Biology subjects

Mital, A.

Publications and source records attributed to Mital, A..

4 recordsLinked to original sources

bioRxiv2025

The aging transcriptome: a condition-dependent response to a deteriorating soma

Organismal function requires precise gene expression, as deviations reduce fitness and can cause disease. The widespread expression changes characteristic of old age therefore suggests that aging itself may partly stem from gene dysregulation. Alternatively, many of these changes may represent a plastic response to somatic decline, tuning the organism to an altered physiological state. We tested the latter hypothesis by experimentally reducing the condition of Drosophila melanogaster females independently of age and comparing the resulting expression changes with those occurring naturally during aging. Consistent with the plasticity hypothesis, we find substantial overlap between genes responding to reduced condition and old age. Downregulated genes are enriched for metabolic functions, with a consistent, albeit weaker, association with mitochondrial function and cytoplasmic translation, while upregulated genes relate to genome maintenance. Both old age and reduced condition also cause downregulation of tissue-specific and female-biased genes, as expected when energy is reallocated to core cellular processes. In line with a coordinated transcriptional response to old age, both down- and upregulated genes within enriched functional categories show reduced expression variability and experience strong purifying selection. Collectively, our results support that the aging soma elicits a plastic transcriptional program that adjusts the organism to a declining physiological condition, implying that many age-related expression changes mitigate rather than accelerate somatic aging. These findings call for a more nuanced view of the causes and consequences of age-related transcriptional change, with implications for both theoretical and applied research on aging and disease.

genetics↗

bioRxiv2025

Bigger is not always better: size-dependent fitness effects of adult crowding in Drosophila melanogaster

Density-dependent selection is an important factor shaping the evolution of life histories. In holometabolous insects, crowding in the larval and adult stages can have very different effects on key fitness components. While the nuanced effects of density-dependent selection through larval crowding in Drosophila melanogaster have been extensively studied for various life history traits, very few studies have investigated the effects of adult crowding in Drosophila. Moreover, these few studies were mostly conducted on large flies, derived from low larval density cultures, and typically treated the overall density of flies per culture container as an index of the strength of adult crowding. We hypothesized that the size of the adults should shape the impact of adult crowding, with small individuals experiencing less stress than large individuals when crowded. Consequently, the adverse fitness effects usually associated with adult crowding may not be observed for small individuals. We tested this hypothesis by subjecting flies of different sizes - regular-sized flies, and small flies derived via larval crowding or selection for rapid development to adulthood - to an episode of adult crowding and examining their mortality and fecundity. Thus, we explored the interactive effects between larval and adult crowding on key fitness components. Small body size enabled flies to handle adult crowding better, with significantly lower mortality under crowded conditions when compared to flies of large body size. Moreover, small flies showed a consistent pattern of increased fecundity upon adult crowding. This positive impact on fecundity was not observed when larger flies were crowded. It is clear from our study that the effects of adult crowding can be very nuanced and body size-specific, even to the extent of having a net beneficial effect on fitness components, contrary to previous belief.

ecology↗

bioRxiv2021

Extremely rapid development and early reproduction reduces sexual selection in D. melanogaster populations.

The role of sexual selection in mediating levels of sexual conflict has been demonstrated in many experimental evolution studies on Drosophila spp. where competition among males for mating was the target of selection. Sexual selection has also been shown to affect the evolution of life-histories. However, the influence of divergent life-histories on reproductive strategies and, therefore, sexual selection and possibly sexual conflict, has been less well studied. We examined D. melanogaster populations selected for a short development time and early age at reproduction for changes in reproductive behaviour and traits that are proxies of sexual selection. We report a large reduction in reproductive competition experienced by the males of these populations, compared to ancestral populations that are not consciously selected for rapid development or early reproduction, potentially leading to reduced sexual selection. We show that rapidly developing and early reproducing populations have very low levels of mating in their lifetime (females are more or less monandrous), low courtship levels, shorter copulation duration, and longer time from eclosion to first mating, compared to the controls. These results are discussed in the context of the previously demonstrated reduction of inter-locus sexual conflict in these populations. We show that life-history strategies might have a large and significant impact on sexual selection, with each influencing the other and contributing to the complexities of adaptation. Significance statementSexual conflict, often manifested as an arms-race between males and females trying to enhance their own reproductive success at some cost to the other, is of great evolutionary interest because it can maintain genetic variation in populations, prevent the independent optimization of male and female traits, and also promote speciation. Sexual selection, or variation in mating success, is well known to affect levels of sexual conflict. However, it is not so clear whether, and how, the regular evolution of life-histories also affects sexual selection. Here, we show that life-history evolution in fruit fly populations selected for traits not directly related to sexual conflict might, nevertheless, mediate the possible evolution of altered sexual conflict levels through effects on sexual selection. Populations that evolved to develop to adulthood fast, and reproduce relatively early in life, are shown to potentially experience less sexual selection, which can explain the low sexual conflict levels earlier observed in them.

evolutionary biology↗

bioRxiv2021

Evolution of lower levels of inter-locus sexual conflict in D. melanogaster populations under strong selection for rapid development.

D. melanogaster laboratory populations subjected to selection for rapid development and early reproduction have been found to have evolved reduced adult body size and lower levels of inter-locus sexual conflict compared to their ancestral controls. We tested the contribution of a smaller body to the evolution of reduced sexual conflict in these populations, since body size differences are known to affect sexual conflict levels in this species. We cultured larvae from the control populations at high density to obtain flies as small as those from the selected populations. The effect of body size reduction on sexual conflict was asymmetric, with smaller body size resulting in reduced male manipulative ability but not female resistance to mating-induced harm. These results were not due to differences in behavioural patterns of smaller flies, such as differences in overall mating exposure of females to different types of males. We hypothesize that evolution for rapid development and the correlated reduction in body size has resulted in lower male manipulative ability, and sexually antagonistic co-evolution has lowered female resistance to such manipulations. These populations have also evolved incipient reproductive isolation from their controls, likely through sexual conflict (reported earlier), and our results support the view that this is an outcome of strong, directional selection for rapid development.

evolutionary biology↗