Mitochondria are ubiquitous eukaryotic organelles which carry out a range ofessential functions, most notably the production of ATP through the processof oxidative phosphorylation. While the main biochemical function ofmitochondria was established over 50 years ago, the processes whichcontrol mitochondrial morphology are, at present, poorly understood. Thethesis aims to add to our knowledge of the factors that control mitochondrialmorphology and dynamics in the model plant species, Arabidopsis thaliana.The phenotypic characteristics of two novel mitochondrial morphologymutants, motley mitochondria I (mmtl) and network mitochondria (nmt),were examined and quantified. mmtl has an increased heterogeneity ofmitochondrial plan area relative to wild-type, which is matched by a similarchloroplast phenotype. nmt exhibits a reticular mitochondrial morphology,similar to the mitochondria found in yeast and animals. Genetic mapping ofthe two mutant loci has established that mmtl resides on a short region ofchromosome 11w, hile nmt was mapped to a small area of chromosome V.This thesis describes the identification and functional analysis of twonovel orthologs of yeast and animal mitochondrial division genes. Using TDNAreverse genetics, it is shown that disruption of the dynamin-like DRP3Aor BIGYIN (an Arabidopsis orthologue of yeast FISI) led to an increase inmitochondrial plan area, which is coupled with a decrease in the number ofphysically discrete mitochondria per cell.Finally, the morphology and behaviour of Arabiclopsis mitochondria isinvestigated upon the induction of cell death. Abiotic stress treatments thatinduce cell death led to fast and irreversible changes in mitochondrialmorphology. The role of these changes, as possible early indicators of celldeath, are discussed.
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The control of mitochondrial morphology and dynamics in Arabidopis thaliana
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