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1.	Andersson, Mats X., 1977, et al. (författare) Involvement of the Electrophilic Isothiocyanate Sulforaphane in Arabidopsis Local Defense Responses 2015 Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 167:1 Tidskriftsartikel (refereegranskat)abstract Plants defend themselves against microbial pathogens through a range of highly sophisticated and integrated molecular systems. Recognition of pathogen-secreted effector proteins often triggers the hypersensitive response (HR), a complex multicellular defense reaction where programmed cell death of cells surrounding the primary site of infection is a prominent feature. Even though the HR was described almost a century ago, cell-to-cell factors acting at the local level generating the full defense reaction have remained obscure. In this study, we sought to identify diffusible molecules produced during the HR that could induce cell death in naive tissue. We found that 4-methylsulfinylbutyl isothiocyanate (sulforaphane) is released by Arabidopsis (Arabidopsis thaliana) leaf tissue undergoing the HR and that this compound induces cell death as well as primes defense in naive tissue. Two different mutants impaired in the pathogen-induced accumulation of sulforaphane displayed attenuated programmed cell death upon bacterial and oomycete effector recognition as well as decreased resistance to several isolates of the plant pathogen Hyaloperonospora arabidopsidis. Treatment with sulforaphane provided protection against a virulent H. arabidopsidis isolate. Glucosinolate breakdown products are recognized as antifeeding compounds toward insects and recently also as intracellular signaling and bacteriostatic molecules in Arabidopsis. The data presented here indicate that these compounds also trigger local defense responses in Arabidopsis tissue.
2.	Andersson, Mats X., 1977, et al. (författare) Oxylipin profiling of the hypersensitive response in Arabidopsis thaliana - Formation of a novel oxo-phytodienoic acid-containing galactolipid, arabidopside E 2006 Ingår i: JOURNAL OF BIOLOGICAL CHEMISTRY. - 0021-9258. ; 281:42, s. 31528-31537 Tidskriftsartikel (refereegranskat)abstract Oxidation products of unsaturated fatty acids, collectively known as oxylipins, function as signaling molecules in plants during development, wounding, and insect and pathogen attack. Certain oxylipins are also known to have direct cytotoxic effects on pathogens. We used inducible expression of bacterial avirulence proteins in planta to study the involvement of oxylipins in race-specific defense against bacterial pathogens. We demonstrate that recognition of the Pseudomonas syringae avirulence protein AvrRpm1 induces 9- and 13-lipoxygenase-dependent oxylipin synthesis in Arabidopsis thaliana. The major oxylipins accumulated were jasmonic acid, 12-oxo-phytodienoic acid, and dinor-oxo-phytodienoic acid. The majority of the newly formed oxylipins (> 90%) was found to be esterified to glycerolipids, whereby 12-oxo-phytodienoic acid and dinor-oxo-phytodienoic acid were found to be esterified to a novel galactolipid. The structure of the substance was determined as a monogalactosyldiacylglycerol containing two 12-oxo-phytodienoic acids and one dinor-oxo-phytodienoic acid acyl chain and was given the trivial name arabidopside E. This substance accumulated to surprisingly high levels, 7 - 8% of total lipid content, and was shown to inhibit growth of a bacterial pathogen in vitro. Arabidopside E was formed also after recognition of the avirulence protein AvrRpt2, suggesting that this could be a conserved feature of defense reactions against bacterial pathogens. In conclusion, the data presented suggest a role of enzymatically formed oxylipins, especially the octadecanoids and arabidopside E in race-specific resistance against bacterial pathogens.
3.	Björk, Robert G., 1974, et al. (författare) Contrasting effects of wood ash application on microbial community structure, biomass and processes in drained forested peatlands 2010 Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 73:3, s. 550-562 Tidskriftsartikel (refereegranskat)abstract The effects of wood ash application on soil microbial processes were investigated in three drained forested peatlands, which differed in nutrient status and time since application. Measured variables included concentrations of soil elements and phospholipid fatty acids (PLFAs), net nitrogen mineralisation, nitrification and denitrification enzyme activity, potential methane oxidation, methane production and microbial respiration kinetics. Wood ash application had a considerable influence on soil element concentrations. This mirrored a decrease in the majority of the microbial biomarkers by more than one-third in the two oligotrophic peatlands, although microbial community composition was not altered. The decreases in PLFAs coincided with reduced net ammonification and net nitrogen mineralisation. Other measured variables did not change systematically as a result of wood ash application. No significant changes in microbial biomass or processes were found in the mesotrophic peatland, possibly because too little time (1 year) had elapsed since the wood ash application. This study suggests that oligotrophic peatlands can be substantially affected by wood ash for a period of at least four years after application. However, within 25 years of the wood ash application, the microbial biomass seemed to have recovered or adapted to enhanced element concentrations in the soil.
