In two feeding experiments Bacillus induced priming of plant defense was tested for its effect against the generalist insect pest Spodoptera littoralis. The main hypothesis for the study was that Bacillus induced priming would enable the plant Arabidopsis thaliana to defend itself better against this insect herbivore since this priming seems to involve jasmonic acid, known to be important for plant defense to insects. A secondary objective of the study was to examine if any differences in a primed defense capability could be seen between different natural genetic variants (ecotypes) of A. thaliana reflecting habitat differences in pest pressure. The methods used for plant cultivation and Bacillus inoculation were aimed at reflecting conditions that can be expected in an agricultural cropping system. This meant that all plants were cultivated in soil, and the feeding experiments were conducted with the plants growing intact in the soil system.

PSI-N is one of the subunits in eukaryotic Photosystem I (PSI) and is located on the lumenal side of the thylakoid membrane. It is known to interact in the electron transport chain between plastocyanin and PSI, but the mechanism behind the interaction is still unclear. To achieve a better understanding of PSI-N´s role in the photosynthesis it is necessary to develop a method for purification of PSI-N. The goal with this project was to design a plasmid that encodes a fusion protein containing PSI-N. With use of proteases the fusion protein can be cleaved into purified PSI-N.

PSI-N is one of the subunits in eukaryotic Photosystem I (PSI) and is located on the lumenal side of the thylakoid membrane. It is known to interact in the electron transport chain between plastocyanin and PSI, but the mechanism behind the interaction is still unclear. To achieve a better understanding of PSI-N´s role in the photosynthesis it is necessary to develop a method for purification of PSI-N. The goal with this project was to design a plasmid that encodes a fusion protein containing PSI-N. With use of proteases the fusion protein can be cleaved into purified PSI-N.

Plant tRNA isopentenyltransferases (tRNA-IPT, EC 2.5.1.8) have two roles, modification of tRNA and contribution to cytokinin synthesis. tRNA-IPT is among the best studied of the tRNA-modifying enzymes, but little biochemical information is available and none for the plant enzymes. Therefore two sets of experiments were conducted. The first one aimed to determine the kinetics and substrate specificity of the tRNA-IPT AtIPT2 from the higher plant Arabidopsis thaliana. The second project aimed to study the role of IPTs from the moss Physcomitrella patens in the production of cytokinin hormones.

This study has focused on testing the following two hypotheses:? Pest resistant plants have higher levels and/or several different kinds of secondary metabolites. ? Induced defensive systems in resistant plants are activated more rapidly than those of susceptible plants. As a background for the test of the hypotheses a short literature study was performed concerning plant defensive mechanisms in Arabidopsis thaliana.

This review article presents the splicing process during messenger RNA maturation and how it is regulated by different Cis-regulatory RNA-sequence elements and splicing factors. A more detailed description of the process alternative splicing and its importance to the function of genes from the model organism Arabidopsis thaliana is also given. A single eukaryotic gene can by the process alternative splicing (AS) give rise to a number of functionally mature mRNA-molecules, which in turn encodes for structurally and/or functionally different proteins. During the course of evolution, the process alternative splicing has thus shown to be effective in increasing transcriptome and proteome diversity of most eukaryotic organisms. This suggests therefore that the dominant theory in molecular biology, a gene encodes for a protein, needs to be corrected.

System based models of plants rely on descriptions and assigned functions of genes, and currently 50% of the genes in Arabidopsis thaliana has either no assigned function or a function based on homology only. Mitogen activated protein kinases (MAPK's) are key players in cell signalling and are conserved among eukaryotes, though their targets are highly diverse. A recent study has described a small Arabidopsis protein (80), without homology to any described protein, as a phosphorylation target of the MAPK's MPK3/6. Further work established ?-glucan phosphorylase (PHS) as interacting with 80 and described a delayed senescence phenotype for 80 knock-out plants.

Alternativ splicing är en process som ger upphov till att olika mRNA-sekvenser bildas från en enda gen, vilket bidrar till en ökad proteindiversitet hos organismen. Olika mRNA-sekvenser kan uppstå eftersom att det förekommer olika varianter av alternativ splicing som även kan kombineras på flera olika sätt: cassette exon (inkludering/exkludering av exon), intron retention (intronet behålls), alternative 5´splice-site choice (olika 5´ splice sites kan väljas) och slutligen alternative 3´ splice-site choice (andra 3´ splice sites kan väljas). För att alternativ splicing ska äga rum i olika pre-mRNA måste den regleras av cis-reglerande element. De cis-reglerande elementen utgörs av fyra grupper: exonic splicing enhancers (ESE), exonic splicing silencers (ESS), intronic splicing enhancers (ISE) samt intronic splicing silencers (ISS). Som namnen förtäljer finns de antingen i exoner eller introner, där de interagerar med transagerande faktorer, SR-proteiner (aktiverare) eller hnRNPs (hämmare).

Promoters are genetic elements that facilitate the transcription of a gene and they have been found in front of non-coding RNA (ncRNA) genes in different organ-isms, e.g. the model plant Arabidopsis thaliana. A similar element, DUSE, has been found in front of ncRNAs in the social amoeba Dictyostelium discoideum and a part of this project has been to analyze the function of this putative promoter element through cloning and expression studies. A construct to analyze the func-tion of DUSE was successfully designed and introduced into D. discoideum but full expression studies were not finished because of shortage of time.

Promoters are genetic elements that facilitate the transcription of a gene and they have been found in front of non-coding RNA (ncRNA) genes in different organ-isms, e.g. the model plant Arabidopsis thaliana. A similar element, DUSE, has been found in front of ncRNAs in the social amoeba Dictyostelium discoideum and a part of this project has been to analyze the function of this putative promoter element through cloning and expression studies. A construct to analyze the func-tion of DUSE was successfully designed and introduced into D. discoideum but full expression studies were not finished because of shortage of time.

Promoters are genetic elements that facilitate the transcription of a gene and they have been found in front of non-coding RNA (ncRNA) genes in different organ-isms, e.g. the model plant Arabidopsis thaliana. A similar element, DUSE, has been found in front of ncRNAs in the social amoeba Dictyostelium discoideum and a part of this project has been to analyze the function of this putative promoter element through cloning and expression studies. A construct to analyze the func-tion of DUSE was successfully designed and introduced into D. discoideum but full expression studies were not finished because of shortage of time.