| 1. |
- Aman, Robert, 1982-
(författare)
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Impossible Interculturality? : Education and the Colonial Difference in a Multicultural World
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An increasing number of educational policies, academic studies, and university courses today propagate ‘interculturality’ as a method for approaching ‘the Other’ and reconciling universal values and cultural specificities. Based on a thorough discussion of Europe’s colonial past and the hierarchies of knowledge that colonialism established, this dissertation interrogates the definitions of intercultural knowledge put forth by EU policy discourse, academic textbooks on interculturality, and students who have completed a university course on the subject. Taking a decolonial approach that makes its central concern the ways in which differences are formed and sustained through references to cultural identities, this study shows that interculturality, as defined in these texts, runs the risk of affirming a singular European outlook on the world, and of elevating this outlook into a universal law. Contrary to its selfproclaimed goal of learning from the Other, interculturality may in fact contribute to the repression of the Other by silencing those who are already muted. The dissertation suggests an alternative definition of interculturality, which is not framed in terms of cultural differences but in terms of colonial difference. This argument is substantiated by an analysis of the Latin American concept of interculturalidad, which derives from the struggles for public and political recognition among indigenous social movements in Bolivia, Ecuador and Peru. By bringing interculturalidad into the picture, with its roots in the particular and with strong reverberations of the historical experience of colonialism, this study explores the possibility of decentring the discourse of interculturality and its Eurocentric outlook. In this way, the dissertation argues that an emancipation from colonial legacies requires that we start seeing interculturality as inter-epistemic rather than simply inter-cultural.
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| 2. |
- Arnqvist, Lisa, 1970-, et al.
(författare)
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Overexpression of CYP710A1 and CYP710A4 in transgenic Arabidopsis plants increases the level of stigmasterol at the expense of sitosterol
- 2008
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Ingår i: Planta. - : Springer Science and Business Media LLC. - 0032-0935 .- 1432-2048. ; 227:2, s. 309-317
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Tidskriftsartikel (refereegranskat)abstract
- Sitosterol and stigmasterol are major sterols in vascular plants. An altered stigmasterol:sitosterol ratio has been proposed to influence the properties of cell membranes, particularly in relation to various stresses, but biosynthesis of stigmasterol is poorly understood. Recently, however, Morikawa et al. (Plant Cell 18:1008–1022, 2006) showed in Arabidopsis thaliana that synthesis of stigmasterol and brassicasterol is catalyzed by two separate sterol C-22 desaturases, encoded by the genes CYP710A1 and CYP710A2, respectively. The proteins belong to a small cytochrome P450 subfamily having four members, denoted by CYP710A1-A4, and are related to the yeast sterol C-22 desaturase Erg5p acting in ergosterol synthesis. Here, we report on our parallel investigation of the Arabidopsis CYP710A family. To elucidate the function of CYP710A proteins, transgenic Arabidopsis plants were generated overexpressing CYP710A1 and CYP710A4. Compared to wild-type plants, both types of transformant displayed a normal phenotype, but contained increased levels of free stigmasterol and a concomitant decrease in the level of free sitosterol. CYP710A1 transformants also displayed higher levels of esterified forms of stigmasterol, cholesterol, 24-methylcholesterol and isofucosterol. The results confirm the findings of Morikawa et al. (Plant Cell 18:1008–1022, 2006) regarding the function of CYP710A1 in stigmasterol synthesis, and show that CYP710A4 also has this capacity. Furthermore, our results suggest that an increased stigmasterol level alone is sufficient to stimulate esterification of other major sterols.
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| 3. |
- Arnqvist, L, et al.
(författare)
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Reduction of cholesterol and glycoalkaloid levels in transgenic potato plants by overexpression of a type 1 sterol methyltransferase cDNA
- 2003
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 131:4, s. 1792-1799
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Tidskriftsartikel (refereegranskat)abstract
- Transgenic potato (Solanum tuberosum cv Desiree) plants overexpressing a soybean (Glycine max) type 1 sterol methyltransferase (GmSMT1) cDNA were generated and used to study sterol biosynthesis in relation to the production of toxic glycoalkaloids. Transgenic plants displayed an increased total sterol level in both leaves and tubers, mainly due to increased levels of the 24-ethyl sterols isofucosterol and sitosterol. The higher total sterol level was due to increases in both free and esterified sterols. However, the level of free cholesterol, a nonalkylated sterol, was decreased. Associated with this was a decreased glycoalkaloid level in leaves and tubers, down to 41% and 63% of wild-type levels, respectively. The results show that glycoalkaloid biosynthesis can be down-regulated in transgenic potato plants by reducing the content of free nonalkylated sterols, and they support the view of cholesterol as a precursor in glycoalkaloid biosynthesis.
