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Light, stress and herbivory: from photoprotection to trophic interactions using Arabidopsis thaliana as a model organism
Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Umeå: Ekologi, miljö och geovetenskap , 2008. , 23 p.
Keyword [en]
Arabidopsis thaliana, photoprotection, herbivory, light-stress, jasmonate, fitness, FDE, dual-choice
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:umu:diva-1651ISBN: 978-91-7264-643-1 OAI: oai:DiVA.org:umu-1651DiVA: diva2:141710
Public defence
2008-06-04, Lilla hörsalen, KBC-huset, Umeå University, 901 87 Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2008-05-13 Created: 2008-05-13 Last updated: 2009-06-22Bibliographically approved
List of papers
1. Hierarchy amongst photosynthetic acclimation responses for plant fitness
Open this publication in new window or tab >>Hierarchy amongst photosynthetic acclimation responses for plant fitness
2007 (English)In: Physiologia Plantarum, Vol. 129, no 2, 455-459 p.Article in journal (Refereed) Published
Abstract [en]

We have compared the seed production of Arabidopsis wild-type and mutant plants impaired in the regulation of the photosynthetic light reactions grown under natural conditions in the field. Mutant plants (npq4) lacking feedback de-excitation were, as previously demonstrated, severely affected in seed production. Seed sets of plants deficient in state transitions (stn7) were 19% smaller than those of wild-type plants, whereas plants missing the STN8 kinase required for the phosphorylation of the core photosystem II reaction centre polypeptides (stn8) had a normal seed production. Plants lacking both STN7 and STN8 kinases were strongly affected, indicating that these mutations act synergistically. In contrast, npq4×stn7 double mutants had the same seed set as npq4 mutants.

Identifiers
urn:nbn:se:umu:diva-11881 (URN)doi:10.1111/j.1399-3054.2006.00831.x (DOI)
Available from: 2007-04-16 Created: 2007-04-16 Last updated: 2015-04-29Bibliographically approved
2. Improper regulation of light harvesting in Arabidopsis results in a metabolic reprogramming
Open this publication in new window or tab >>Improper regulation of light harvesting in Arabidopsis results in a metabolic reprogramming
Show others...
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
Identifiers
urn:nbn:se:umu:diva-3206 (URN)
Available from: 2008-05-13 Created: 2008-05-13 Last updated: 2015-04-29Bibliographically approved
3. Plant photoprotection influences herbivore preferences
Open this publication in new window or tab >>Plant photoprotection influences herbivore preferences
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
Identifiers
urn:nbn:se:umu:diva-3207 (URN)
Available from: 2008-05-13 Created: 2008-05-13 Last updated: 2015-04-29Bibliographically approved
4. An illustrated gardener's guide to transgenic Arabidopsis field experiments
Open this publication in new window or tab >>An illustrated gardener's guide to transgenic Arabidopsis field experiments
2008 (English)In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 180, no 2, 545-555 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
Arabidopsis thaliana, field experiments, fitness, herbivory, transgenic lines, variation
National Category
Botany
Research subject
Physiological Botany
Identifiers
urn:nbn:se:umu:diva-3208 (URN)10.1111/j.1469-8137.2008.02591.x (DOI)18721164 (PubMedID)
Available from: 2008-05-13 Created: 2008-05-13 Last updated: 2017-12-14Bibliographically approved

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