Dissecting functions of members of beta-oxidation multi-gene families in Arabidopsis

Andrew Wiszniewski

Research output: ThesisDoctoral Thesis

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Abstract

[Truncated abstract] In plants the catabolism of fatty-acids occurs via peroxisomal β-oxidation by the cleavage of acetyl-CoA from an acyl-CoA chain. β-oxidation is responsible for the metabolism of storage lipids during germination and membrane lipids during senescence. Additionally, the synthesis of auxin and jasmonic acid occurs via this pathway. This thesis describes research in which Arabidopsis mutants disrupted in β-oxidation enzymes were screened for classical β-oxidation phenotypes. These phenotypes included sucrose dependence for seedling establishment in the absence of storage lipid breakdown, and resistance to the auxin precursors IBA and 2,4-DB, which are metabolised to their active form by β-oxidation. As a result two enzymes, acyl activating enzyme 18 (AAE18) and short-chain dehydrogenase A (SDRA) were identified as required for response to auxin precursors. The sdra mutants were resistant to the auxin precursors 2,4-DB and IBA, while aae18 mutants were resistant only to 2,4-DB. Neither of the mutants was sucrose-dependent, and the sdra mutant had a similar fatty-acid profile to wild-type during germination. GFP-tagged SDRA and AAE18 localised to the peroxisome. A detailed characterisation of the 3-ketoacyl-thiolase (KAT) family in Arabidopsis was also instigated. In the last-step of the β-oxidation cycle the KAT enzyme catalyses the cleavage of acetyl-CoA. In Arabidopsis KAT2 is the major peroxisomal thiolase involved in the metabolism of many fatty-acid compounds including storage lipids, auxin, jasmonic acid, and membrane lipids. While KAT1 displays low constitutive expression, KAT5 is up-regulated in flowers and siliques. Additionally, the KAT5 gene encodes two isoforms, the cytosolic KAT5.1 and the peroxisomal KAT5.2. In this part of the project, detailed gene expression analysis was conducted using promoter-GUS-reporter and qRT-PCR experiments.
Original languageEnglish
QualificationDoctor of Philosophy
Publication statusUnpublished - 2011

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