The physical, genetic, and social priorities of dynamic plant mitochondria

Chustecki, Joanna Mary ORCID: 0000-0002-1473-8415 (2022). The physical, genetic, and social priorities of dynamic plant mitochondria. University of Birmingham. Ph.D.

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Abstract

Mitochondria are key energy providers of eukaryotic cells. They are dynamic organelles and, within plants, exist in a fragmented, individual state. Mitochondrial function and positioning is vital for energy provision, metabolite exchange, proteostasis and genetic stability. Previous work has characterised plant mitochondrial motion, as well as connectivity of mitochondria in other kingdoms, but how these dynamics benefit the cell and organism remain poorly understood. Within this thesis, the physical, genetic, and ''social'' priorities of these organelle dynamics are explored, and we investigate why the plant cell controls its bioenergetic organelles in this way. Physical priorities encompass how mitochondria move, positioning within the cell and interactions with other organelles. In plants, there has not yet been a broad analysis of the entire cellular mitochondrial population and the connectivity across it. Here, connectivity between these individual organelles is quantified using a ''social'' paradigm- used to describe mitochondria as individual entities capable of communicating, and networks of encounters between these individuals are demonstrated. Genetic priorities stem from each mitochondrion harbouring its own genomic material, that within plant mitochondria is recombinatorally active- it can be rearranged, swapped and fragmented, and can be transferred between individual mitochondria, opening the question of how genetic priorities may be shaped by the physical dynamics of these organelles.

Using imaging, modelling and molecular biology approaches, we quantify physical characteristics and close encounters of mitochondria in single Arabidopsis thaliana cells to build social networks, revealing a trade-off between social connectivity and even cellular spread. We also investigate the physical-genetic link between sharing and spacing of these organelles within the cell using two fluorescent mutant lines, mtGFP-friendly and mtGFP-msh1, showing that amongst other effects, disrupted recombination surveillance of the mitochondrial genome shifts this trade-off towards increased connectivity. The unique genetic dynamics of plant mitochondria impact upon the health of the chondriome and the successive generations, and we look for evidence of mitochondrial genome recombination ability correlating with long life span across the eukaryotic tree of life. Together, the evidence put forwards demonstrates the importance of the motility and connectivity of the mitochondrial population, and its impact upon genetic stability both within plants and broader eukaryotes.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):