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Study by EvoPAD researchers sheds new light on evolution and maintenance of sex
The vast majority of eukaryotes reproduces sexually, yet, the evolution and maintenance of sexual reproduction remains a puzzle in evolutionary biology. Reproducing sexually comes with high costs: Each sexually reproducing organism can only produce half as many offspring as an asexually reproducing organism (since only the females bear offspring and they usually make up only 50% of the population). In addition, finding a mate requires energy and may increase predation risk. To balance these costs, sexual reproduction must have benefits. One such benefit may be genetic diversity generated by reshuffling of maternal and paternal alleles. However, many organisms perform self-fertilization, meaning they undergo sexual reproduction without a partner involved and thus without generating new genetic variation. Another, so far rather neglected hypothesis is that the molecular mechanisms underlying sexual reproduction overlap with those of the cellular stress-response thereby providing a direct fitness advantage to the individual when engaging in sexual reproduction under stressful conditions. Together with colleagues from the National Research Council in Naples, Italy, EvoPAD researchers Valerio Vitali and Francesco Catania tested this hypothesis in the ciliate Paramecium tetraurelia and published the results in the May issue of Genome Biology and Evolution, which also contains a Highlight profile of their manuscript. Their results show that self-fertilizing Paramecium cells are much more likely to survive after a heat-shock compared to genetically identical cells that divide asexually. Results from transcriptional data suggest that heat-shock proteins may play a role in meiosis/fertilization and the response to environmental stress at the same time. They also reveal connections between metabolism and developmental program, which are reminiscent of observations in multicellular organisms. These results indicate that sexually reproducing organisms may gain direct fitness benefits through an overlap in the molecular processes involved in sexual reproduction and stress response thereby contributing to the prevalence of sex.
EvoPAD PI Francesco Catania featured in Quanta magazine
EvoPAD PI Dr Francesco Catania is featured in a recent article discussing new insights into the evolution of sexual reproduction in Quanta magazine. Quanta magazine is an online publication aiming to enhance public understanding of science by reporting developments in mathematics, theoretical physics, theoretical computer science and the basic life sciences in an accessible manner to a broad audience. In the article, Francesco and others argue that while sexual reproduction usually carries costs to individuals and is thought to mainly benefit future generations through increasing genetic diversity, it may also directly benefit the individual engaging in sexual reproduction - especially in stressful environments. The basis for the article is a recent study headed by Francesco and EvoPAD PhD student Valerio Vitali published in Genome Biology and Evolution showing that self-fertilization can enhance stress resistance to starvation in the ciliate Paramecium tetraurelia.
New study on the variability and dynamics of Bacillus thuringiensis infections in Tenebrionid beetles
Bacteria of the species Bacillus thuringiensis are the most commonly used bioinsecticide. Those bacteria produce toxins that are activated upon ingestion in the insects’ gut and can lead, in some species, to midgut disruption leading to death by septicaemia. In a newly published study in Insects journal, EvoPAD researchers Ana Sofia Lindeza and Joachim Kurtz and colleague Caroline Zanchi adapted a non-invasive assay to study gut leakage, the Smurf assay, to two species of Tenebrionid beetles, the mealworm beetle Tenebrio molitor and the red flour beetle Tribolium castaneum. The Smurf assay uses a blue food dye that does not cross the healthy intestinal barrier but leaks into the hemocoel upon disruption of the intestinal barrier, giving the animals the characteristic blue stain after which it is named. The researchers used the assay to investigate the variability of hosts in the susceptibility to gut leakage and compared mortality and gut leakage induced by two different B. thuringiensis strains using as host systems. Results from their experiments show that younger and smaller larvae of T. molitor suffer higher mortality and die faster upon exposure to B. thuringiensis var. tenebrionis. However, this higher mortality was not accompanied by a higher incidence of gut leakage in small larvae as shown in the Smurf assay. In T. castaneum, they used the Smurf assay to compare exposure of larvae to the two B. thuringiensis strains var. tenebrionis and var. tolworthi. Larvae exposed to B. thuringiensis tenebrionis died faster and had a higher mortality 7 days after exposure. However, according to the Smurf assay there was no difference in the leakiness of the gut after exposure to the different strains. Interestingly, in both host systems, the occurrence of a Smurf phenotype indicating gut disruption was very low (less than 10%). These results could indicate that contrary to prior expectations, extensive gut leakage is not a widespread killing mechanism of B. thuringiensis in T. molitor and T. castaneum. Alternative mechanism to gut’s leakage may include toxemia or starvation due to arrested feeding.
Visit by Mercator Fellow Thomas Flatt cancelled due to SARS-CoV-2 pandemic
This year's visit by EvoPAD Mercator Fellow Thomas Flatt had to be cancelled due to the measures to stem the spread of SARS-CoV-2. It is planned that he will visit EvoPAD again in 2021.
New study on the effects of different feeding routines on welfare in laboratory mice
Animals in their natural habitats have to spend a large proportion of their time and energy to forage for food of varying nutritional values in many different places. Complex mechanisms have evolved to optimize this foraging behavior and maximize the achieved energy intake. If, however, food is readily available in abundance, these mechanisms are no longer adaptive and can cause severe health impairments. In a laboratory setting, for example, mice are given unrestricted access to high-energy food around the clock, which, correspondingly, has been linked to obesity and comorbidities. In contrast, reducing the animals’ body weight by feeding them less food once per day has been shown to enhance life span and reduce the vulnerability to disease.
Against this background, a new study by EvoPAD researchers Janina Feige-Diller, Sylvia Kaiser, Norbert Sachser, S. Helene Richter and colleagues published in Frontiers in Veterinary Science compared the effects of different feeding routines on the quality of life of laboratory mice. The results show that removing the food for 4 h per day did not lead to a reduction of body weight, and hence is unlikely to prevent negative effects of overfeeding. In contrast, feeding less food once per day or automatically supplying less food as small pieces all over the day led to the aspired body weight reduction. For the latter feeding routine, however, behavioral and physiological changes were found which implied a rather negative impact on welfare. By contrast, no distinct negative effects were found for feeding a reduced amount of food once per day.