In plants the effective partitioning of carbon and nitrogen assimilates between source and sink tissues is essential for growth and development. The regulation of sugar transporters is pivotal not only to the allocation of carbohydrates throughout the plant but in providing sugars, which may act as signals in the modulation of gene expression. Many of the genes associated with the production, distribution, utilisation and storage of assimilates are regulated by sugars. The <i>Arabidopsis thaliana</i> Sugar Transport Protein 1 (AtSTP1) is the principal monosaccharide transporter in <i>Arabidopsis </i>seedlings, accounting for approximately 60% of 3-O-methyl glucose uptake activity. Characterisation of <i>AtSTP1</i> gene expression and transport activity <i>in vitro</i> in plantlets growth in continuous light and in a diurnal growth regime reveal regulation in light, glucose and mechanical stimulation. A rapid accumulation of <i>AtSTP1</i> transcripts upon transfer to the dark was observed in all growth regimes tested. This appears to be a novel feature in sugar transporter regulation. In light grown plantlets, dark-induced <i>AtSTP1</i> transcripts diminished within 1 h of subsequent treatment with exogenous 3 mM D-glucose or white light. Furthermore, a 5 min pulse of white light resulted in a marked repression of dark-induced <i>AtSTP1 </i>transcripts, which is indicative of sugar-independent regulation. The diurnal regulation of the <i>AtSTP1 </i>gene in plantlets entrained a L12 h:D12 h regime is complex, as is the subsequent <i>AtSTP1 </i>response to sugars. The expression pattern of the <i>AtSTP1 </i>gene was different in the shoot and roots; furthermore in the shoots <i>AtSTP1 </i>transcripts displayed circadian rhythm upon transfer to continuous light. It appears that at least three signalling pathways interact in the regulation of STP1 synthesis and activity in <i>Arabidopsis thaliana. </i>These results are discussed in terms of the possible physiological functions of AtSTP1, including retrieval of sugars derived from the cell wall.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:640367 |
| Date | January 2002 |
| Creators | Alford, Heather Lynne |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/11043 |
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