This thesis describes the analysis of the AtSTP1 protein of <i>Arabidopsis thaliana</i> with regard to its physiological role. The AtSTP1 protein is a high affinity proton monosaccharide symporter which is located within the plasmamembrane. The AtSTP1 gene is expressed in various tissues of<i> Arabidopsis</i> including stems, roots, flowers, sepals, ovaries and leaves where the AtSTP1 mRNA is most abundant. The AtSTP1 protein belongs to a gene family with at least 16 members in <i>Arabidopsis</i>. The physiological function which has been proposed for individual members of this family includes the import of monosaccharides into symplastically isolated sink cells like pollen grains, embryos and guard cells or into cells with an increased carbohydrate demand due to wounding, pathogen infection or developmental processes. A role for monosaccharide transporters as part of one sugar sensing system which controls the carbohydrate metabolism of the plant has also been proposed. In order to elucidate the biological function of the AtSTP1 protein an AtSTP1 knock-out line, a line which overexpresses the AtSTP1 gene under control of the 35S-CaMV promotor and wild type plants were analysed with regard to their ability to transport monosaccharides and phenotypic effects after feeding with monosaccharides. Feeding whole seedlings with μM concentrations of glucose showed that in the knock-out line glucose uptake is decreased by 40% whereas in the overexpressing line in a two fold increase glucose uptake is observed compared to wild type line under these conditions. When the seedlings are fed with 200 mM glucose there is no difference in the glucose concentration accumulated in the knock-out line and wild type line whereas the overexpressing line shows a significantly higher glucose content. When the plants are grown in the absence of any added monosaccharides no phenotypic differences between the knock-out line, the overexpressing line and the wild type line can be observed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:652317 |
| Date | January 2000 |
| Creators | Hemmann, Georg A. V. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12206 |
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