Project description:Sexual reproduction brings genes from two parents â matrigenes and patrigenes â into one individual. These genes, despite being unrelated, should show nearly perfect cooperation because each gains equally through production of offspring. However, an individualâs matrigenes and patrigenes can have different probabilities of being present in other relatives, so that kin selection could act on them differently. Such intragenomic conflict could be implemented by partial or complete silencing (imprinting) of an allele by one of the parents. Evidence supporting this theory is seen in offspring-mother interactions, with patrigenes favoring acquisition of more of the mother's resources if some of the costs fall on half siblings who do not share the patrigene. The kinship theory of intragenomic conflict is little tested in other contexts, but it predicts that matrigene-patrigene conflict may be rife in social insects. We tested the hypothesis that honey bee worker reproduction is promoted more by patrigenes than matrigenes by comparing across 9 reciprocal crosses of two distinct genetic stocks. As predicted, hybrid workers show reproductive trait characteristics of their paternal stock, indicating enhanced activity of the patrigenes on these traits, greater patrigenic than matrigenic expression, and significantly increased patrigenic biased expression in reproductive workers. These results support both the general prediction that matrigene-patrigene conflict occurs in social insects and the specific prediction that honey bee worker reproduction is driven more by patrigenes. The success of these predictions suggests that intragenomic conflict may occur in many contexts where matrigenes and patrigenes have different relatednesses to affected kin. Testing the kinship theory of intragenomic conflict in honey bees
Project description:Sexual reproduction brings genes from two parents – matrigenes and patrigenes – into one individual. These genes, despite being unrelated, should show nearly perfect cooperation because each gains equally through production of offspring. However, an individual’s matrigenes and patrigenes can have different probabilities of being present in other relatives, so that kin selection could act on them differently. Such intragenomic conflict could be implemented by partial or complete silencing (imprinting) of an allele by one of the parents. Evidence supporting this theory is seen in offspring-mother interactions, with patrigenes favoring acquisition of more of the mother's resources if some of the costs fall on half siblings who do not share the patrigene. The kinship theory of intragenomic conflict is little tested in other contexts, but it predicts that matrigene-patrigene conflict may be rife in social insects. We tested the hypothesis that honey bee worker reproduction is promoted more by patrigenes than matrigenes by comparing across 9 reciprocal crosses of two distinct genetic stocks. As predicted, hybrid workers show reproductive trait characteristics of their paternal stock, indicating enhanced activity of the patrigenes on these traits, greater patrigenic than matrigenic expression, and significantly increased patrigenic biased expression in reproductive workers. These results support both the general prediction that matrigene-patrigene conflict occurs in social insects and the specific prediction that honey bee worker reproduction is driven more by patrigenes. The success of these predictions suggests that intragenomic conflict may occur in many contexts where matrigenes and patrigenes have different relatednesses to affected kin.
Project description:Kin selection may act differently on genes inherited from the two parents (matrigenes and patrigenes), resulting in intragenomic conflict. This conflict can be observed as differential expression of matrigenes and patrigenes, or parent specific gene expression (PSGE). In honey bees (Apis mellifera), intragenomic conflict is hypothesized to occur in multiple social contexts. Previously, we found patrigene expression in reproductive tissues was associated with increased reproductive potential in worker honey bees, consistent with the prediction that patrigenes are selected to promote selfish behavior in this context. Here, we examined brain expression patterns to determine if PSGE is also found in other tissues. As before, the number of transcripts showing patrigene expression bias was significantly greater in the brains of reproductive versus sterile workers, while the number of matrigene-biased transcripts was not significantly different. Twelve transcripts out of the 374 showing PSGE in either tissue showed PSGE in both brain and reproductive tissues; this overlap was significantly greater than expected by chance. However, the majority of transcripts showed PSGE only in one tissue, suggesting the epigenetic mechanisms mediating PSGE show plasticity between tissues. There was no significant overlap between transcripts that showed PSGE and transcripts that were significantly differentially expressed. Weighted gene correlation network analysis identified modules which were significantly enriched in both types of transcripts, suggesting that these genes may influence each other through gene networks. Our results provide further support for the kin selection theory of intragenomic conflict, and provide valuable insights into the mechanisms which may mediate this process.
