x.2001.01094.x (DOI)000170799100003 ()11532175 (PubMedID)2-s2.0-0034870647 (Scopus ID)
Available from: 2010-02-25 Created: 2009-12-01 Last updated: 2018-03-23Bibliographically approved
Aronsson, H., Sundqvist, C., Timko, M. P. & Dahlin, C. (2001). Characterisation of the assembly pathway of the pea NADPH:protochlorophyllide (Pchlide) oxidoreductase (POR), with emphasis on the role of its substrate, Pchlide. Physiologia Plantarum: An International Journal for Plant Biology, 111(2), 239-244
Open this publication in new window or tab >>Characterisation of the assembly pathway of the pea NADPH:protochlorophyllide (Pchlide) oxidoreductase (POR), with emphasis on the role of its substrate, Pchlide
2001 (English)In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 111, no 2, p. 239-244Article in journal (Refereed) Published
Abstract [en]

The homologous import and membrane association of a key enzyme for chlorophyll biosynthesis, the NADPH:protochlorophyllide (Pchlide) oxidoreductase (PAR, EC 1.6.99.1) into pea chloroplasts was investigated in vitro. The co-factor, NADPH, decreased binding of the precursor protein (pPOR) to the envelope membranes in the presence of ATP. The decrease of the binding reaction with NADPH was not observed with the precursor of the small subunit of Rubisco (pSS). To investigate possible substrate-dependency for the import reaction, internal Pchlide concentrations in the plastids were raised by either an addition of ÎŽ-aminolevulinic acid to isolated plastids or etiolation of the seedlings prior to plastid isolation. Increased amounts of plastid-bound Pchlide gave no observable differences in POR import. The capacity of POR and 11 different POR mutants, carrying charged-to-alanine scanning substitutions, to form a catalytically active POR-Pchlide-NADPH complex and to associate with the thylakoid membranes in a protease-resistant way were tested. Wild-type POR, as well as the mutants with charge substitutions in the N-terminal region of the protein, exhibited higher catalytic activity than the POR mutants carrying substitutions in the C-terminal region. Formation of a catalytically active complex did not, however, increase the association efficiency onto the thylakoids. We can, therefore, postulate that the import of pea POR into pea chloroplasts was not substrate-dependent, nor did formation of catalytically active complexes stimulate or inhibit the membrane association reaction of POR.

Place, publisher, year, edition, pages
Hoboken, NJ: Wiley-Blackwell Publishing Inc., 2001
Keywords
alanine, amino acid substitution, amino terminal sequence, aminolevulinic acid, biochemical pathway, chloroplast, envelope protein, enzyme activity, enzyme subunit, in vitro culture, NADPH:protochlorophyllide oxidoreductase, pea, protein binding, ribulosebisphosphate carboxylase, wild relative
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:hh:diva-37631 (URN)10.1034/j.1399-3054.2001.1110216.x (DOI)000166780300016 ()2-s2.0-0034772456 (Scopus ID)
Note

Funding: Adlerbertska Foundation, the Hierta-Retzius Foundation (H. A.), the Carl Trygger Foundation for Scientific Research (C. D.), the Swedish Natural Science Research Council (C. S.) and the US Department of Energy(M. P. T.)

Available from: 2018-07-20 Created: 2018-07-20 Last updated: 2018-07-20Bibliographically approved
Aronsson, H., Almqvist, J., Sundqvist, C., Timko, M. & Dahlin, C. (1998). Characterization of the plastid import reaction of the pea NADPH-protochlorophyllide oxidoreductase (POR). In: Joan H. Argyroudi-Akoyunoglou, Horst Senger (Ed.), Joan H. Argyroudi-Akoyunoglou, Horst Senger (Ed.), The Chloroplast: From Molecular Biology to Biotechnology. Paper presented at NATO Advanced Research Workshop on The Chloroplast: From Molecular Biology to Biotechnology Kolymbari-Chania, Crete, Greece 10-15 August 1998 (pp. 167-170). New York: Springer-Verlag
Open this publication in new window or tab >>Characterization of the plastid import reaction of the pea NADPH-protochlorophyllide oxidoreductase (POR)
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1998 (English)In: The Chloroplast: From Molecular Biology to Biotechnology / [ed] Joan H. Argyroudi-Akoyunoglou, Horst Senger, New York: Springer-Verlag , 1998, p. 167-170Conference paper, Published paper (Refereed)
Abstract [en]

NADPH: protochlorophyllide (POR) is a vital enzyme in the biosynthesis of chlorophyl where it catalyzes the reduction of Pchlide into Chlide in a light-dependent manner. POR is nucleus-encoded and imported into the plastids where it is found at the inner membranes. Together with its substrate and the co-factor NADPH it forms a ternary complex which is needed for catalytical activity. The anomaly of a decreasing POR level during active chlorophyll synthesis was cleared with the discovery of two different POR proteins, POR-A and POR-B, in barley and Arabidopsis thaliana. During greening, POR-A is negatively regulated by light both at transcriptional and proteolytical levels. In addition, the import of POR-A, but not POR-B, has been suggestedto require Pchlide in order to be translocated into the plastid. In this respect, POR-A differs from other known nucleus-encoded plastid proteins, and as it appears, this requirements represents a novel and exclusive import characteristic. In pea, only one POR gene has been found indicating that the situation for the regulation of POR import and accumulation is far from clear. We here present a characterization of the import conditions of the pea POR, including the potentional role of Pchlide inthe translocation step.

Place, publisher, year, edition, pages
New York: Springer-Verlag, 1998
National Category
Natural Sciences
Identifiers
urn:nbn:se:hh:diva-3917 (URN)9780792355779 (ISBN)0792355776 (ISBN)
Conference
NATO Advanced Research Workshop on The Chloroplast: From Molecular Biology to Biotechnology Kolymbari-Chania, Crete, Greece 10-15 August 1998
Available from: 2010-02-23 Created: 2010-02-23 Last updated: 2018-03-23Bibliographically approved
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