This project sets out to understand further the use of the conserved DNA sequence motif CCAAT in the modulation of plant gene transcription, by the isolation and characterisation of CCAAT box binding proteins (CBP's) from the model plant <I>Arabidopsis</I>. A highly conserved CBP complex consisting of CBP2, 3 and 5 has previously been identified in a range of organisms including yeast and vertebrates. Several strategies for the isolation of <I>Arabidopsis</I> CBP homologues were attempted. Functional complementation of the yeast <I>HAP2</I> mutant identified three independent <I>Arabidopsis</I> CBP2 cDNAs. Searching the <I>Arabidopsis</I> expressed sequence tag (est) database revealed two forms each of CBP3 and CBP5. The presence of multiple forms of each CBP homologue is unusual as they are encoded by a single gene in yeast and vertebrates. These seven cDNAs were sequenced on both DNA strands and the putative protein sequence determined. Southern hybridisation gave an indication of the genomic copy number of each clone, while hybridisation of labelled cDNAs to RNA extracted from a range of tissues characterised their expression pattern. While CBP2 and CBP5 homologues were expressed equally in each tissue analysed, the two CBP3 cDNAs were preferentially expressed in aerial parts. Comparison of protein sequences with other CBPs identified conserved amino acid residues that have been shown to be of functional importance. These conserved domain sequences were also used to examine the evolutionary relationship of the multiple <I>Arabidopsis</I> forms and those from other organisms. The identification of multiple, novel forms of CBP from <I>Arabidopsis </I>is discussed in relation to their potential mode of action and role in plant development.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:598782 |
| Date | January 1997 |
| Creators | Edwards, D. B. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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