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| 4. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 5. |
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| 6. |
- Beste, Lisa, et al.
(författare)
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Synthesis of Hydroxylated Sterols in Transgenic Arabidopsis Plants Alters Growth and Steroid Metabolism
- 2011
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 157:1, s. 426-440
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Tidskriftsartikel (refereegranskat)abstract
- To explore mechanisms in plant sterol homeostasis, we have here increased the turnover of sterols in Arabidopsis (Arabidopsis thaliana) and potato (Solanum tuberosum) plants by overexpressing four mouse cDNA encoding cholesterol hydroxylases (CHs), hydroxylating cholesterol at the C-7, C-24, C-25, or C-27 positions. Compared to the wild type, the four types of Arabidopsis transformant showed varying degrees of phenotypic alteration, the strongest one being in CH25 lines, which were dark-green dwarfs resembling brassinosteroid-related mutants. Gas chromatography-mass spectrometry analysis of extracts from wild-type Arabidopsis plants revealed trace levels of alpha and beta forms of 7-hydroxycholesterol, 7-hydroxycampesterol, and 7-hydroxysitosterol. The expected hydroxycholesterol metabolites in CH7-, CH24-, and CH25 transformants were identified and quantified using gas chromatography-mass spectrometry. Additional hydroxysterol forms were also observed, particularly in CH25 plants. In CH24 and CH25 lines, but not in CH7 ones, the presence of hydroxysterols was correlated with a considerable alteration of the sterol profile and an increased sterol methyltransferase activity in microsomes. Moreover, CH25 lines contained clearly reduced levels of brassinosteroids, and displayed an enhanced drought tolerance. Equivalent transformations of potato plants with the CH25 construct increased hydroxysterol levels, but without the concomitant alteration of growth and sterol profiles observed in Arabidopsis. The results suggest that an increased hydroxylation of cholesterol and/or other sterols in Arabidopsis triggers compensatory processes, acting to maintain sterols at adequate levels.
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| 7. |
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| 8. |
- Dahlin, Paul, 1983-
(författare)
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Analysis of sterol metabolism in the pathogenic oomycetes Saprolegnia parasitica and Phytophthora infestans
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The primary objective of this thesis was to investigate the sterol metabolism of two pathogenic oomycetes, specifically the processes of sterol synthesis and sterol acquisition in the fish pathogen Saprolegnia parasitica (Saprolegniales) and the plant pathogen Phytophthora infestans (Peronosporales). Furthermore, the effects of steroidal glycoalkaloids from Solanaceous plants, on P. infestans, were examined. The improved understanding of these processes should help to identify approaches for the identification of new oomycete inhibitors targeting sterol metabolism in agriculture and aquaculture farming systems, and to guide plant-breeding strategies to defend solanaceous plants against oomycetes.For these reasons, the molecular basis of the metabolic pathways of sterol synthesis and/or sterol acquisition was investigated. Sterols are derived from isoprenoids and indispensable in various biological processes. Our biochemical investigation of an oxidosqualene cyclase revealed that sterol synthesis in S. parasitica begins with the formation of lanosterol (Paper I), and a reconstruction of the complete sterol synthesis pathway to the final compound, fucosterol, in S. parasitica was performed using bioinformatics (Paper II). Complementary to this work, the extent to which P. infestans, which is incapable of de novo sterol synthesis, is able to modify exogenously provided sterols was investigated by determining the growth impact of various sterol supplements in the growth media (Paper II). Building on the sterol investigations, the solanaceous sterol derivatives from the glycoalkaloid family were analysed. These compounds contain both a steroidal and a carbohydrate (glycan) moiety. Data obtained by feeding various deuterium-labeled sterols to potato shoots, supported the theory that steroidal glycoalkaloids in Solanum tuberosum are produced from cholesterol (Paper III). Since these steroidal glycoalkaloids are thought to play a role in plant defense, their physiological effects on P. infestans were investigated (Paper IV). Unexpectedly we found that non-glycosylated steroidal alkaloids had a greater inhibitory effect than steroidal glycoalkaloids. Steroidal glycoalkaloids derived from other Solanaceous species exhibited different physiological effects on the growth of P. infestans. This research was conducted on two oomycete species belonging to the Saprolegniales and Peronosporales orders, hence the results presented are likely to be representative of each of these two oomycete orders.