4.	Nilsson, Anders K., 1982, et al. (författare) Acylated monogalactosyl diacylglycerol : prevalence in the plant kingdom and identification of an enzyme catalyzing galactolipid head group acylation in Arabidopsis thaliana 2015 Ingår i: The Plant Journal. - : Wiley-Blackwell. - 0960-7412 .- 1365-313X. ; 84:6, s. 1152-1166 Tidskriftsartikel (refereegranskat)abstract The lipid phase of the thylakoid membrane is mainly composed of the galactolipids mono-and digalactosyl diacylglycerol (MGDG and DGDG, respectively). It has been known since the late 1960s that MGDG can be acylated with a third fatty acid to the galactose head group (acyl-MGDG) in plant leaf homogenates. In certain brassicaceous plants like Arabidopsis thaliana, the acyl-MGDG frequently incorporates oxidized fatty acids in the form of the jasmonic acid precursor 12-oxo-phytodienoic acid (OPDA). In the present study we further investigated the distribution of acylated and OPDA-containing galactolipids in the plant kingdom. While acyl-MGDG was found to be ubiquitous in green tissue of plants ranging from non-vascular plants to angiosperms, OPDA-containing galactolipids were only present in plants from a few genera. A candidate protein responsible for the acyl transfer was identified in Avena sativa (oat) leaf tissue using biochemical fractionation and proteomics. Knockout of the orthologous gene in A. thaliana resulted in an almost total elimination of the ability to form both non-oxidized and OPDA-containing acyl-MGDG. In addition, heterologous expression of the A. thaliana gene in E. coli demonstrated that the protein catalyzed acylation of MGDG. We thus demonstrate that a phylogenetically conserved enzyme is responsible for the accumulation of acyl-MGDG in A. thaliana. The activity of this enzyme in vivo is strongly enhanced by freezing damage and the hypersensitive response.
5.	Andersson, Mats X., 1977, et al. (författare) Phospholipase-dependent signalling during the AvrRpm1- and AvrRpt2-induced disease resistance responses in Arabidopsis thaliana 2006 Ingår i: Plant Journal. - 0960-7412. ; 47:6, s. 947-959 Tidskriftsartikel (refereegranskat)abstract Bacterial pathogens deliver type III effector proteins into plant cells during infection. On susceptible host plants, type III effectors contribute to virulence, but on resistant hosts they betray the pathogen to the plant's immune system and are functionally termed avirulence (Avr) proteins. Recognition induces a complex suite of cellular and molecular events comprising the plant's inducible defence response. As recognition of type III effector proteins occurs inside host cells, defence responses can be elicited by in planta expression of bacterial type III effectors. We demonstrate that recognition of either of two type III effectors, AvrRpm1 or AvrRpt2 from Pseudomonas syringae, induced biphasic accumulation of phosphatidic acid (PA). The first wave of PA accumulation correlated with disappearance of monophosphatidylinosotol (PIP) and is thus tentatively attributed to activation of a PIP specific phospholipase C (PLC) in concert with diacylglycerol kinase (DAGK) activity. Subsequent activation of phospholipase D (PLD) produced large amounts of PA from structural phospholipids. This later wave of PA accumulation was several orders of magnitude higher than the PLC-dependent first wave. Inhibition of phospholipases blocked the response, and feeding PA directly to leaf tissue caused cell death and defence-gene activation. Inhibitor studies ordered these events relative to other known signalling events during the plant defence response. Influx of extracellular Ca2+ occurred downstream of PIP-degradation, but upstream of PLD activation. Production of reactive oxygen species occurred downstream of the phospholipases. The data presented indicate that PA is a positive regulator of RPM1- or RPS2-mediated disease resistance signalling, and that the biphasic PA production may be a conserved feature of signalling induced by the coiled-coil nucleotide binding domain leucine-rich repeat class of resistance proteins.
6.	Björk, Robert G., 1974, et al. (författare) Temporal pattern of CO2, CH4 and N2O fluxes and soil microbial structure from snow-covered Alpine plant communities 2006 Ingår i: Abstracts and Proceedings of the Geological Society of Norway. ; :4 Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Global warming is expected to have large effects on carbon exchange between the biosphere and the atmosphere in the Arctic. Arctic ecosystems, which can be a net sink in the summer, are often a net source of CO2 to the atmosphere on an annual basis. Few studies on winter CO2 and CH4 efflux have been conducted in the subarctic part of Sweden. So far, no integrated estimates of winter fluxes of CO2, CH4 or N2O has been reported from the alpine areas in the Scandinavian mountains. As much as 44 to 53% of the northern hemispheres landmass may be snow covered for parts of the year. The depth and spatial spread of snow cover is a result of moisture availability, duration of temperatures bellow 0ºC, storm frequency and the more local factors such as wind redistribution and compaction. In future climate scenarios, predictions of warmer climate and increased precipitations are often mentioned, but to which extent is more uncertain. However, the major changes in precipitation will occur over the North Pacific, North Atlantic and Scandinavia. The controlling factor for microbial activity in the organic layer during winter in alpine areas is the development of a consistent snow cover, which effectively decouples the soil from the atmospheric temperature. The air and soil temperature the days before snow cover development is important, as it sets the temperature conditions for the whole winter period. Soil microbial activity is markedly reduced below temperatures of 0 to -5°C, when the soil starts to freeze and free water becomes limited. Nitrogen mineralisation, nitrification and denitrification can, however, be maintained down to -4°C, and N2O production (from denitrification) in frozen soils has potential to affect annual dynamics and budgets of N (although the soil pore water content prior to freezing is an important regulating factor for winter N2O production). Snowbed communities are rarely, if ever, subjected to temperatures as low as -5°C, which implies that they may be favourable for microbial activity during the winter. Furthermore, tundra soil microbial biomass reaches its annual peak under snow, and fungi account for most of the biomass. However, how the microbial community changes during winter and snowmelt are poorly know and, in particular, in relation to trace gas fluxes. Flux of CO2, CH4 and N2O through a seasonal snowpack, using Fick’s law, from four plant communities with different snow regime and how it changes during snowmelt in the subarctic-alpine part of Sweden will be presented. We will also try to relate the trace gas fluxes to the soil microbial community composition using phospholipid fatty acid analysis.
