The role of very long chain fatty acids in Arabidopsis growth and development

• Main Author: Seamons, Laura Elizabeth
• Published: University of Nottingham 2015
• Subjects: 583; QP501 Animal biochemistry
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664692

Very long chain fatty acids (VLCFAs) are essential to Arabidopsis growth and development. VLCFAs are found in sphingolipids, glycerophospholipids, triacylglycerols, suberin and cuticular waxes. VLCFAs are synthesized by the addition of 2 carbons from malonyl-CoA to pre-existing acyl-CoAs to produce chain lengths of greater than 18 carbon atoms. VLCFA synthesis involves four consecutive reactions that are catalysed by the microsomal Fatty Acid Elongase. In Arabidopsis the first reaction is catalysed by one of 21 different Keto-CoA Synthases (KCS) with diverse levels of expression and overlapping tissue specificities. The other three enzymes are ubiquitously expressed throughout the plant, and form the core components of the elongase. Lipidomic profiling has been performed on roots and shoots of plants with reduced levels of VLCFAs. Mutants of the core components of the elongase were analysed along with herbicides that inhibit a number of KCS enzymes, this allowed the whole elongase complex to be analysed. Differences were seen in the lipidomic profiles of the different elongase mutants and between the roots and shoots of the same mutants. This has revealed correlations between phenotypic differences and lipidomic changes giving insight into which lipid classes might be responsible for the various phenotypes. A forward genetic screen has been conducted in the Arabidopsis cer10-1 mutant to identify novel genes involved in VLCFA metabolism. CER10 encodes for the fourth component of the elongase complex. One suppressor mutant that has been identified has flower buds and fertility comparable to wild type plants but still displays the reduced size of the cer10-1 mutant. The second suppressor mutant identified showed restored size of aerial organs but the flower buds remained fused. Whole genome sequencing allowed localisation of these suppressor mutations on Chromosome 3. Partial biochemical characterisation of these mutants revealed interesting changes in their acyl-CoA and cuticular lipid profiles.