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| 9. |
- Delp, Gabriele, et al.
(författare)
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Microarray analysis of the interaction between the aphid Rhopalosiphum padi and host plants reveals both differences and similarities between susceptible and partially resistant barley lines
- 2009
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Ingår i: Molecular Genetics and Genomics. - : Springer Science and Business Media LLC. - 1617-4615 .- 1617-4623. ; 281:3, s. 233-248
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Tidskriftsartikel (refereegranskat)abstract
- The bird cherry-oat aphid (Rhopalosiphum padi L.) is an important pest on cereals causing plant growth reduction without specific leaf symptoms. Breeding of barley (Hordeum vulgare L.) for R. padi resistance shows that there are several resistance genes, reducing aphid growth. To identify candidate sequences for resistance-related genes, we performed microarray analysis of gene expression after aphid infestation in two susceptible and two partially resistant barley genotypes. One of the four lines is a descendant of two of the other genotypes. There were large differences in gene induction between the four lines, indicating substantial variation in response even between closely related genotypes. Genes induced in aphid-infested tissue were mainly related to defence, primary metabolism and signalling. Only 24 genes were induced in all lines, none of them related to oxidative stress or secondary metabolism. Few genes were down-regulated, with none being common to all four lines. There were differences in aphid-induced gene regulation between resistant and susceptible lines. Results from control plants without aphids also revealed differences in constitutive gene expression between the two types of lines. Candidate sequences for induced and constitutive resistance factors have been identified, among them a proteinase inhibitor, a serine/threonine kinase and several thionins.
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| 10. |
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| 11. |
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| 12. |
- Garcia, Alejandro, et al.
(författare)
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Guaranteed periodic real-time communication over wormhole switched networks
- 2000
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Ingår i: Parallel and distributed computing systems. - Raleigh, NC : INTERNATIONAL SOCIETY COMPUTERS & THEIR APPLICATIONS (ISCA). - 188084334X ; , s. 632-639
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Konferensbidrag (refereegranskat)abstract
- In this paper, we investigate how to efficiently implement TDMA (Time Division Multiple Access) on a wormhole switched network using a pure software solution in the end nodes. Transmission is conflict free on the time-slot level and hence deadlock free. On the sub- slot level, however, conflicts are possible when using early sending, a method we propose in order to reduce latency while still not hazarding the TDMA schedule. We propose a complete system to offer services for dynamic establishment of guaranteed periodic real-time virtual channels. Two different clock synchronization approaches for integration into the TDMA system are discussed. Implementation and experimental studies have been done on a cluster of PCs connected by a Myrinet network. Also, a case study with a radar signal processing application is presented to show the usability. A best-case reduction of the latency of up to 37 percent for 640 Byte messages by using early sending in Myrinet is shown in the case study. Source routed wormhole switching networks are assumed in the work but the results are applicable on some other categories of switched networks too.
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| 13. |
- Glinwood, R., et al.