7.	Björk, Robert G., 1974, et al. (författare) Temporal variation in soil microbial communities and the influence of snow cover 2007 Ingår i: The 14th ITEX workshop, Falls Creek, Victoria, Australia, 2–6 February 2007.. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Global climate change is projected to have a large impact in arctic and alpine areas. Future projections with increased temperature also include increased precipitation, but to which extent is uncertain. However, the major changes in precipitation will occur over the North Pacific, North Atlantic and Scandinavia. As much as 44 to 53% of the northern hemispheres landmass may be snow covered for parts of the year and in higher alpine terrain the increased precipitation will lead to a greater snow accumulation. The controlling factor for microbial activity in the organic layer during winter in alpine areas is the development of a consistent snow cover, which effectively decouples the soil from the atmospheric temperature. The air and soil temperature the days before snow cover development is important, as it sets the temperature conditions for the whole winter period. Soil microbial activity is markedly reduced below temperatures of 0 to -5°C, when the soil starts to freeze and free water becomes limited. Nitrogen mineralisation, nitrification and denitrification can, however, be maintained down to -4°C, and N2O production (from denitrification) in frozen soils could potentially affect the annual dynamics and budgets of N. Snowbed communities are rarely, if ever, subjected to temperatures as low as -5°C, which implies that they may be favourable for microbial activity during the winter. Furthermore, tundra soil microbial biomass reaches its annual peak under snow, and fungi account for most of the biomass. However, how the microbial community changes during winter and snowmelt is poorly known and, in particular, in relation to trace gas fluxes. The objective of our study was, therefore, to investigate the temporal pattern of soil microbial structure in four plant communities with contrasting snow cover and nitrogen turnover. This study was conducted at Latnjajaure Field Station (LFS) located in the midalpine region in northern Sweden. The study includes four different plant communities, heath snowbed, heath meadow, meadow snowbed, and mesic meadow. To characterize the soil microbial community we used phospholipid fatty acid analysis (PLFA), which is a method targeting the fatty acid profiles of membrane phospholipids microorganisms. The results show that at each individual sampling occasion the four plant communities’ exhibits different soil microbial structure. However, the temporal variation is larger than the difference across plant communities. This temporal shift in microbial structure seems to be partially related to the fatty acid 18:2ω6, indicative of fungi, which show a high proportion in soils protected by snow and decreases after snow melt. Furthermore, the shift in microbial structure during the season is more modest in snowbeds than the mesic heath and meadow.
8.	Björk, Robert G., 1974, et al. (författare) Temporal variation in soil microbial communities in Alpine tundra 2008 Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 40:1, s. 266-268 Tidskriftsartikel (refereegranskat)abstract Temporal variation in soil microbial communities was studied at a mid-alpine environment in Latnjajaure, northern Sweden, using phospholipid fatty acid (PLFA) analysis. The results show two seasonal shifts in microbial composition. The first shift was associated with snowmelt and mainly related to a decrease in fungal PLFAs, accompanied by an increase in branched 17:0 and methylated PLFAs (biomarkers for Gram-positive- and actinobacteria, respectively), resulting in a decrease in the ratio of fungi-to-bacteria. The second shift occurred across the growing, season, and was associated with a switch from shorter to longer PLFAs and an increase in 18:1 omega 7 (biomarker for Gram-negative bacteria). Vegetation, snow cover dynamics, and N turnover seem to be of minor importance to broadscale microbial community structure in this area. (c) 2007 Elsevier Ltd. All rights reserved.
9.	Cheregi, Otilia, et al. (författare) Transcriptome analysis reveals insights into adaptive responses of two marine microalgae species to Nordic seasons 2023 Ingår i: Algal Research. - 2211-9264. ; 74 Tidskriftsartikel (refereegranskat)abstract There is an increasing interest in algae-based biomass produced outdoors in natural and industrial settings for biotechnological applications. To predict the yield and biochemical composition of the biomass, it is important to understand how the transcriptome of species and strains of interest is affected by seasonal changes. Here we studied the effects of Nordic winter and summer on the transcriptome of two phytoplankton species, namely the diatom Skeletonema marinoi (Sm) and the eustigmatophyte Nannochloropsis granulata (Ng), recently identified as potentially important for biomass production on the west coast of Sweden. Cultures were grown in photobioreactors in simulated Nordic summer and winter, and the gene expression in two phases was quantified by Illumina RNA-sequencing. Five paired comparisons were made among the four conditions. Sm was overall more responsive to seasons since 70 % of the total transcriptome (14,783 genes) showed differential expression in at least one comparison as compared to 1.6 % (1403 genes) for Ng. For both species, we observed larger differences between the seasons than between the phases of the same season. In summer phase 1, Sm cells focused on photosynthesis and polysaccharide biosynthesis. Nitrate assimilation and recycling of intracellular nitrogen for protein biosynthesis were more active in summer phase 2 and throughout winter. Lipid catabolism was upregulated in winter relative to summer to supply carbon for respiration. Ng favored lipid accumulation in summer, while in winter activated different lipid remodeling pathways as compared to Sm. To cope with winter, Ng upregulated breakdown and transport of carbohydrates for energy production. Taken together, our transcriptome data reveal insights into adaptive seasonal responses of Sm and Ng important for biotechnological applications on the west coast of Sweden, but more work is required to decipher the molecular mechanisms behind these responses.
