The control of mitochondrial morphology and dynamics in Arabidopis thaliana
Abstract
Mitochondria are ubiquitous eukaryotic organelles which carry out a range of
essential functions, most notably the production of ATP through the process
of oxidative phosphorylation. While the main biochemical function of
mitochondria was established over 50 years ago, the processes which
control mitochondrial morphology are, at present, poorly understood. The
thesis aims to add to our knowledge of the factors that control mitochondrial
morphology and dynamics in the model plant species, Arabidopsis thaliana.
The phenotypic characteristics of two novel mitochondrial morphology
mutants, motley mitochondria I (mmtl) and network mitochondria (nmt),
were examined and quantified. mmtl has an increased heterogeneity of
mitochondrial plan area relative to wild-type, which is matched by a similar
chloroplast phenotype. nmt exhibits a reticular mitochondrial morphology,
similar to the mitochondria found in yeast and animals. Genetic mapping of
the two mutant loci has established that mmtl resides on a short region of
chromosome 11w, hile nmt was mapped to a small area of chromosome V.
This thesis describes the identification and functional analysis of two
novel orthologs of yeast and animal mitochondrial division genes. Using TDNA
reverse genetics, it is shown that disruption of the dynamin-like DRP3A
or BIGYIN (an Arabidopsis orthologue of yeast FISI) led to an increase in
mitochondrial plan area, which is coupled with a decrease in the number of
physically discrete mitochondria per cell.
Finally, the morphology and behaviour of Arabiclopsis mitochondria is
investigated upon the induction of cell death. Abiotic stress treatments that
induce cell death led to fast and irreversible changes in mitochondrial
morphology. The role of these changes, as possible early indicators of cell
death, are discussed.
Type
Thesis, PhD Doctor of Philosophy
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