Mitochondrial genes matter

Jan 14, 2014 by Linda Koffmar
Mitochondrial genes matter!
The researchers followed 180 populations of the seed beetle Callosobruchus maculatus for more than 10 generations. Credit: Göran Arnqvist

Contrary to common belief, mitochondrial genes seem to matter for how well individuals survive and reproduce. These new results are reported by researchers at Uppsala University, Sweden, who studied the genes of a common beetle species.

Mitochondria are vital power plants of cells. They carry their own genes, which are inherited only through females, and these genes vary greatly between individuals. In the latest issue of the prestigious scientific journal Ecology Letters, researchers from Uppsala University show for the first time that differences in the that individuals carry actually affect how well they survive and reproduce.

It took the researchers two years to conduct the experiments, where they followed 180 populations of the seed beetle Callosobruchus maculatus for more than 10 generations. The results are based on gene sequence data from more than 2000 individuals.

Remarkably, the authors found that individuals who carried rare mitochondrial genes were consistently those who did best.

"This provides an explanation for why genetic variation is maintained. Much like a pendulum of a clock will never stop in either of the extreme sideway positions", says Professor Göran Arnqvist, one of the authors of the study.

For decades, much biological research has rested on the assumption that different variants of the same mitochondrial gene are equivalent in terms of function of the gene. These genes have therefore been extensively used as a neutral "markers" that allow, for example, determination the size of populations or reconstructions of the history of immigration into an area. The authors of the new study point out that this usage is very problematic indeed if different versions of the same mitochondrial gene are not functionally equivalent.

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More information: Erem Kazancıoglu, Göran Arnqvist, The maintenance of mitochondrial genetic variation by negative frequency-dependent selection, Ecology Letters (2014) 17: 22–27, doi: 10.1111/ele.12195

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1 / 5 (1) Jan 14, 2014
Contrary to common belief

What idiot held the common belief that genes don't matter in mitochondria?

First of all, that's just plain stupid, as if they'd do their job without the genes; couldn't survive at all.

Secondly, that claim contradicts the theory of "endo-symbiosis," which however unlikely, is supposedly the prevailing theory in cell biology for the origin of Mitochondria. Obviously if the Mitochondria are supposedly descended from another single-celled organism which was engulfed by the main cell, then the Mitochondria's DNA and genes certainly do matter. Either way, because of the first point above, the genes obviously matter.
1 / 5 (2) Jan 14, 2014
The authors of the new study point out that this usage is very problematic indeed if different versions of the same mitochondrial gene are not functionally equivalent.

This is the problem with Darwinian evolution. When you change the length or content of a "code", be it chemical or electronic or some other means, you in fact change what it does. If you change it significantly enough, for example replacing Cysteine with some other amino acid, then not only do you change primary structure of the resulting protein, but you also dramatically change secondary, tertiary, and quarternary structure, because you removed a disulfide bond. This results in an opening in the space where the disulfide bond should be, producing a different geometry and a different topology for the final shape of the protein(s).

While removing Cysteine is the most drastic one amino-acid change of which I can think, it makes the point. All it takes is a one atom difference to totally change the shape of things

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