10.	Johansson, Oskar N., 1984, et al. (författare) A quick and robust method for quantification of the hypersensitive response in plants 2015 Ingår i: Peerj. - : PeerJ. - 2167-8359. ; 3 Tidskriftsartikel (refereegranskat)abstract One of the most studied defense reactions of plants against microbial pathogens is the hypersensitive response (HR). The HR is a complex multicellular process that involves programmed cell death at the site of infection. A standard method to quantify plant defense and the HR is to measure the release of cellular electrolytes into water after infiltration with pathogenic bacteria. In this type of experiment, the bacteria are typically delivered into the plant tissue through syringe infiltration. Here we report the development of a vacuum infiltration protocol that allows multiple plant lines to be infiltrated simultaneously and assayed for defense responses. Vacuum infiltration did not induce more wounding response in Arabidopsis leaf tissue than syringe inoculation, whereas throughput and reproducibility were improved. The method was used to study HR-induced electrolyte loss after treatment with the bacterium Pseudomonas syringae pv. tomato DC3000 harboring the effector AvrRpm1, AvrRpt2 or AvrRps4. Specifically, the influence of bacterial titer on AvrRpm1-induced HR was investigated. Not only the amplitude, but also the timing of the maximum rate of the HR reaction was found to be dose-dependent. Finally, using vacuum infiltration, we were able quantify induction of phospholipase D activity after AvrRpm1 recognition in leaves labeled with (PO4)-P-33.
11.	Johansson, Oskar N., 1984, et al. (författare) Phenomics reveals a novel putative chloroplast fatty acid transporter in the marine diatom Skeletonema marinoi involved in temperature acclimation 2019 Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9 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.
12.	Johansson, Oskar N., 1984, et al. (författare) Redundancy among phospholipase D isoforrns in resistance triggered by recognition of the Pseudomonas syringae effector AyrRpm1 in Arabidopsis thaliana 2014 Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 5 Tidskriftsartikel (refereegranskat)abstract Plants possess a highly sophisticated system for defense against microorganisms. So called MAMP (microbe-associated molecular patterns) triggered immunity (MTI) prevents the majority of non-adapted pathogens from causing disease. Adapted plant pathogens use secreted effector proteins to interfere with such signaling. Recognition of microbial effectors or their activity by plant resistance (R)-proteins triggers a second line of defense resulting in effector triggered immunity (ETI). The latter usually comprises the hypersensitive response (HR) which includes programmed cell death at the site of infection. Phospholipase D (PLD) mediated production of phosphatidic acid (PA) has been linked to both MTI and ETI in plants. Inhibition of PLD activity has been shown to attenuate MTI as well as ETI. In this study, we systematically tested single and double knockouts in all 12 genes encoding PLDs in Arabidopsis thaliana for effects on ETI and MTI. No single PLD could be linked to ETI triggered by recognition of effectors secreted by the bacterium Pseudomonas syringae. However, repression of PLD dependent PA production by n-butanol strongly inhibited the HR following Pseudomonas syringae effector recognition. In addition some p/d mutants were more sensitive to n-butanol than wild type. Thus, the effect of mutations of PLDs could become detectable, and the corresponding genes can be proposed to be involved in the HR. Only knockout of PLEA caused a loss of MTI-induced cell wall based defense against the non-host powdery mildew Erysiphe pisi. This is thus in stark contrast to the involvement of a multitude of PLD isoforms in the HR triggered by AvrRpm1 recognition.
13.	Kourtchenko, Olga, 1980, et al. (författare) Oxo-phytodienoic acid-containing galactolipids in arabidopsis: Jasmonate signaling dependence 2007 Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 145:4, s. 1658-1669 Tidskriftsartikel (refereegranskat)abstract The jasmonate family of phytohormones, as represented by 12-oxo-phytodienoic acid (OPDA), dinor-phytodienoic acid (dn-OPDA), and jasmonic acid in Arabidopsis (Arabidopsis thaliana), has been implicated in a vast array of different developmental processes and stress responses. Recent reports indicate that OPDA and dn-OPDA occur not only as free acids in Arabidopsis, but also as esters with complex lipids, so-called arabidopsides. Recently, we showed that recognition of the two bacterial effector proteins AvrRpm1 and AvrRpt2 induced high levels of a molecule consisting of two OPDAs and one dn-OPDA esterified to a monogalactosyl diacylglycerol moiety, named arabidopside E. In this study, we demonstrate that the synthesis of arabidopsides is mainly independent of the prokaryotic lipid biosynthesis pathway in the chloroplast, and, in addition to what previously has been reported, arabidopside E as well as an all-OPDA analog, arabidopside G, described here accumulated during the hypersensitive response and in response to wounding. We also show that different signaling pathways lead to the formation of arabidopsides during the hypersensitive response and the wounding response, respectively. However, the formation of arabidopsides during both responses is dependent on an intact jasmonate signaling pathway. Additionally, we report inhibition of growth of the fungal necrotrophic pathogen Botrytis cinerea and in planta release of free jasmonates in a time frame that overlaps with the observed reduction of arabidopside levels. Thus, arabidopsides may have a dual function: as antipathogenic substances and as storage compounds that allow the slow release of free jasmonates.
