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1. The use of non-model Drosophila species to study natural variation in TOR pathway signaling

   https://doi.org/10.1371/journal.pone.0270436  

   Steenwinkel, Tessa E.; Hamre, Kailee K.; Werner, Thomas (September 2022, PLOS ONE)

   Min, Kyung-Jin (Ed.)

   Nutrition and growth are strongly linked, but not much is known about how nutrition leads to growth. To understand the connection between nutrition through the diet, growth, and proliferation, we need to study the phenotypes resulting from the activation and inhibition of central metabolic pathways. One of the most highly conserved metabolic pathways across eukaryotes is the Target of Rapamycin (TOR) pathway, whose primary role is to detect the availability of nutrients and to either induce or halt cellular growth. Here we used the model organism Drosophila melanogaster ( D . mel .) and three non-model Drosophila species with different dietary needs, Drosophila guttifera ( D . gut .), Drosophila deflecta ( D . def .), and Drosophila tripunctata ( D . tri .), to study the effects of dietary amino acid availability on fecundity and longevity. In addition, we inhibited the Target of Rapamycin (TOR) pathway, using rapamycin, to test how the inhibition interplays with the nutritional stimuli in these four fruit fly species. We hypothesized that the inhibition of the TOR pathway would reverse the phenotypes observed under conditions of overfeeding. Our results show that female fecundity increased with higher yeast availability in all four species but decreased in response to TOR inhibition. The longevity data were more varied: most species experienced an increase in median lifespan in both genders with an increase in yeast availability, while the lifespan of D . mel . females decreased. When exposed to the TOR inhibitor rapamycin, the life spans of most species decreased, except for D . tri , while we observed a major reduction in fecundity across all species. The obtained data can benefit future studies on the evolution of metabolism by showing the potential of using non-model species to track changes in metabolism. Particularly, our data show the possibility to use relatively closely related Drosophila species to gain insight on the evolution of TOR signaling. 

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2. Reduced male fertility of an Antarctic mite following extreme heat stress could prompt localized population declines

   https://doi.org/10.1007/s12192-023-01359-4  

   Benoit, Joshua B.; Finch, Geoffrey; Ankrum, Andrea L.; Niemantsverdriet, Jennifer; Paul, Bidisha; Kelley, Melissa; Gantz, J.D.; Matter, Stephen F.; Lee, Richard E.; Denlinger, David L. (September 2023, Cell Stress and Chaperones)

   Climate change is leading to substantial global thermal changes, which are particularly pronounced in polar regions. Few studies have examined the impact of heat stress on reproduction in Antarctic terrestrial arthropods, specifically how brief, extreme events may alter survival. We observed that sublethal heat stress reduces male fecundity in an Antarctic mite, yielding females that produced fewer viable eggs. Females and males collected from microhabitats with high temperatures showed a similar reduction in fertility. This impact is temporary, as indicated by recovery of male fecundity following return to cooler, stable conditions. The diminished fecundity is likely due to a drastic reduction in the expression of male-associated factors that occur in tandem with a substantial increase in the expression of heat shock proteins. Cross mating between mites from different sites confirmed that heat-exposed populations have impaired male fertility. However, the impact on fertility declines with time when the mites are allowed to recover under less stressful conditions, suggesting that the negative effects are transient. Modeling indicated that heat stress is likely to reduce population growth and that short bouts of non-lethal heat stress could have substantial effects on local populations of Antarctic arthropods. 

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3. Nebulous without white : annotated long-read genome assembly and CRISPR/Cas9 genome engineering in Drosophila nebulosa

   https://doi.org/10.1093/g3journal/jkac231  

   Sottolano, Christopher J.; Revaitis, Nicole T.; Geneva, Anthony J.; Yakoby, Nir; Arbeitman, ed., M. (September 2022, G3 Genes|Genomes|Genetics)