(författare)
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Aphid acceptance of barley exposed to volatile phytochemicals differs between plants exposed in daylight and darkness
- 2007
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Ingår i: Plant Signalling & Behavior. - 1559-2316 .- 1559-2324. ; 2:5, s. 321-326
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that volatile cues from damaged plants may induce resistance in neighboring plants. Much less is known about the effects of volatile interaction between undamaged plants. In this study, barley plants, Hordeum vulgare cv. Kara, were exposed to volatiles from undamaged plants of barley cv. Alva or thistle Cirsium vulgare, and to the volatile phytochemicals, methyl salicylate or methyl jasmonate. Exposures were made either during natural daylight or darkness. Acceptance of exposed plants by the aphid Rhopalosiphum padi was assessed, as well as the expression of putative marker genes for the different treatments. Aphid acceptance of plants exposed to either barley or C. vulgare was significantly reduced, and an effect of the volatiles from undamaged plants was confirmed by the induction of pathogenesis-related protein, PR1a in exposed plants. However the effect on aphid acceptance was seen only when plants were exposed during darkness, whereas PR1a was induced only after treatment during daylight. Aphid acceptance of plants exposed to either methyl salicylate or methyl jasmonate was significantly reduced, but only when plants were exposed to the chemicals during daylight. AOS2 (allene oxide synthase) was induced by methyl jasmonate and BCI-4 (barley chemical inducible gene-4) by methyl salicylate in both daylight and darkness. It is concluded that (a) the effects on aphids of exposing barley to volatile phytochemicals was influenced by the presence or absence of light and (b) the response of barley to methyl salicylate/methyl jasmonate and to volatiles from undamaged plants differed at the gene and herbivore level.
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| 14. |
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| 15. |
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| 16. |
- Hamada, Afaf M., et al.
(författare)
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Thiamine treatments alleviate aphid infestations in barley and pea
- 2013
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 94, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- Treatment of plants with thiamine (Vitamin B1) has before been shown to activate plant defence against microorganisms. Here, we have studied the effects of thiamine treatments of plants on aphid reproduction and behaviour. The work was mainly carried out with bird cherry-oat aphid (Rhopalosiphum padi L.) on barley (Hordeum vulgare L.). Aphid population growth and aphid acceptance on plants grown from seeds soaked in a 150 mu M thiamine solution were reduced to ca. 60% of that on control plants. R. padi life span and the total number of offspring were reduced on barley plants treated with thiamine. Healthy aphids and aphids infected with the R. padi virus were similarly affected. Spraying or addition of thiamine at 150 mu M to nutrient solutions likewise resulted in reduced aphid population growth to ca. 60%, as did plant exposure to thiamine odour at 4 mM. Thiamine treatments resulted in reduced aphid population growth also when tested with grain aphid (Sitobion avenae F.) on barley and pea aphid (Acyrthosiphon pisum H.) on pea (Pisum sativum L). There was no direct effect of thiamine on aphid reproduction or thiamine odour on aphid behaviour, as evaluated using artificial diets and by olfactometer tests, respectively. Two gene sequences regulated by salicylic acid showed higher transcript abundance and one gene sequence regulated by methyl jasmonate showed lower transcript abundance in thiamine-treated plants but not in control plants after aphid infestation. These results suggest that the aphid antibiosis and antixenosis effects may be related to priming of defence, but more studies are needed to explain the effects against aphids.
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| 17. |
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| 18. |
- Jonsson, Bibi, et al.
(författare)
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Anna Elisabet (Annalisa) Forssberger
- 2018
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Ingår i: Svenskt kvinnobiografiskt lexikon. - 2003-0088. - 9789163975943
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 19. |
- Jonsson, Bibi, et al.
(författare)
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Ebba Richert
- 2018
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Ingår i: Svenskt kvinnobiografiskt lexikon. - 2003-0088. - 9789163975943
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 20. |
- Jonsson, Bibi, et al.
(författare)
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Elin Mathilda Elisabeth Wägner
- 2018
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Ingår i: Svenskt kvinnobiografiskt lexikon. - 2003-0088. - 9789163975943
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 21. |
- Jonsson, Bibi, et al.
(författare)
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Elin Wägner 1882–1949
- 2019
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Ingår i: Märkvärdiga svenska kvinnor. : 200 kvinnor som förändrat våra liv - 200 kvinnor som förändrat våra liv. - 9789100179342 ; , s. 242-244
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Bokkapitel (populärvet., debatt m.m.)
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| 22. |
- Jonsson, Bibi, et al.
(författare)
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Margit Charlotta Söderholm
- 2018
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Ingår i: Svenskt kvinnobiografiskt lexikon. - 2003-0088. - 9789163975943
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 23. |
- Jonsson, Bibi, et al.
(författare)
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Sigrid Maria Fredrika Gillner
- 2018
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Ingår i: Svenskt kvinnobiografiskt lexikon. - 2003-0088. - 9789163975943
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 24. |
- Jonsson, Bibi, et al.
