Environmental stress and reproduction in Drosophila melanogaster : starvation resistance, ovariole numbers and early age egg production

Background  

The Y model of resource allocation predicts a tradeoff between reproduction and survival. Environmental stress could affect a tradeoff between reproduction and survival, but the physiological mechanisms underlying environmental mediation of the tradeoff are largely unknown. One example is the tradeoff between starvation resistance and early fecundity. One goal of the present study was to determine if reduced early age fecundity was indeed a robust indirect response to selection for starvation resistance, by investigation of a set of D. melanogaster starvation selected lines which had not previously been characterized for age specific egg production. Another goal of the present study was to investigate a possible relationship between ovariole number and starvation resistance. Ovariole number is correlated with maximum daily fecundity in outbred D. melanogaster. Thus, one might expect that a negative genetic correlation between starvation resistance and early fecundity would be accompanied by a decrease in ovariole number.     

Evolution of starvation resistance in Drosophila melanogaster: measurement of direct and correlated responses to artificial selection

Laboratory selection for resistance to starvation has been conducted under relatively controlled conditions to investigate direct and correlated responses to artificial selection. With regard to starvation resistance, there are three physiological routes by which the trait can evolve: resource accumulation, energy conservation and starvation tolerance. A majority of energetic compounds and macromolecules including triglycerides, trehalose and other sugars, and soluble protein increased in abundance as a result of selection. Movement was additionally investigated with selected males moving less than control males and selected females exhibiting a similar response to selection. Results obtained from this study supported two of the possible evolutionary mechanisms for adaptation to starvation: energy compound storage and conservation. If the response to selection is based on an evolutionarily conserved pattern of genetic correlations (elevated lipid, elevated sugars and reduced movement), then the response to selection is medically relevant and the genetic architecture should be investigated in depth.     

An evolutionary expressed sequence tag analysis of Drosophila spermatheca genes

This study investigates genes enriched for expression in the spermatheca, the long-term sperm storage organ (SSO) of female Drosophila. SSO genes are likely to play an important role in processes of sexual selection such as sperm competition and cryptic female choice. Although there is keen interest in the mechanisms of sexual selection at the molecular level, very little is known about the female genes that are involved. In the present study, a high proportion of genes enriched for expression in the spermatheca are evolving rapidly. Most of the rapidly evolving genes are proteases and genes of unknown function that could play a specialized role in the spermatheca. A high percentage of the rapidly evolving genes have secretion signals and thus could encode proteins that directly interact with ejaculate proteins and coevolve with them. In addition to identifying rapidly evolving genes, the present study documents categories of genes that could play a role in spermatheca function such as storing, maintaining, and utilizing sperm. In general, candidate genes discovered in this study could play a key role in sperm competition, cryptic female choice of sperm, and sexually antagonistic coevolution, and ultimately speciation.     

Selection against genetic defects in conservation schemes while controlling inbreeding

We studied different genetic models and evaluation systems to select against a genetic disease with additive, recessive or polygenic inheritance in genetic conservation schemes. When using optimum contribution selection with a restriction on the rate of inbreeding (ΔF) to select against a disease allele, selection directly on DNA-genotypes is, as expected, the most efficient strategy. Selection for BLUP or segregation analysis breeding value estimates both need 1–2 generations more to halve the frequency of the disease allele, while these methods do not require knowledge of the disease mutation at the DNA level. BLUP and segregation analysis methods were equally efficient when selecting against a disease with single gene or complex polygene inheritance, i.e. knowledge about the mode of inheritance of the disease was not needed for efficient selection against the disease. Smaller schemes or schemes with a more stringent restriction on ΔF needed more generations to halve the frequency of the disease alleles or the fraction of diseased animals. Optimum contribution selection maintained ΔF at its predefined level, even when selection of females was at random. It is argued that in the investigated small conservation schemes with selection against a genetic defect, control of ΔF is very important.     

Profiling of T‐cell receptor signaling complex assembly in human CD4 T‐lymphocytes using RP protein arrays

The RP protein (RPP) array approach immobilizes minute amounts of cell lysates or tissue protein extracts as distinct microspots on NC‐coated slide. Subsequent detection with specific antibodies allows multiplexed quantification of proteins and their modifications at a scale that is beyond what traditional techniques can achieve. Cellular functions are the result of the coordinated action of signaling proteins assembled in macromolecular complexes. These signaling complexes are highly dynamic structures that change their composition with time and space to adapt to cell environment. Their comprehensive analysis requires until now relatively large amounts of cells (>5×10⁷) due to their low abundance and breakdown during isolation procedure. In this study, we combined small scale affinity capture of the T‐cell receptor (TCR) and RPP arrays to follow TCR signaling complex assembly in human ex vivo isolated CD4 T‐cells. Using this strategy, we report specific recruitment of signaling components to the TCR complex upon T‐cell activation in as few as 0.5 million of cells. Second‐ to fourth‐order TCR interacting proteins were accurately quantified, making this strategy specially well‐suited to the analysis of membrane‐associated signaling complexes in limited amounts of cells or tissues, e.g., ex vivo isolated cells or clinical specimens.     

In vitro metabolism of juvenile hormone III and juvenile hormone III bisepoxide by Drosophila melanogaster and mammalian cytosolic epoxide hydrolase

In vitro metabolism of juvenile hormone III (JH III) and juvenile hormone III bisepoxide was investigated using purified mouse liver cytosolic epoxide hydrolase (cEH) and cell fractions from Drosophila melanogaster. JH III was metabolized faster than JH III bisepoxide by epoxide hydrolase activity in D. melanogaster cell fractions and by cEH. After incubation with JH III bisepoxide, all cell fractions and cEH produced epoxy-diol, cis- and trans-tetrahydrofuran-diols, and tetraol as metabolites. An increase in the concentration of cEH resulted in an increase in the proportion of tetraol as a JH III bisepoxide metabolite but this trend was not observed in the D. melanogaster cell fractions. Differences between cell fractions in the metabolism of JH III and JH III bisepoxide suggests the presence of juvenile hormone epoxide hydrolase isozymes.