At the late stages of seed maturation, Arabidopsis thaliana seeds become filled with storage lipids. This source of energy is then used to support seed germination and seedling establishment. Although the metabolic pathways for synthesis and mobilisation of storage oil are well known, the regulation of these pathways remains more unclear. The aim of this project was to study the mechanisms of regulation of storage oil metabolism at the transcriptional level by identifying the transcriptional regulators and their target binding sequences in the promoters of genes involved in oil biosynthesis and breakdown in Arabidopsis seeds. A reverse genetic screen allowed the identification a transcription factor belonging to the bZIP family that is required for normal seed fatty acid composition. Seeds of the bzip67 mutant contain more linoleic (18:2) and less oleic (18:1) and linolenic (18:3) acid in their oil indicating that the desaturation process is compromised. Real-time PCR suggests that bZIP67 is a positive regulator of FATTY ACID DESATURASE 3 and a repressor of REDUCED OLEATE DESATUATION 1. Both genes are involved in fatty acid desaturation. Data from over-expression of bZIP67 also indicates that other partners are likely to be required to promote FAD3 gene expression. A different approach was taken to study the regulators of oil breakdown. Promoter analysis study of MALATE SYNTHASE (MLS) was carried out. MLS is a marker gene for the glyoxylate cycle, which allows the conversion of oil to sugar upon seed germination. Characterisation of T-DNA mutants disrupted in the MLS promoter suggests that the information required to drive MLS expression falls in the first ~140 bp of the promoter. The results show that this region is conserved in different Brassicales species and contains a number of conserved putative elements possibly required for MLS post-germinative expression. Different promoter-reporter constructs lacking each of the conserved elements were tested with a transient assay system using biolistics and the results indicate that putative ABI5, R1MYB, ABI4 and DOF binding elements are required for full MLS expression. Transcription factors from these families are therefore strong candidates as regulators of MLS expression.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:560284 |
| Date | January 2011 |
| Creators | Mendes, Ana Teresa |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/51477/ |
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