14.	Lindsay, Willow, 1980, et al. (författare) Seasonal but not sex-biased gene expression of the carotenoid ketolase, CYP2J19, in the sexually dichromatic southern red bishop (Euplectes orix) 2022 Ingår i: Royal Society Open Science. - : The Royal Society. - 2054-5703. ; 9:8 Tidskriftsartikel (refereegranskat)abstract Intense red colours in birds are often owing to ketocarotenoids (KCs). In many land birds, KCs are oxidized from dietary yellow precursors, presumably by the avian carotenoid ketolase CYP2J19, the regulation and constraints of which have important implications for condition-dependence and honest signalling of carotenoid colour displays. We investigated hepatic CYP2J19 gene expression in the seasonally and sexually dichromatic southern red bishop (Euplectes orix) in relation to season, sex, progression of the prenuptial moult, testis size, body condition, redness and circulating sex steroids. A coloration function of CYP2J19 is supported by a seasonal upregulation prior to and during the carotenoid-depositing stage of the male prenuptial moult. However, CYP2J19 expression was similarly high in females (which do not moult prenuptially), and remained high in males after moult, suggesting additional or alternative roles of hepatic CYP2J19 or its products, such as detoxification or antioxidant functions. In males, the CYP2J19 upregulation preceded and was unrelated to the rise in plasma testosterone, but was correlated with androstenedione, probably of adrenal origin and compatible with luteinizing hormone-induced and (in females) oestrogen-suppressed moult. Finally, contrary to ideas that carotenoid ketolation rate mediates honest signalling of male quality, CYP2J19 expression was not related to plumage redness or male body condition.
15.	Najm, Svetlana, et al. (författare) Effects of a lipid emulsion containing fish oil on polyunsaturated fatty acid profiles, growth and morbidities in extremely premature infants: A randomized controlled trial 2017 Ingår i: Clinical Nutrition ESPEN. - : Elsevier BV. - 2405-4577. ; 20, s. 17-23 Tidskriftsartikel (refereegranskat)abstract © 2017 The Authors Background & aims The purpose of the study was to compare the effects of the parenteral emulsion SMOFlipid ® , with 15% fish oil, with Clinoleic ® on retinopathy of prematurity (ROP) and other morbidities and growth, and to compare their impact on longitudinal serum levels of fatty acids. Retinopathy of prematurity, other morbidity and growth were correlated with each parenteral lipid supplement. Methods Ninety infants born at gestational age < 28 weeks were randomized to treatment with SMOFlipid ® or Clinoleic ® . Two thirds (66%) of the infants received parenteral nutrition for up to 14 days birth (median 8, range 2–14 days), and additional 25% of the infants received for up to 28 days after birth (median 21, range 15–28 days). Cord blood samples and then venous blood samples were obtained at ages 1, 7, 14, and 28 days and at postmenstrual age (PMA) 32, 36, and 40 weeks. Breastmilk was collected at postnatal day 7, and at PMA 32 and 40 weeks. Serum phospholipid and breastmilk total fatty acids were analyzed by gas chromatography–mass spectrometry. Treatment groups were compared with regard to ROP, bronchopulmonary dysplasia, necrotizing enterocolitis, patent ductus arteriosus sepsis and growth between birth and 36 weeks. Results Infants on SMOFlipid ® had higher fractions of omega-3 LCPUFA eicosapentaenoic acid (EPA) and slightly higher omega-3 LCPUFA docosahexaenoic acid (DHA) fraction and a decreased arachidonic acid (AA) to DHA ratio from one week after birth up to 32 postmenstrual weeks compared to infants on Clinoleic ® . Treatment groups did not differ in morbidities or growth. Conclusion Supplementation with SMOFlipid ® containing 15% fish oil during parenteral nutrition increased EPA substantially, DHA marginally, reduced AA and decreased AA to DHA ratio. It did not reduce morbidity or affect growth. Since extremely preterm infants accumulate a large deficit of DHA and AA, studies on more prolonged or different levels of DHA and AA supplementation are warranted.
