| 1. |
- Flores-Perez, U., et al.
(författare)
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Functional Analysis of the Hsp93/ClpC Chaperone at the Chloroplast Envelope
- 2016
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 170:1, s. 147-162
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Tidskriftsartikel (refereegranskat)abstract
- The Hsp100-type chaperone Hsp93/ClpC has crucial roles in chloroplast biogenesis. In addition to its role in proteolysis in the stroma, biochemical and genetic evidence led to the hypothesis that this chaperone collaborates with the inner envelope TIC complex to power preprotein import. Recently, it was suggested that Hsp93, working together with the Clp proteolytic core, can confer a protein quality control mechanism at the envelope. Thus, the role of envelope-localized Hsp93, and the mechanism by which it participates in protein import, remain unclear. To analyze the function of Hsp93 in protein import independently of its ClpP association, we created a mutant of Hsp93 affecting its ClpP-binding motif (PBM) (Hsp93[P-]), which is essential for the chaperone's interaction with the Clp proteolytic core. The Hsp93[P-] construct was ineffective at complementing the pale-yellow phenotype of hsp93 Arabidopsis (Arabidopsis thaliana) mutants, indicating that the PBM is essential for Hsp93 function. As expected, the PBM mutation negatively affected the degradation activity of the stromal Clp protease. The mutation also disrupted association of Hsp93 with the Clp proteolytic core at the envelope, without affecting the envelope localization of Hsp93 itself or its association with the TIC machinery, which we demonstrate to be mediated by a direct interaction with Tic110. Nonetheless, Hsp93[P-] expression did not detectably improve the protein import efficiency of hsp93 mutant chloroplasts. Thus, our results do not support the proposed function of Hsp93 in protein import propulsion, but are more consistent with the notion of Hsp93 performing a quality control role at the point of import.
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| 2. |
- Johansson, Oskar N., 1984, et al.
(författare)
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Friends With Benefits: Exploring the Phycosphere of the Marine Diatom Skeletonema marinoi
- 2019
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Marine diatoms are the dominant phytoplankton in the temperate oceans and coastal regions, contributing to global photosynthesis, biogeochemical cycling of key nutrients and minerals and aquatic food chains. Integral to the success of marine diatoms is a diverse array of bacterial species that closely interact within the diffusive boundary layer, or phycosphere, surrounding the diatom partner. Recently, we isolated seven distinct bacterial species from cultures of Skeletonema marinoi, a chain-forming, centric diatom that dominates the coastal regions of the temperate oceans. Genomes of all seven bacteria were sequenced revealing many unusual characteristics such as the existence of numerous plasmids of widely varying sizes. Here we have investigated the characteristics of the bacterial interactions with S. marinoi, demonstrating that several strains (Arenibacter algicola strain SMS7, Marinobacter salarius strain SMRS, Sphingorhabdus flavimaris strain SMR4y, Sulfitobacter pseudonitzschiae strain SMR1, Yoonia vestfoldensis strain SMR4r and Roseovarius mucosus strain SMR3) stimulate growth of the diatom partner. Testing of many different environmental factors including low iron concentration, high and low temperatures, and chemical signals showed variable effects on this growth enhancement by each bacterial species, with the most significant being light quality in which green and blue but not red light enhanced the stimulatory effect on S. marinoi growth by all bacteria. Several of the bacteria also inhibited growth of one or more of the other bacterial strains to different extents when mixed together. This study highlights the complex interactions between diatoms and their associated bacteria within the phycosphere, and that further studies are needed to resolve the underlying mechanisms for these relationships and how they might influence the global success of marine diatoms.
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| 3. |
- Johansson, Oskar N., 1984, et al.
(författare)
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Phenomics reveals a novel putative chloroplast fatty acid transporter in the marine diatom Skeletonema marinoi involved in temperature acclimation
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Diatoms are the dominant phytoplankton in temperate oceans and coastal regions and yet little is known about the genetic basis underpinning their global success. Here, we address this challenge by developing the first phenomic approach for a diatom, screening a collection of randomly mutagenized but identifiably tagged transformants. Based upon their tolerance to temperature extremes, several compromised mutants were identified revealing genes either stress related or encoding hypothetical proteins of unknown function. We reveal one of these hypothetical proteins is a novel putative chloroplast fatty acid transporter whose loss affects several fatty acids including the two omega-3, long-chain polyunsaturated fatty acids - eicosapentaenoic and docosahexaenoic acid, both of which have medical importance as dietary supplements and industrial significance in aquaculture and biofuels. This mutant phenotype not only provides new insights into the fatty acid biosynthetic pathways in diatoms but also highlights the future value of phenomics for revealing specific gene functions in these ecologically important phytoplankton.