(författare)
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Solveig Viveka Starfelt
- 2018
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Ingår i: Svenskt kvinnobiografiskt lexikon. - 2003-0088. - 9789163975943
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 25. |
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| 27. |
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| 28. |
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| 29. |
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| 30. |
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| 31. |
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| 32. |
- Jonsson, Lisbeth G., 1955, et al.
(författare)
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Distributional patterns of macro- and megafauna associated with a reef of the cold-water coral Lophelia pertusa on the Swedish west coast
- 2004
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Ingår i: Marine Ecology Progress Series. - 1616-1599. ; 284, s. 163-171
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Tidskriftsartikel (refereegranskat)abstract
- In this study the distributional pattern of the macro- and megafauna of a small (ca. 300 m2) Lophelia pertusa (L., 1758) reef was studied with a ROV (remotely operated vehicle). The reef is situated in a shallow fjord off the Swedish west coast. The number of taxa and their abundance in transects from the reef itself and from 3 zones (Zone 1 = 50 m, Zone 2 = 100 m and Zone 3 = 200 m) around the reef were compared. Both the number of taxa (from 30 to 33 transect-1) and the abundance of individuals (from 21 to 7 m-2) decreased with increasing distance from the reef. Divided into ecological guilds, predators and filter-feeders decreased with distance from the reef (predators from 7 to 0.3 ind. m-2, and filter-feeders from 13 to 6 ind. m-2 from Zone 0 to Zone 3), while deposit-feeders increased with increasing distance from 0.04 to 0.4 ind. m-2 from Zone 0 to Zone 3. Sessile species decreased more with increasing distance than mobile species, from 19 to 7 ind. m-2 and from 1 to 0.7 ind. m-2, respectively. Our results also show that small deep-water coral reefs enhance local biodiversity, but the advantage to individual species depends on their mode of feeding and mobility.
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| 33. |
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| 37. |
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| 38. |
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| 39. |
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| 40. |
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| 41. |
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| 42. |
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| 43. |
- Jonsson, Lisbeth G., 1955, et al.
(författare)
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Symbiotic associations between anthozoans and crustaceans in a temperate coastal area
- 2001
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Ingår i: Marine Ecology Progress Series. - 0171-8630. ; 209, s. 189-195
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Tidskriftsartikel (refereegranskat)abstract
- While symbiotic associations between anemones and crustaceans appear to be common in tropical waters, few such associations are known from temperate waters, except for the symbiosis between hermit crabs and anemones. In this study, observations made with ROVs (remotely operated vehicles) suggested that certain shrimps (Pandalus borealis, P. propinquus, P. montagui and in particular Spirontocaris liljeborgii and Lebbeus polaris) associate with the anemone Bolocera tuediae and the cerianthid Pachycerianthus multiplicatus by aggregating beneath their tentacles. The lithodid crab Lithodes maja was also observed associating with B. tuediae. Laboratory experiments suggested that female crabs have a stronger association than males. The associations are presumably facultative commensalistic, as the species of crustaceans live as non-symbionts on the sea floor as well, and the 2 anthozoans do not seem to gain any benefits from the associations. In the field, S. liljeborgii had the closest association with both species of anthozoans, while B. tuediae was the preferred host of all associating species. The main benefit for the crustaceans to be associated with the anthozoans is protection against predators. In the case of the shrimps, access to a food source is probably also important.
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| 44. |
- Kristiansen, Lisbeth, 1965-, et al.
(författare)
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A health promotion intervention strengthening Swedish high school students' wellbeing: A feasibility study
- 2018
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Ingår i: British Journal of School Nursing. - : Mark Allen Group. - 1752-2803 .- 2052-2827. ; 13:6
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Tidskriftsartikel (refereegranskat)abstract
- The majority of Swedish school children enjoy a general good health. Still, mental health problems are increasing among young people in Sweden. According to Swedish law all school staff members (teachers and student health professionals) have mutual responsibility to provide a safe school environment and health. Since 2010, there is an emphasis on health promotion in schools. The aim of this study is to describe the feasibility and pilot outcomes of a health promoting intervention targeting healthy high school students (the Strengthening Adolescent Wellbeing [SAW] project).A descriptive design was used with an intervention group that was assessed before and after the implementation of the programme using quantitative methods. The study was based on the Medical Research Council Framework. The study and the data collection were performed during the autumnof 2016 and the early spring of 2017.Public high school students' health professionals, that is school nurses, student counselors and specialist educators, facilitated a research-based intervention consisting of eight sessions with education and mind-body practices. Pre- and post-testing were carried out.The main findings showed enhanced levels of wellbeing among the participating students and the student-related measures all showed improvements.The intervention seems to have been feasible in this context. Findings from this study indicate that the SAW methodology contributed to an improvement in high school students' wellbeing. The study will provide a base for a full-scale evaluation study intended to evaluate the effect of this health-promoting programme.