16.	Nilsson, Anders K., 1982, et al. (författare) Formation of oxidized phosphatidylinositol and 12-oxo-phytodienoic acid containing acylated phosphatidylglycerol during the hypersensitive response in Arabidopsis 2014 Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422. ; 101, s. 65-75 Tidskriftsartikel (refereegranskat)abstract Plant membranes are composed of a wide array of polar lipids. The functionality of these extends far beyond a pure structural role. Membrane lipids function as enzyme co-factors, establish organelle identity and as substrates for enzymes such as lipases and lipoxygenases. Enzymatic degradation or oxidation (enzymatic or non-enzymatic) of membrane lipids leads to the formation of a diverse group of bioactive compounds. Plant defense reactions provoked by pathogenic microorganisms are often associated with substantial modifications of the lipidome. In this study, we profiled changes in phospholipids during the hypersensitive response triggered by recognition of the bacterial effector protein AvrRpm1 in Arabidopsis thaliana. A simple and robust LC-MS based method for profiling plant lipids was designed to separate all the major species of glycerolipids extracted from Arabidopsis leaf tissue. The method efficiently separated several isobaric and near isobaric lipid species, which otherwise are difficult to quantify in direct infusion based profiling. In addition to the previously reported OPDA-containing galactolipids found to be induced during hypersensitive response in Arabidopsis, three OPDA-containing sulfoquinovosyl diacylglycerol species, one phosphatidylinositol species as well as two acylated OPDA-containing phosphatidylglycerol species were found to accumulate during the hypersensitive response in Arabidopsis. Our study confirms and extends on the notion that the hypersensitive response in Arabidopsis triggers a unique profile of Allene Oxide Synthase dependent oxidation of membrane lipids. Primary targets of this oxidation seem to be uncharged and anionic lipid species. (C) 2014 Elsevier Ltd. All rights reserved.
17.	Nilsson, Anders K., 1982, et al. (författare) Oxo-phytodienoic acid (OPDA) is formed on fatty acids esterified to galactolipids after tissue disruption in Arabidopsis thaliana 2012 Ingår i: Febs Letters. - : Wiley. - 0014-5793. ; 586:16, s. 2483-2487 Tidskriftsartikel (refereegranskat)abstract Biotic and abiotic stress induces the formation of galactolipids esterified with the phytohormones 12-oxo-phytodienoic acid (OPDA) and dinor-oxo-phytodienoic acid (dnOPDA) in Arabidopsis thaliana. The biosynthetic pathways of free (dn)OPDA is well described, but it is unclear how they are incorporated into galactolipids. We herein show that (dn)OPDA containing lipids are formed rapidly after disruption of cellular integrity in leaf tissue. Five minutes after freeze-thawing, 60-70% of the trienoic acids esterified to chloroplast galactolipids are converted to (dn)OPDA. Stable isotope labeling with O-18-water provides strong evidence for that the fatty acids remain attached to galactolipids during the enzymatic conversion to (dn)OPDA. (c) 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
18.	Nilsson, Anders K., 1982, et al. (författare) The activity of HYDROPEROXIDE LYASE 1 regulates accumulation of galactolipids containing 12-oxo-phytodienoic acid in Arabidopsis 2016 Ingår i: Journal of Experimental Botany. - : Oxford University Press (OUP). - 0022-0957 .- 1460-2431. ; 67:17, s. 5133-5144 Tidskriftsartikel (refereegranskat)abstract Arabidopsis produces galactolipids containing esters of 12-oxo-phytodienoic acid (OPDA) and dinor-12-oxo-phytodienoic acid (dnOPDA). These lipids are referred to as arabidopsides and accumulate in response to abiotic and biotic stress. We explored the natural genetic variation found in 14 different Arabidopsis accessions to identify genes involved in the formation of arabidopsides. The accession C24 was identified as a poor accumulator of arabidopsides whereas the commonly used accession Col-0 was found to accumulate comparably large amounts of arabidopsides in response to tissue damage. A quantitative trait loci analysis of an F-2 population created from a cross between C24 and Col-0 located a region on chromosome four strongly linked to the capacity to form arabidopsides. Expression analysis of HYDROPEROXIDE LYASE 1 (HPL1) showed large differences in transcript abundance between accessions. Transformation of Col-0 plants with the C24 HPL1 allele under transcriptional regulation of the 35S promoter revealed a strong negative correlation between HPL1 expression and arabidopside accumulation after tissue damage, thereby strengthening the view that HPL1 competes with ALLENE OXIDE SYNTHASE (AOS) for lipid-bound hydroperoxide fatty acids. We further show that the last step in the synthesis of galactolipid-bound OPDA and dnOPDA from unstable allene oxides is exclusively enzyme-catalyzed and not the result of spontaneous cyclization. Thus, the results presented here together with previous studies suggest that all steps in arabidopside biosynthesis are enzyme-dependent and apparently all reactions can take place with substrates being esterified to galactolipids.
19.	Park, S. W., et al. (författare) Cyclophilin 20-3 relays a 12-oxo-phytodienoic acid signal during stress responsive regulation of cellular redox homeostasis 2013 Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 110:23, s. 9559-9564 Tidskriftsartikel (refereegranskat)abstract The jasmonate family of phytohormones plays central roles in plant development and stress acclimation. However, the architecture of their signaling circuits remains largely unknown. Here we describe a jasmonate family binding protein, cyclophilin 20-3 (CYP20-3), which regulates stress-responsive cellular redox homeostasis. (+)-12-oxo-phytodienoic acid (OPDA) binding promotes CYP20-3 to form a complex with serine acetyltransferase 1, which triggers the formation of a hetero-oligomeric cysteine synthase complex with O-acetylserine (thiol) lyase B in chloroplasts. The cysteine synthase complex formation then activates sulfur assimilation that leads to increased levels of thiol metabolites and the buildup of cellular reduction potential. The enhanced redox capacity in turn coordinates the expression of a subset of OPDA-responsive genes. Thus, we conclude that CYP20-3 is a key effector protein that links OPDA signaling to amino acid biosynthesis and cellular redox homeostasis in stress responses.
