Chronic contact with realistic soil concentrations of imidacloprid affects the mass, immature development speed, and adult longevity of solitary bees.

The non-target effects of pesticides are an area of growing concern, particularly for ecologically and economically important organisms such as bees. Much of the previous research on the effects of neonicotinoids, a class of insecticide that has gained attention for non-target effects, on bees focused on the consumption of contaminated food resources by a limited number of eusocial species. However, neonicotinoids are known to accumulate and persist in soils at concentrations 2 to 60 times greater than in food resources, and may represent an important route of exposure for diverse and ecologically important ground-nesting bees. This study aimed to assess the effect of chronic contact exposure to realistic soil concentrations of imidacloprid, the most widely used neonicotinoid pesticide, on bee longevity, development speed, and body mass. Cohorts of Osmia lignaria and Megachile rotundata were used as proxies for ground-nesting species. We observed species- and sex-specific changes to adult longevity, development speed, and mass in response to increasing concentrations of imidacloprid. These results suggest that chronic exposure to nesting substrates contaminated with neonicotinoids may represent an important route of exposure that could have considerable physiological and ecological consequences for bees and plant-pollinator interactions.

Inversions and adaptation to the plant toxin ouabain shape DNA sequence variation within and between chromosomal inversions of Drosophila subobscura.

Adaptation is defined as an evolutionary process allowing organisms to succeed in certain habitats or conditions. Chromosomal inversions have the potential to be key in the adaptation processes, since they can contribute to the maintenance of favoured combinations of adaptive alleles through reduced recombination between individuals carrying different inversions. We have analysed six genes (Pif1A, Abi, Sqd, Yrt, Atpα and Fmr1), located inside and outside three inversions of the O chromosome in European populations of Drosophila subobscura. Genetic differentiation was significant between inversions despite extensive recombination inside inverted regions, irrespective of gene distance to the inversion breakpoints. Surprisingly, the highest level of genetic differentiation between arrangements was found for the Atpα gene, which is located outside the O1 and O7 inversions. Two derived unrelated arrangements (O3+4+1 and O3+4+7) are nearly fixed for several amino acid substitutions at the Atpα gene that have been described to confer resistance in other species to the cardenolide ouabain, a plant toxin capable of blocking ATPases. Similarities in the Atpα variants, conferring ouabain resistance in both arrangements, may be the result of convergent substitution and be favoured in response to selective pressures presumably related to the presence of plants containing ouabain in the geographic locations where both inversions are present.

Preparation of Drosophila tissue culture cells from different stages of the cell cycle for chromatin immunoprecipitation using centrifugal counterflow elutriation and fluorescence-activated cell sorting.

Many nuclear proteins alter their localization during the cell cycle. This includes proteins which regulate and execute cell cycle events and proteins involved in transcription and DNA repair. The core components of chromatin, the histone proteins, also change their modification state through the cell cycle. Chromatin immunoprecipitation (ChIP) makes it possible to localize chromatin-associated proteins to specific sequences in the genome and has revolutionized studies of transcription. Fewer studies have used ChIP to analyze protein localization or modification at specific stages in the cell cycle. This is in part because these studies require isolation of pure populations of cells at each stage of the cell cycle, which is challenging for many cell types. However, the ability to carry out ChIP from cells at specific stages in the cell cycle in some systems has revealed cell cycle regulation of chromatin localization, and cell cycle stage-specific functions and modification of chromatin proteins, providing incentive to pursue these experiments. This chapter presents protocols for isolating Drosophila S2 cells from all phases of the cell cycle using centrifugal elutriation and fluorescent-activated cell sorting. These cells are suitable for ChIP analysis.