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| 45. |
- Larsson, Kristina A. E., et al.
(författare)
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Differential regulation of 3-aminomethylindole/N-methyl-3-aminomethylindole N-methyltransferase and gramine in barley by both biotic and abiotic stress conditions
- 2011
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Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 49:1, s. 96-102
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Tidskriftsartikel (refereegranskat)abstract
- The expression of NMT (3-aminomethylindole/N-methyl-3-aminomethylindole N-methyltransferase; EC 2.1.1.), involved in the biosynthesis of the indole alkaloid gramine, was investigated in aphid-infested barley (Hordeum vulgare L). NMT is induced by methyl jasmonate and it was hypothesized that the gene would be more strongly upregulated in aphid-resistant barley. We examined the effects of feeding by three aphid species; Russian wheat aphid (Diuraphis noxia Mordvilko), rose-grain aphid (Metopolophium dirhodum Walker) and bird cherry-oat aphid (Rhopalosiphum padi L.) on barley genotypes with varying resistance characteristics. The barley genotypes selected included the cultivar Libra, known to upregulate gramine after feeding by Schizaphis graminum. Infestation by R. padi and M. dirhodum resulted in higher NMT expression in the doubled haploid line 5172-28:4 (DH28:4), which has moderate resistance against R. padi, but not in other aphid barley combinations. None of the aphid plant combinations had however increased gramine, suggesting that aphid-induction of gramine is specific to S. graminum. The increased abundance of NMT transcript in aphid-infested DH28:4 did not lead to higher amounts of NMT protein or NMT enzyme activity, neither did 200 times upregulation of NMT transcript in cotyledons incubated with methyl jasmonate, illustrating that even large differences measured at transcript level may have no metabolic consequences. Drought stress or treatments with abscisic acid did lead to higher gramine concentrations in several barley cultivars, but without any concomitant increase of NMT transcripts. Thus, the regulation of the biosynthetic pathway to gramine at transcript and metabolite level diverges during two different stress conditions.
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| 46. |
- Larsson, Kristina A. E., et al.
(författare)
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N-Methyltransferase involved in gramine biosynthesis in barley : Cloning and characterization
- 2006
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 67:18, s. 2002-2008
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Tidskriftsartikel (refereegranskat)abstract
- The indole alkaloid gramine occurs in leaves of certain barley (Hordeum vulgare L.) cultivars but not in others. A gene sequence in barley that earlier was characterized as a jasmonate-induced O-methyltransferase (MT) (EC 2.1.1.6, GenBank accession U54767) was here found to be absent in some barley cultivars and breeding lines that all lacked gramine. The cDNA was cloned and expressed in Escherichia coli and the recombinant protein purified. The purified recombinant protein methylated two substrates in the pathway to gramine: 3-aminomethylindole (AMI) and N-methyl-3-aminomethylindole (MAMI) at a high rate, with Km-values of 77 mu M and 184 mu M, respectively. In contrast, the protein did not exhibit any detectable methylation with the earlier suggested substrate for O-methylation, caffeic acid. A number of cultivars and breeding lines of barley were analyzed for presence of the U54767 gene sequence and NIT protein and the enzyme activity in vitro with MAMI or caffeic acid as substrates. The results showed a clear relationship between the presence of the MT gene, the NIT protein and N-methyltransferase activity, and confirmed the identification of the gene as coding for an N-methyltransferase (NMT, EC 2.1.1) and being involved in gramine biosynthesis.