Project description:Integrons are genetic elements that enable bacterial adaptation by collecting new genes encoded in integron cassettes (ICs) to create a reservoir of adaptive functions. These cassettes typically lack their own promoters and rely on the integron platform for their expression. Integrons, well-known for spreading antibiotic resistance genes in clinically relevant Gram-negative species, include Mobile Integrons (MIs), that transport over 170 resistance genes. In contrast, Sedentary Chromosomal Integrons (SCIs), ubiquitous in Vibrio species, are primarily found within bacterial chromosomes. However, their functions are not related to antimicrobial resistance and are largely unexplored. SCIs, typified by the Superintegron (SI) in Vibrio cholerae, represent ancient and highly variable regions in bacterial genomes. The SI is extensive, housing 179 integron cassettes, mostly with unknown functions. Although 19 cassettes encode toxin-antitoxin (TA) systems, which stabilize the array, the intricacies of the SI are challenging to study due to its size and unique integrase. To investigate the SI's impact on V. cholerae, we developed the SeqDelTA approach, enabling the gradual deletion of the SI. This deletion facilitates the use of standard genetic tools without SI interference. Our in-depth analysis of the resulting ∆SI strain, covering various aspects, demonstrated no significant alterations in V. cholerae's physiology. Despite their extended coevolution, SCIs appear to be genetically isolated from the host genome.
Project description:Several groups have shown that through evolution experiments, tolerance and resistance evolved rapidly under cyclic antibiotic treatment. In other words, intermittent antibiotic exposure performed in a typical adaptive laboratory evolution (ALE) experiments will “train” the bacteria to become tolerant/resistant to the drug. Although ALE has added new knowledge regarding the impact of varying treatment conditions on the evolution of tolerance/resistance, the role of some parameters such as population bottlenecks remains poorly understood. In this study, we employed ALE to investigate the evolution of methicillin-resistant S. aureus under repetitive daptomycin treatment using a modified protocol that incorporated population bottleneck following antibiotic exposure. We observed that although tolerance development is slower under bottlenecking conditions, the populations finally attained tolerance mutation in the yycH gene after twelve cycles of treatment. Extending the evolution experiment and changing the treatment scheme to a fast evolution protocol (treatment during exponential phase without bottlenecking) led to the emergence of daptomycin resistance (mutation in mprF gene). Through proteomics, we uncovered the differential adaptation strategies of these daptomycin tolerant and resistant MRSA strains, and how they respond differently to antibiotics compared to the ancestral wild-type.
Project description:Virulence is a key trait under selection during host-parasite coevolution. In order to obtain increased fitness, parasites are predicted to increase their ability to circumvent and overcome host immunity. A particular challenge for pathogens are external immune systems, found among various invertebrates. Such external immune systems are chemical defence systems comprised of highly potent antimicrobial compounds released by prospective hosts into the environment. We carried out a coevolution experiment with the entomopathogenic fungus, Beauveria bassiana, and the red flour beetle, Tribolium castaneum, which has a well-documented external immune system. Surprisingly, after just seven transfers of experimental evolution we saw a significant increase in virulence in all B. bassiana. This increase in virulence was mainly the result of the B. bassiana isolates evolving resistance to the external immune defences of the T. castaneum beetles, but not obviously through the increased production of toxins or other harmful substances. Furthermore, transcriptomic analyses of B. bassiana RNA-seq data implicates up-regulation of genes responsible for resistance to oxidative stress underlying the observed resistance. We conclude that external immunity acts as a powerful selective force for virulence evolution, with an increase in virulence being achieved apparently entirely by overcoming these defences, most likely due to elevated oxidative stress resistance.