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- Frenkel, Martin, et al.
(författare)
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Improper excess light energy dissipation in Arabidopsis results in a metabolic reprogramming
- 2009
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Ingår i: BMC Plant Biology. - : Springer Science and Business Media LLC. - 1471-2229. ; 9:12, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Background: Plant performance is affected by the level of expression of PsbS, a key photoprotective protein involved in the process of feedback de-excitation (FDE), or the qE component of non-photochemical quenching, NPQ. Results: In studies presented here, under constant laboratory conditions the metabolite profiles of leaves of wild-type Arabidopsis thaliana and plants lacking or overexpressing PsbS were very similar, but under natural conditions their differences in levels of PsbS expression were associated with major changes in metabolite profiles. Some carbohydrates and amino acids differed ten-fold in abundance between PsbS-lacking mutants and over-expressers, with wild-type plants having intermediate amounts, showing that a metabolic shift had occurred. The transcriptomes of the genotypes also varied under field conditions, and the genes induced in plants lacking PsbS were similar to those reportedly induced in plants exposed to ozone stress or treated with methyl jasmonate (MeJA). Genes involved in the biosynthesis of JA were up-regulated, and enzymes involved in this pathway accumulated. JA levels in the undamaged leaves of field-grown plants did not differ between wild-type and PsbS-lacking mutants, but they were higher in the mutants when they were exposed to herbivory. Conclusion: These findings suggest that lack of FDE results in increased photooxidative stress in the chloroplasts of Arabidopsis plants grown in the field, which elicits a response at the transcriptome level, causing a redirection of metabolism from growth towards defence that resembles a MeJA/JA response.
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| 2. |
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| 3. |
- Frenkel, Martin, et al.
(författare)
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An illustrated gardener's guide to transgenic Arabidopsis field experiments
- 2008
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 180:2, s. 545-555
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Tidskriftsartikel (refereegranskat)abstract
- Field studies with transgenic Arabidopsislines have been performed over 8 yr, to better understand the influence that certain genes have on plant performance. Many (if not most) plant phenotypes cannot be observed under the near constant, low-stress conditions in growth chambers, making field experiments necessary. However, there are challenges in performing such experiments: permission must be obtained and regulations obeyed, the profound influence of uncontrollable biotic and abiotic factors has to be considered, and experimental design has to be strictly controlled. The aim here is to provide inspiration and guidelines for researchers who are not used to setting up such experiments, allowing others to learn from our mistakes. This is believed to be the first example of a ‘manual’ for field experiments with transgenic Arabidopsisplants. Many of the challenges encountered are common for all field experiments, and many researchers from ecological backgrounds are skilled in such methods. There is huge potential in combining the detailed mechanistic understanding of molecular biologists with ecologists’ expertise in examining plant performance under field conditions, and it is suggested that more interdisciplinary collaborations will open up new scientific avenues to aid analyses of the roles of genetic and physiological variation in natural systems.
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| 4. |
- Frenkel, Martin, 1973-
(författare)
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Light, stress and herbivory : from photoprotection to trophic interactions using Arabidopsis thaliana as a model organism
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Photosynthesis is the most important process for nearly all life on earth. Photosynthetic organisms capture and transfer light energy from the sun into chemical energy which in turn provides a resource base for heterotrophic organisms. Natural light regimes are irregular and vary over magnitudes. At a certain light intensity, metabolic processes cannot keep up with the electron flow produced by the primary photoreactions, and thus reactive oxygen species (ROS) are produced. ROS are highly reactive and can damage the photosynthesis apparatus and hence plants have evolved several photoprotection mechanisms to avoid the formation of ROS. The aim of this thesis was to examine the ecological effects of variations in photoprotection in plants. In particular I wanted to study the effect on fitness and the interaction with herbivorous insects of plants with different ability in photoprotection. To study this I used wild-type and transgenic Arabidopsis thaliana plants and grew them under natural conditions in field experiments in our botanical garden in Umeå, northern Sweden. For the investigation of the plant-insect interaction, a specialist on Brassicaceae (Plutella xylostella – diamondback moth) and a generalist herbivore (Spodoptera littoralis - Egyptian cotton worm) were used. Plants that are genetically deficient in one of the photoprotection mechanisms showed reduced fitness under natural conditions. I could thus show that feedback de-excitation (FDE) is the most important photoprotection mechanism, because a lack of FDE showed the highest reduction in fitness. The comparison of field grown wild-type with FDE mutant plants, using molecular biology methods, revealed large changes in gene transcription and metabolic composition. In particular, the jasmonate pathway was upregulated in light stressed plants, especially in plants lacking FDE. Jasmonate in turn is known to be a chemical compound which induces herbivore resistance genes and other stress responses. Specialist and generalist insect herbivores responded differently in feeding (dual-choice and no-choice) and oviposition experiments with field grown plants that differed in FDE. Female diamondback moths were attracted by induced defense compounds whereas the larvae avoided these plants in feeding experiments. Generalist larvae preferred, and showed a higher survival rate, on less light-stressed plants compared to more light-stressed plants. Combining molecular biology with ecological experiments is a challenging task. To summarize my experiences, I have produced a guide for experiments on transgenic plants in common gardens. In future investigations it is important to examine natural variations in photoprotection to elucidate selection pressures on specific genes.