20.	Pinosa, Francesco, et al. (författare) Arabidopsis Phospholipase D delta Is Involved in Basal Defense and Nonhost Resistance to Powdery Mildew Fungi 2013 Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 163:2, s. 896-906 Tidskriftsartikel (refereegranskat)abstract Plants have evolved a complex array of defensive responses against pathogenic microorganisms. Recognition of microbes initiates signaling cascades that activate plant defenses. The membrane lipid phosphatidic acid, produced by phospholipase D (PLD), has been shown to take part in both abiotic and biotic stress signaling. In this study, the involvement of PLD in the interaction between Arabidopsis (Arabidopsis thaliana) and the barley powdery mildew fungus Blumeria graminis f. sp. hordei (Bgh) was investigated. This nonadapted pathogen is normally resisted by a cell wall-based defense, which stops the fungal hyphae from penetrating the epidermal cell wall. Chemical inhibition of phosphatidic acid production by PLD increased the penetration rate of Bgh spores on wild-type leaves. The analysis of transfer DNA knockout lines for all Arabidopsis PLD genes revealed that PLD delta is involved in penetration resistance against Bgh, and chemical inhibition of PLDs in plants mutated in PLD delta indicated that this isoform alone is involved in Bgh resistance. In addition, we confirmed the involvement of PLD delta in penetration resistance against another nonadapted pea powdery mildew fungus, Erysiphe pisi. A green fluorescent protein fusion of PLD delta localized to the plasma membrane at the Bgh attack site, where it surrounded the cell wall reinforcement. Furthermore, in the pld delta mutant, transcriptional up-regulation of early microbe-associated molecular pattern response genes was delayed after chitin stimulation. In conclusion, we propose that PLD is involved in defense signaling in nonhost resistance against powdery mildew fungi and put PLD delta forward as the main isoform participating in this process.
21.	Tarvainen, Lasse, 1977, et al. (författare) Handling the heat - photosynthetic thermal stress in tropical trees. 2022 Ingår i: The New phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 233:1, s. 236-50 Tidskriftsartikel (refereegranskat)abstract Warming climate increases the risk for harmful leaf temperatures in terrestrial plants, causing heat stress and loss of productivity. The heat sensitivity may be particularly high in equatorial tropical tree species adapted to a thermally stable climate. Thermal thresholds of the photosynthetic system of sun-exposed leaves were investigated in three tropical montane tree species native to Rwanda with different growth and water use strategies (Harungana montana, Syzygium guineense and Entandrophragma exselsum). Measurements of chlorophyll fluorescence, leaf gas exchange, morphology, chemistry and temperature were made at three common gardens along an elevation/temperature gradient. Heat tolerance acclimated to maximum leaf temperature (Tleaf ) across the species. At the warmest sites, the thermal threshold for normal function of photosystem II was exceeded in the species with the highest Tleaf despite their higher heat tolerance. This was not the case in the species with the highest transpiration rates and lowest Tleaf . The results point to two differently effective strategies for managing thermal stress: tolerance through physiological adjustment of leaf osmolality and thylakoid membrane lipid composition, or avoidance through morphological adaptation and transpiratory cooling. More severe photosynthetic heat stress in low-transpiring montane climax species may result in a competitive disadvantage compared to high-transpiring pioneer species with more efficient leaf cooling.
22.	Torstensson, Anders, et al. (författare) Synergism between elevated pCO2 and temperature on the Antarctic sea ice diatom Nitzschia lecointei 2013 Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 10, s. 6391-6401 Tidskriftsartikel (refereegranskat)abstract Polar oceans are particularly susceptible to ocean acidification and warming. Diatoms play a significant role in sea ice biogeochemistry and provide an important food source to grazers in ice-covered oceans, especially during early spring. However, the ecophysiology of ice-living organisms has received little attention in terms of ocean acidification. In this study, the synergism between temperature and partial pressure of CO2 (pCO2) was investigated in relationship to the optimal growth temperature of the Antarctic sea ice diatom Nitzschia lecointei. Diatoms were kept in cultures at controlled levels of pCO2 (∼390 and ∼960 μatm) and temperature (−1.8 and 2.5 °C) for 14 days. Synergism between temperature and pCO2 was detected in growth rate and acyl lipid fatty acid (FA) content. Optimal growth rate was observed around 5 °C in a separate experiment. Carbon enrichment only promoted (6%) growth rate closer to the optimal growth, but not at the control temperature (−1.8 °C). At −1.8 °C and at ∼960 μatm pCO2, the total FA content was reduced relative to the ∼390 μatm treatment, although no difference between pCO2 treatments was observed at 2.5 °C. A large proportion (97%) of the total FAs comprised on average of polyunsaturated fatty acids (PUFA) at −1.8 °C. Cellular PUFA content was reduced at ∼960 relative to ∼390 μatm pCO2. Effects of carbon enrichment may be different depending on ocean warming scenario or season, e.g. reduced cellular FA content in response to elevated CO2 at low temperatures only, reflected as reduced food quality for higher trophic levels. Synergy between warming and acidification may be particularly important in polar areas since a narrow thermal window generally limits cold-water organisms.
