Interactions between temperature, mitochondrial genes and nuclear genes
affect development times in seed beetles
Katia Chavez Abiega
Mitochondria are the cellular organelles responsible for the production of up to 90% of the
energy our cells need to function. Mitochondria have their own genome (separate from the
nuclear genome located in the nucleus of the cell) referred to as the mitochondrial genome. Since
the relationship between the mitochondrial and nuclear genome coordinates metabolic energy
production, there is potential for natural selection to act upon this interaction.
There is evidence indicating that there is substantial sequence polymorphism in mitochondrial
genes, and that this variation in mitochondrial genes may result in differences in energy
production and, therefore, in fitness components, such as egg-to-adult development times.
Moreover, recent work suggests that there may be an environmental component to the outcome of
such fitness interactions between mitochondrial and nuclear genes. Here I assess the influence of
temperature, nuclear and mitochondrial genes on egg-to-adult development time in seed beetles,
Callosobruchus maculatus. In order to disentangle the effects of each genome on development
times, I utilized 25 lines of beetles carrying orthogonal combinations of distinct nuclear and
mitochondrial genes. I then tested whether or not there are differences in development times for
the beetles of each line when reared at two different temperature treatments. I found that
interactions between mitochondrial and nuclear genes affected development times, and an effect
of temperature was also found. These results suggest that mitochondrial genomes may have
differential fitness according to the nuclear background in which they are expressed and also the
temperature that they are exposed to. These results are consistent with the hypothesis that
mitochondrial genes can adapt to the thermal environment through natural selection.
Degree project in biologi
Examensarbete i biologi, 20 p, Uppsala Universitet, vår 2006
Biology Education Center and Department of Ecology and Evolution, Uppsala University
Supervisor: Damian K. Dowling, Göran Arnqvist