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| 5. |
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| 6. |
- Johansson Jänkänpää, Hanna, 1981-, et al.
(författare)
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Arabidopsis thaliana with reduced capacity for non-photochemical quenching show altered herbivore preference
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Under natural conditions, plants have to cope with a multitude of stresses, two of those are light-stress and herbivory. Plants have evolved several mechanisms to avoid the damage done by strong and fluctuating light and one important photoprotection mechanism is the qE-type of non-photochemical quenching (NPQ) where the PsbS protein is involved. We have compared Arabidopsis thaliana wild type and two "photoprotection genotypes", npq4 and oePsbS that, respectively, lack and overexpress PsbS. In dual-choice feeding experiments on field-grown plants with a specialist (Plutella xylostella) and a generalist (Spodoptera littoralis) insect herbivore, both herbivores preferred the plants with higher expression of PsbS. Also both herbivores survived equally well on the different genotypes but for oviposition, female adults of Plutella xylostella preferred plants with lower expression of PsbS. No difference in the amount and composition of the ten most prominent glucosinolates — the most important substances in the Arabidopsis chemical warfare against herbivores — were found between the genotypes. When leaves of the three genotypes, after transfer from a growth chamber to the field, were profiled for changes in composition of metabolites using GC-MS, we found significant differences in metabolite composition. This suggests that differences in herbivore preferences were rather a consequence of changes in the primary metabolism of the plant rather than differences in the composition of typical "defence compounds". In npq4, superoxide accumulated under high light conditions and is likely to directly, or indirectly after dismutation to H2O2, trigger the metabolic change.
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| 7. |
- Johansson Jänkänpää, Hanna, et al.
(författare)
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Non-photochemical quenching capacity in arabidopsis thaliana affects herbivore behaviour
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:1, s. e53232-
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Tidskriftsartikel (refereegranskat)abstract
- Under natural conditions, plants have to cope with numerous stresses, including light-stress and herbivory. This raises intriguing questions regarding possible trade-offs between stress defences and growth. As part of a program designed to address these questions we have compared herbivory defences and damage in wild type Arabidopsis thaliana and two "photoprotection genotypes", npq4 and oePsbS, which respectively lack and overexpress PsbS (a protein that plays a key role in qE-type non-photochemical quenching). In dual-choice feeding experiments both a specialist (Plutella xylostella) and a generalist (Spodoptera littoralis) insect herbivore preferred plants that expressed PsbS most strongly. In contrast, although both herbivores survived equally well on each of the genotypes, for oviposition female P. xylostella adults preferred plants that expressed PsbS least strongly. However, there were no significant differences between the genotypes in levels of the 10 most prominent glucosinolates; key substances in the Arabidopsis anti-herbivore chemical defence arsenal. After transfer from a growth chamber to the field we detected significant differences in the genotypes' metabolomic profiles at all tested time points, using GC-MS, but no consistent "metabolic signature'' for the lack of PsbS. These findings suggest that the observed differences in herbivore preferences were due to differences in the primary metabolism of the plants rather than their contents of typical "defence compounds". A potentially significant factor is that superoxide accumulated most rapidly and to the highest levels under high light conditions in npq4 mutants. This could trigger changes in planta that are sensed by herbivores either directly or indirectly, following its dismutation to H2O2.
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