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| 4. |
- Johansson, Oskar N., 1984, et al.
(författare)
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Skeletonema marinoi as a new genetic model for marine chain-forming diatoms
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Diatoms are ubiquitous primary producers in marine ecosystems and freshwater habitats. Due to their complex evolutionary history, much remains unknown about the specific gene functions in diatoms that underlie their broad ecological success. In this study, we have genetically transformed the centric diatom Skeletonema marinoi, a dominant phytoplankton species in temperate coastal regions. Transformation of S. marinoi is the first for a true chain-forming diatom, with the random genomic integration via non homologous recombination of a linear DNA construct expressing the resistance gene to the antibiotic zeocin. A set of molecular tools were developed for reliably identifying the genomic insertion site within each transformant, many of which disrupt recognizable genes and constitute null or knock-down mutations. We now propose S. marinoi as a new genetic model for marine diatoms, representing true chain-forming species that play a central role in global photosynthetic carbon sequestration and the biogeochemical cycling of silicates and various nutrients, as well as having potential biotechnological applications.
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| 5. |
- Karlsson, Max, et al.
(författare)
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Phenotypic and genotypic adaptations in a riverine green alga (Chlorophyceae, Selenastraceae) as a response to long-term exposure to chemical stress
- 2019
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Ingår i: SETAC Helsinki - SETAC Europe 29th Annual Meeting, 26 - 30 May 2019, Helsinki, Finland.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Herbicide pollution is a common problem in agricultural streams due to their extensive use and their unwanted effects on non-target species inhabiting these systems. Selanastraceae is a family of green algae that are particularly dominant in freshwater, making them a key component in the base of the food chain and an important part of the oxygen production. Therefore, it is crucial from a conservation point of view to accurately monitor the ecotoxicological impact of herbicides on this group of algae, not only on a short-term scale (e.g. days or weeks), but also in a long-term perspective (e.g. months and years). In this work, phenotypic and genotypic differences are studied between different strains of a population of Kirchneriella (Chlorophyceae, Selenastraceae) isolated from a stream polluted by herbicides over a 20-year period (Skivarpsån, SE Sweden). According to mixture toxicity modelling performed on data obtained from the Swedish pesticide monitoring program, the main drivers of algal toxicity in this river are the herbicides diflufenican (carotenoid synthesis inhibitor) and isoproturon (PSII inhibitor). Three strains of the isolated algae are examined in this study: two strains from the field that have been exposed to different levels of herbicides and one laboratory strain that has never been exposed to herbicide pollution. The taxonomy of this algae is investigated by light microscopy and DNA barcoding analyses (chloroplast 23S rRNA gene). Phenotypic differences between the strains are examined as impacts on growth rate, cell size, photosynthetic activity (chl fluorescence measurements), pigment content and sensitivity to the specific herbicides mentioned earlier (EC50s). Genotypic differences are studied as single nucleotide polymorphisms thought to be induced through exposure to diflufenican and isoproturon on pds and psbA genes via PCR amplification, cloning and sequencing. The results obtained from this project will contribute to a better understanding of genetic and phenotypic adaptations in green algae as a response to herbicide pollution (evolutionary toxicology) and their implications for ecological functions.
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| 6. |
- Mikhailov, V. A., et al.
(författare)
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Dual stoichiometry and subunit organization in the ClpP1/P2 protease from the cyanobacterium Synechococcus elongatus
- 2015
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Ingår i: Journal of Structural Biology. - : Elsevier BV. - 1047-8477. ; 192:3, s. 519-527
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Tidskriftsartikel (refereegranskat)abstract
- The Clp protease is conserved among eubacteria and most eukaryotes, and uses ATP to drive protein substrate unfolding and translocation into a chamber of sequestered proteolytic active sites. To investigate the proteolytic core of the ClpXP1/P2 protease from the cyanobacterium Synechococcus elongatus we have used a non-denaturing mass spectrometry approach. We show that the proteolytic core is a double ring tetradecamer consisting of an equal number of ClpP1 and ClpP2 subunits with masses of 21.70 and 23.44 kDa, respectively. Two stoichiometries are revealed for the heptameric rings: 4ClpP1 + 3ClpP2 and 3ClpP1 + 4ClpP2. When combined in the double ring the stoichiometries are (4ClpP1 + 3ClpP2) + (3ClpP1 + 4ClpP2) and 2 x (3ClpP1 + 4ClpP2) with a low population of a 2 x (4ClpP1 + 3ClpP2) tetradecamer. The assignment of the stoichiometries is confirmed by collision-induced dissociation of selected charge states of the intact heptamer and tetradecamer. Presence of the heterodimers, heterotetramers and heterohexamers, and absence of the mono-oligomers, in the mass spectra of the partially denatured protease indicates that the ring complex consists of a chain of ClpP1/ClpP2 heterodimers with the ring completed by an additional ClpP1 or ClpP2 subunit. (C) 2015 The Authors. Published by Elsevier Inc.
