Biology subjects

Camus, F.

Publications and source records attributed to Camus, F..

3 recordsLinked to original sources

bioRxiv2023

Assessing the role of mitonuclear interactions on mitochondrial function and organismal fitness in natural Drosophila populations

Mitochondrial metabolism is regulated by a series of enzyme complexes, whose function depends on effective interactions between proteins and RNA encoded by the mitochondrial and nuclear genomes. These epistatic interactions are in turn highly sensitive to the environment. Many studies have found that mitochondrial haplotype frequencies of various taxa associate with latitude or altitude, leading to the hypothesis that mitochondrial genomes may respond to thermal selection and contribute to local adaptation. We used a Drosophila melanogaster panel comprising native (coadapted) populations from the extremes of the Australian east-coast cline, and generated mitonuclear cybrid populations. Our results indicate a strong phenotypic impact of mitonuclear interactions in cybrid lines, involving an apparent trade-off between aerobic capacity and key fitness aspects such as reproduction, growth, and survival. Overall, our study shows that naturally-occurring mitonuclear disruptions can have a meaningful impact on phenotypes, potentially influencing future ecological adaptation and population persistence.

evolutionary biology↗

bioRxiv2021

Positive selection on mitochondria may eliminate heritable microbes from arthropod populations.

The majority of arthropod species carry facultative heritable microbes, bacteria that are passed from mother to offspring, and which may contribute to host function. These symbionts are coinherited down the maternal line with mitochondria, and selection favouring either new symbionts, or new symbiont variants, is known to drive loss of mitochondrial diversity as a correlated response. More recently, evidence has accumulated of episodic directional selection on mitochondria. We therefore examined the reciprocal interaction and model the impact of selection on mitochondrial DNA (mtDNA) on symbiont frequency. We performed this for three generic scenarios: a fixed benefit to the host carrying the symbiont, a benefit that decreased with symbiont frequency, and a benefit that increased with symbiont frequency. We find that direct selection on mtDNA can drive symbionts out of the population under some circumstances. Symbiont extinction occurs where the positively selected mtDNA mutation occurs initially in an individual that is uninfected with the symbiont, and the symbiont is initially at low frequency. When, in contrast, the positively selected mtDNA mutation occurs in a symbiont infected individual, the mutation becomes fixed and in doing so removes symbiont variation from the population. Given low frequency symbiont infections are common in natural populations, and selection on mtDNA is also considered to occur frequently, we conclude that mtDNA driven loss of symbionts represents a novel mechanism driving loss of facultative heritable microbes. We conclude further that the molecular evolution of symbionts and mitochondria, which has previously been viewed from a perspective of selection on symbionts driving the evolution of a neutral mtDNA marker, should be reappraised in the light of positive selection on mtDNA. Where low mtDNA and symbiont genetic diversity are observed, it should not be assumed to be a consequences of selection acting on the symbiont.

evolutionary biology↗

bioRxiv2017

Experimental evidence that thermal selection has shaped the latitudinal distribution of mitochondrial haplotypes in Australian fruit flies

Cellular metabolism is regulated by enzyme complexes within the mitochondrion, the function of which are sensitive to the prevailing temperature. Such thermal sensitivity, coupled with the observation that population frequencies of mitochondrial haplotypes tend to associate with latitude, altitude or climatic regions across species distributions, led to the hypothesis that thermal selection has played a role in shaping standing variation in the mitochondrial DNA (mtDNA) sequence. This hypothesis, however, remains controversial, and requires evidence that the distribution of haplotypes observed in nature corresponds with the capacity of these haplotypes to confer differences in thermal tolerance. Specifically, haplotypes predominating in tropical climates are predicted to encode increased tolerance to heat stress, but decreased tolerance to cold stress. We present direct evidence for these predictions, using mtDNA haplotypes sampled from the Australian distribution of Drosophila melanogaster. We show that the ability of flies to tolerate extreme thermal challenges is affected by sequence variation across mtDNA haplotypes, and that the thermal performance associated with each haplotype corresponds with its latitudinal prevalence. The haplotype that predominates at low (subtropical) latitudes confers greater resilience to heat stress, but lower resilience to cold stress, than haplotypes predominating at higher (temperate) latitudes. We explore molecular mechanisms that might underlie these responses, presenting evidence that the effects are in part regulated by SNPs that do not change the protein sequence. Our findings suggest that standing variation in the mitochondrial genome can be shaped by thermal selection, and could therefore contribute to evolutionary adaptation under climatic stress.

evolutionary biology↗