Biology subjects

Montooth, K. L.

Publications and source records attributed to Montooth, K. L..

3 recordsLinked to original sources

bioRxiv2018

Energetic stress and infection generate immunity-fecundity tradeoffs in Drosophila

Physiological responses to short-term environmental stress, such as infection, can have long-term consequences for fitness, particularly if the responses are inappropriate or nutrient resources are limited. Genetic variation affecting energy acquisition, storage, and usage can limit cellular energy availability and may influence resource-allocation tradeoffs even when environmental nutrients are plentiful. Here, we utilize well-characterized Drosophila mitochondrial-nuclear genotypes to test whether disrupted energy metabolism interferes with nutrient-sensing pathways, and whether this disruption has consequences for tradeoffs between immunity and fecundity. We find that this energetically compromised genotype is resistant to rapamycin - a drug that stimulates nutrient-sensing pathways that are activated when resources are limited. Resource limitation also compromises survival in energetically-compromised genotypes, suggesting that this genotype may have little excess energetic capacity and fewer cellular nutrients, even when environmental nutrients are not limiting. Accordingly, we find that immune function is compromised in this genotype, but only in females, and that these females experience immunity-fecundity tradeoffs that are not evident in genotypic controls with normal energy metabolism. Thus, genetic variation in energy metabolism may act to limit the resources available for allocation to life-history traits in ways that generate tradeoffs even when environmental resources are not limiting.

genetics↗

bioRxiv2017

Energy demand and the context-dependent effects of genetic interactions

Genetic effects are often context dependent, with the same genotype differentially affecting phenotypes across environments, life stages, and sexes. We used an environmental manipulation designed to increase energy demand during development to investigate energy demand as a general physiological explanation for context-dependent effects of mutations, particularly for those mutations that affect metabolism. We found that increasing the photoperiod during which Drosophila larvae are active during development phenocopies a temperature-dependent developmental delay in a mitochondrial-nuclear genotype with disrupted metabolism. This result indicates that the context-dependent fitness effects of this genotype are not specific to the effects of temperature and may generally result from variation in energy demand. The effects of this genotype also differ across life stages and between the sexes. The mitochondrial-nuclear genetic interaction disrupts metabolic rate in growing larvae, but not in adults, and compromises female, but not male, reproductive fitness. These patterns are consistent with a model where context-dependent genotype-phenotype relationships may generally arise from differences in energy demand experienced by individuals across environments, life stages, and sexes.\n\nIMPACT SUMMARYGenetic effects on traits are often context dependent, such that a genotype that improves fitness under one context may have no effect or even a deleterious effect in another context. The external environment is a common context that affects the degree to which a genotype determines a phenotype, but the internal environment of an organism (e.g., its genetic background, sex or life stage) also provides an important context that may modify the phenotypic expression of a genotype. Here we combine new data on the phenotypic effects of a well-characterized genetic interaction between the mitochondrial and nuclear genomes of the fruit fly Drosophila with prior observations to support a model of energy demand as a general explanation for context-dependent genetic effects, particularly for mutations that affect metabolism. We show that the magnitude of fitness effects of this genetic interaction correlates positively with the degree of energy demand among developmental treatments that accelerate growth rate, across developmental stages that differ in the cost of growth, and between sexes with potentially different costs of reproduction. These internal and external contexts create variable demands on energy metabolism that will impact the efficacy of natural selection acting on metabolic mutations in populations.

evolutionary biology↗

bioRxiv2017

Maternal loading of a small heat shock protein increases embryo thermal tolerance in Drosophila melanogaster

Maternal investment is likely to have direct effects on offspring survival. In oviparous animals whose embryos are exposed to the external environment, maternal provisioning of molecular factors like mRNAs and proteins may help embryos cope with sudden changes in the environment. Here we sought to modify the maternal mRNA contribution to offspring embryos and test for maternal effects on acute thermal tolerance in early embryos of Drosophila melanogaster. We drove in vivo overexpression of a small heat shock protein gene (Hsp23) in female ovaries and measured the effects of acute thermal stress on offspring embryonic survival and larval development. We report that overexpression of the Hsp23 gene in female ovaries produced offspring embryos with increased thermal tolerance. We also found that brief heat stress in the early embryonic stage (0 to 1 hour-old) caused decreased larval performance later in life (5 to 10 days-old), as indexed by pupation height, as well as increased development time to pupation. Maternal overexpression of Hsp23 protected embryos against these heat-induced larval defects. Our data demonstrate that transient products of single genes have large and lasting effects on whole-organism environmental tolerance. Further, our results suggest that maternal effects have a profound impact on offspring survival in the context of thermal variability.\n\nSUMMARY STATEMENTA gene-specific maternal effect confers thermal tolerance to offspring embryos in the fruit fly Drosophila melanogaster.

evolutionary biology↗