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| 7. |
- Pinder, Matthew I. M., 1990, et al.
(författare)
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Genome Sequence of Kordia sp. Strain SMS9 Identified in a Non-Axenic Culture of the Diatom Skeletonema marinoi.
- 2019
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Ingår i: Journal of genomics. - : Ivyspring International Publisher. - 1839-9940. ; 7, s. 46-49
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Tidskriftsartikel (refereegranskat)abstract
- Initial efforts to sequence the genome of the marine diatom Skeletonema marinoi were hampered by the presence of genetic material from bacteria, and there was sufficient material from some of these bacteria to enable the assembly of full chromosomes. Here, we report the genome of strain SMS9, one such bacterial species identified in a non-axenic culture of S. marinoi strain ST54. Its 5,482,391 bp circular chromosome contains 4,641 CDSs, and has a G+C content of 35.6%. Based on 16S rRNA comparison, phylotaxonomic analysis, and the genome similarity metrics dDDH and OrthoANI, we place this strain in the genus Kordia, and to the best of our knowledge, this is the first Kordia species to be initially described from European waters. As attempts to culture this strain have failed, however, the specifics of its relationship with S. marinoi are still uncertain.
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| 8. |
- Tryggvesson, Anders, 1975, et al.
(författare)
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Characterization of ClpS2, an essential adaptor protein for the cyanobacterium Synechococcus elongatus
- 2015
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Ingår i: Febs Letters. - : Wiley. - 0014-5793. ; 589:24, s. 4039-4046
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Tidskriftsartikel (refereegranskat)abstract
- The adaptor protein ClpS associates to the Clp protease and promotes degradation of N-end rule substrates in eubacteria and in algal/plant chloroplasts. Cyanobacteria are unusual in having two distinct ClpS paralogs. Although ClpS1 is typical of bacterial ClpS, ClpS2 differs in crucial ways. ClpS2 in Synechococcus elongatus is a relatively low- abundant, soluble protein essential for phototrophic growth. Like ClpS1, ClpS2 binds to the ClpCP3/R protease to block alpha-casein degradation and promote that of N-end rule substrates in vitro. However, their substrate specificity differs, with ClpS1 recognizing destabilizing Phe and Tyr residues at the substrate N-terminus whereas ClpS2 recognizes Leu. Overall, ClpS2 appears to have independently evolved in cyanobacteria to degrade a particular group of proteins, whose turnover is vital for cell viability. (C) 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
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| 9. |
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| 10. |
- Töpel, Mats H., 1973, et al.
(författare)
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Complete Genome Sequence of Novel Sulfitobacter pseudonitzschiae Strain SMR1, Isolated from a Culture of the Marine Diatom Skeletonema marinoi.
- 2019
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Ingår i: Journal of Genomics. - : Ivyspring International Publisher. - 1839-9940. ; 7, s. 7-10
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Tidskriftsartikel (refereegranskat)abstract
- When studying diatoms, an important consideration is the role of associated bacteria in the diatom-microbiome holobiont. To that end, bacteria isolated from a culture of Skeletonema marinoi strain R05AC were sequenced, one of which being bacterial strain SMR1, presented here. The genome consists of a circular chromosome and seven circular plasmids, totalling 5,121,602 bp. After phylotaxonomic analysis and 16S rRNA sequence comparison, we place this strain in the taxon Sulfitobacter pseudonitzschiae on account of similarity to the type strain. The annotated genome suggests similar interactions between strain SMR1 and its host diatom as have been shown previously in diatom-associated Sulfitobacter, for example bacterial production of growth hormone for its host, and breakdown of diatom-derived DMSP by Sulfitobacter for use as a sulfur source.
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