23.	Wittemann, Maria, et al. (författare) Temperature acclimation of net photosynthesis and its underlying component processes in four tropical tree species 2022 Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 42:6, s. 1188-1202 Tidskriftsartikel (refereegranskat)abstract The effect of temperature change on leaf physiology has been extensively studied in temperate trees and to some extent in boreal and tropical tree species. While increased temperature typically stimulates leaf CO2 assimilation and tree growth in high-altitude ecosystems, tropical species are often negatively affected. These trees may operate close to their temperature optima and have a limited thermal acclimation capacity due to low seasonal and historical variation in temperature. To test this hypothesis, we studied the extent to which the temperature sensitivities of leaf photosynthesis and respiration acclimate to growth temperature in four common African tropical tree species. Tree seedlings native to different altitudes and therefore adapted to different growth temperatures were cultivated at three different temperatures in climate-controlled chambers. We estimated the acclimation capacity of the temperature sensitivities of light-saturated net photosynthesis, the maximum rates of Rubisco carboxylation (V-cmax) and thylakoid electron transport (J), and dark respiration. Leaf thylakoid membrane lipid composition, nitrogen content and leaf mass per area were also analyzed. Our results showed that photosynthesis in tropical tree species acclimated to higher growth temperatures, but that this was weakest in the species originating from the coolest climate. The temperature optimum of J acclimated significantly in three species and variation in J was linked to changes in the thylakoid membrane lipid composition. For V-cmax, there was only evidence of significant acclimation of optimal temperature in the lowest elevation species. Respiration acclimated to maintain homeostasis at growth temperature in all four species. Our results suggest that the lowest elevation species is better physiologically adapted to acclimate to high growth temperatures than the highest elevation species, indicating a potential shift in competitive balance and tree community composition to the disadvantage of montane tree species in a warmer world.
24.	Adolfsson, Lisa, 1984, et al. (författare) Mycorrhiza Symbiosis Increases the Surface for Sunlight Capture in Medicago truncatula for Better Photosynthetic Production 2015 Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:1 Tidskriftsartikel (refereegranskat)abstract Arbuscular mycorrhizal (AM) fungi play a prominent role in plant nutrition by supplying mineral nutrients, particularly inorganic phosphate (Pi), and also constitute an important carbon sink. AM stimulates plant growth and development, but the underlying mechanisms are not well understood. In this study, Medicago truncatula plants were grown with Rhizophagus irregularis BEG141 inoculum (AM), mock inoculum (control) or with Pi fertilization. We hypothesized that AM stimulates plant growth through either modifications of leaf anatomy or photosynthetic activity per leaf area. We investigated whether these effects are shared with Pi fertilization, and also assessed the relationship between levels of AM colonization and these effects. We found that increased Pi supply by either mycorrhization or fertilization led to improved shoot growth associated with increased nitrogen uptake and carbon assimilation. Both mycorrhized and Pi-fertilized plants had more and longer branches with larger and thicker leaves than the control plants, resulting in an increased photosynthetically active area. AM-specific effects were earlier appearance of the first growth axes and increased number of chloroplasts per cell section, since they were not induced by Pi fertilization. Photosynthetic activity per leaf area remained the same regardless of type of treatment. In conclusion, the increase in growth of mycorrhized and Pi-fertilized Medicago truncatula plants is linked to an increase in the surface for sunlight capture, hence increasing their photosynthetic production, rather than to an increase in the photosynthetic activity per leaf area.
25.	Amato, Alberto, et al. (författare) Grazer-induced transcriptomic and metabolomic response of the chain-forming diatom Skeletonema marinoi 2018 Ingår i: ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 12, s. 1594-1604 Tidskriftsartikel (refereegranskat)abstract Diatoms and copepods are main actors in marine food webs. The prey-predator interactions between them affect bloom dynamics, shape marine ecosystems and impact the energy transfer to higher trophic levels. Recently it has been demonstrated that the presence of grazers may affect the diatom prey beyond the direct effect of grazing. Here, we investigated the response of the chain-forming centric diatom Skeletonema marinoi to grazer cues, including changes in morphology, gene expression and metabolic profile. S. marinoi cells were incubated with Calanus finmarchicus or with Centropages typicus and in both cases responded by reducing the chain length, whereas changes in gene expression indicated an activation of stress response, changes in the lipid and nitrogen metabolism, in cell cycle regulation and in frustule formation. Transcripts linked to G protein-coupled receptors and to nitric oxide synthesis were differentially expressed suggesting involvement of these signalling transduction pathways in the response. Downregulation of a lipoxygenase in the transcriptomic data and of its products in the metabolomic data also indicate an involvement of oxylipins. Our data contribute to a better understanding of the gene function in diatoms, providing information on the nature of genes implicated in the interaction with grazers, a crucial process in marine ecosystems.

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