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| 47. |
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| 48. |
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| 49. |
- Losvik, Aleksandra, 1985-
(författare)
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Barley defense genes against aphids
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aphids are insect pests with major importance worldwide. By feeding from plant phloem, they directly withdraw nutrients. The feeding injury is often visible in the form of leaf rolling, chlorosis, necrosis or plant deformation. Their pest status is attributed also to vectoring of plant viruses. Aphid infestation on crop plants is currently managed with the use of pesticides, which may pose a threat to the environment. An alternative approach would be to identify and characterize genetic factors contributing to aphid resistance, as well as agents inducing resistance, with the intention to use this knowledge in breeding programs.The aim of this thesis was to identify such resistance genes and characterize their involvement in plant-aphid interactions. This was accomplished using two approaches. Firstly, two putative aphid-resistance genes from barley, CI2c encoding a chymotrypsin inhibitor and LOX2.2 encoding a lipoxygenase, were transformed into Arabidopsis and/or barley and the effects of transformation were studied with regard to the performance of two aphid species. One was the specialist bird cherry-oat aphid (Rhopalosiphum padi L.), which is a pest on major cereals, and the other was a generalist, the green peach aphid (Myzus persicae Sulzer), which is a pest on plants belonging to more than 40 families. The effects of transformation were also studied concerning effects on the expression of other defense-related genes in the transgenic plants. Secondly, the effects of plant treatment with volatiles were studied with regard to induction of plant resistance, followed by tests with bird cherry-oat aphid on the treated plants.The study of overexpression of CI2c showed that the gene product transiently reduced green peach aphid fecundity on transgenic Arabidopsis, but indirectly decreased this aphid’s avoidance of barley by suppressing defense. The transformation had no effects on bird cherry-oat aphids’ behaviour or fecundity. Overexpression of LOX2.2 was shown to affect expression of other genes regulated by jasmonic acid and decreased the short-term fecundity of both the bird cherry-oat aphid and the green peach aphid on barley. The study of volatile treatments supported the idea that resistance against aphids can be induced by application of volatiles. Several defense gene sequences were induced by application of methyl salicylate, methyl jasmonate and (Z)-3-hexen-1-ol. Of the three volatiles tested, methyl jasmonate showed the greatest potential as inducing agent, causing a short-term reduction in aphid fecundity.To conclude, this thesis supports the ideas that the barley genes CI2c and LOX2.2 play a role in resistance against aphids and that moderate aphid resistance can be induced by external factors. Aphids may be directly affected by the gene product or there may be an indirect effect, caused by changes in the expression of other genes involved in plant defense. The observed negative effects on aphids were of moderate magnitude and it is proposed that acting individually, those genes are not likely to cause a strong negative effect, but they may contribute to provide resistance to aphids.
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- Losvik, Aleksandra, 1985-, et al.
(författare)
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Effects of treatments of barley with methyl salicylate, methyl jasmonate or (Z)-3-hexen-1-ol on barley gene expression and fecundity of bird cherry-oat aphid
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Aphids are serious pests on crop plants. Chemical control is currently the most efficient and widely used method to control aphid populations; however it has negative environmental consequences. Inducing aphid resistance in plants by volatile treatments may be an alternative, less harmful measure. Here, we have studied volatile induced responses in barley (Hordeum vulgare L.) and their effect on bird cherry-oat aphid (Rhopalosiphum padi L.). Barley cultivars Scandium, Lina and Barke were exposed to methyl salicylate, methyl jasmonate or (Z)-3-hexen-1-ol, plant volatiles which all have been shown to induce arthropod resistance. Treated plants were analyzed for changes in gene expression using RT-qPCR method, with focus on genes related to plant defense. Genes encoding a calcium-binding EF-hand protein, a protease inhibitor and lipoxygenase 2.2 were induced by exposure to methyl salicylate. Methyl jasmonate and (Z)-3-hexen-1-ol treatments were found to up-regulate an allene oxide synthase gene and lipoxygenase 2.1. Methyl salicylate treatment prolonged the pre-reproductive period and reduced the intrinsic rate of aphid population increase on cultivar Scandium, but had no effect on fecundity. Treatments with methyl jasmonate reduced aphid fecundity over a seven day period on two out of three tested cultivars. We did not observe any effects of methyl salicylate or methyl jasmonate treatments on aphid life span or total offspring during the life. In conclusion, we have demonstrated that all tested volatiles induce putative defense related genes, but only methyl jasmonate showed potential for protecting barley against aphids.
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