   Abstract The diversity among Drosophila species presents an opportunity to study the molecular mechanisms underlying the evolution of biological phenomena. A challenge to investigating these species is that, unlike the plethora of molecular and genetics tools available for D. melanogaster research, many other species do not have sequenced genomes; a requirement for employing these tools. Selecting transgenic flies through white (w) complementation has been commonly practiced in numerous Drosophila species. While tolerated, the disruption of w is associated with impaired vision, among other effects in D. melanogaster. The D. nebulosa fly has a unique mating behavior which requires vision, and is thus unable to successfully mate in dark conditions. Here, we hypothesized that the disruption of w will impede mating success. As a first step, using PacBio long-read sequencing, we assembled a high-quality annotated genome of D. nebulosa. Using these data, we employed CRISPR/Cas9 to successfully disrupt the w gene. As expected, D. nebulosa males null for w did not court females, unlike several other mutant strains of Drosophila species whose w gene has been disrupted. In the absence of mating, no females became homozygous null for w. We conclude that gene disruption via CRISPR/Cas9 genome engineering is a successful tool in D. nebulosa, and that the w gene is necessary for mating. Thus, an alternative selectable marker unrelated to vision is desirable. 

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4. Evaluation of Additional Drosophila suzukii Male-Only Strains Generated Through Remobilization of an FL19 Transgene

   https://doi.org/10.3389/fbioe.2022.829620  

   Yamamoto, Akihiko; Yadav, Amarish K.; Scott, Maxwell J. (March 2022, Frontiers in Bioengineering and Biotechnology)

   Drosophila suzukii (D. suzukii) (Matsumura, 1931; Diptera: Drosophilidae), also known as spotted wing Drosophila , is a worldwide pest of fruits with soft skins such as blueberries and cherries. Originally from Asia, D. suzukii is now present in the Americas and Europe and has become a significant economic pest. Growers largely rely on insecticides for the control of D. suzukii . Genetic strategies offer a species-specific environmentally friendly way for suppression of D. suzukii populations. We previously developed a transgenic strain of D. suzukii that produced only males on a diet that did not contain tetracycline. The strain carried a single copy of the FL19 construct on chromosome 3. Repeated releases of an excess of FL19 males led to suppression of D. suzukii populations in laboratory cage trials. Females died as a consequence of overexpression of the tetracycline transactivator (tTA) and tTA-activated expression of the head involution defective proapoptotic gene. The aim of this study was to generate additional male-only strains that carried two copies of the FL19 transgene through crossing the original line with a piggyBac jumpstarter strain. Males that carried either two chromosome 3 or a singleX-linked transgene were identified through stronger expression of the red fluorescent protein marker gene. The brighter fluorescence of the X-linked lines was likely due to dosage compensation of the red fluorescent protein gene. In total, four X-linked lines and eleven lines with two copies on chromosome 3 were obtained, of which five were further examined. All but one of the strains produced only males on a diet without tetracycline. When crossed with wild type virgin females, all of the five two copy autosomal strains examined produced only males. However, the single copy X-linked lines did not show dominant female lethality. Five of the autosomal lines were further evaluated for productivity (egg to adult) and male competition. Based on these results, the most promising lines have been selected for future population suppression experiments with strains from different geographical locations. 

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5. Is variation in female aggressiveness across Drosophila species associated with reproductive potential?

   https://doi.org/10.1098/rspb.2024.2301  

   Bath, Eleanor; Gleason, Jennifer M (April 2025, Proceedings of the Royal Society B: Biological Sciences)

   Aggression is a key determinant of fitness in many species, mediating access to mates, food and breeding sites. Variation in intrasexual aggression across species is likely to be driven by variation in resource availability and distribution. While males primarily compete over access to mates, females are likely to compete over resources to maximize offspring quantity and/or quality, such as food or breeding sites. To date, however, most studies have focused on male aggression, and we know little about drivers of female aggression across species. To investigate potential reproductive drivers of female aggression, we tested the relationship between three reproductive traits and aggression in eightDrosophilaspecies. Using machine learning classifiers developed forDrosophila melanogaster, we quantified aggressive behaviours displayed in the presence of yeast for mated and unmated females. We found that female aggression was correlated with ovariole number across species, suggesting that females who lay more eggs are more aggressive. A need for resources for egg production or oviposition sites may therefore be drivers of female aggression, though other potential hypotheses are discussed. 

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