Project description:Gene expression of two populations was compared at a daylength intermediate to the two population critical photoperiods after 0 and 6 days. Genes with interaction terms are candidates for involvement in long-day response. The mosquito Wyeomyia smithii overwinters in a larval diapause that is initiated, maintained and terminated by day length (photoperiod). We use a forward genetic approach to investigate covert transcriptional events involved in the termination of diapause following exposure to long-days. We incorporate a novel approach that compares two populations (DB - southern, DR - northern) that differentially respond to a single day length. After six long days, 50% of individuals of population DB have terminated diapause and are irrevocably committed to development, though no phenotyping differences are observed. We can compare gene expression between these two populations after six long days and zero long days. The zero long day treatment will control for evolved differences between the populations and the 6 long day treatment allows for the identification of genes that are differentially expressed due to different responses to a single daylength. We identify 30 transcripts associated with differential response to day length. All of the corresponding genes with a previously annotated function are consistent with a role in the termination of diapause, with downstream developmental events, or with the transition from potentially oxygen-poor to oxygen-rich environments; none appears to be specifically part of the photoperiodic switch mechanism itself. However, among 10 unannotated genes, a gene homologous to Drosophila melanogaster CG13043 emerges from three separate forward genetic screens as a leading candidate for a gene contributing to the photoperiodic timing mechanism itself (photoperiodic switch). We name this gene photoperiodic response gene 1 (prg1). Prg1 is up-regulated under long-day response conditions, is located under a QTL for critical photoperiod and is associated with critical photoperiod after 25 generations of recombination from a cross between extreme phenotypes. Three independent forward genetic approaches identify prg1 as a gene either involved in the photoperiodic switch mechanism or very tightly linked to a gene that is. We conclude that continued forward genetic approaches will be central to understanding not only the molecular basis of photoperiodism and diapause, but also the evolutionary potential of temperate and polar animal populations when confronted with rapid climate change. 4 treatments, (Population DR, Day 0; Population DB, Day 0; Population DR, Day 6, Population DB, Day6), one dye swap (treatment Cy3 or Cy5, each replicated three times for a total of 24 arrays

Project description:Gene expression of two populations was compared at a daylength intermediate to the two population critical photoperiods after 0 and 6 days. Genes with interaction terms are candidates for involvement in long-day response. The mosquito Wyeomyia smithii overwinters in a larval diapause that is initiated, maintained and terminated by day length (photoperiod). We use a forward genetic approach to investigate covert transcriptional events involved in the termination of diapause following exposure to long-days. We incorporate a novel approach that compares two populations (DB - southern, DR - northern) that differentially respond to a single day length. After six long days, 50% of individuals of population DB have terminated diapause and are irrevocably committed to development, though no phenotyping differences are observed. We can compare gene expression between these two populations after six long days and zero long days. The zero long day treatment will control for evolved differences between the populations and the 6 long day treatment allows for the identification of genes that are differentially expressed due to different responses to a single daylength. We identify 30 transcripts associated with differential response to day length. All of the corresponding genes with a previously annotated function are consistent with a role in the termination of diapause, with downstream developmental events, or with the transition from potentially oxygen-poor to oxygen-rich environments; none appears to be specifically part of the photoperiodic switch mechanism itself. However, among 10 unannotated genes, a gene homologous to Drosophila melanogaster CG13043 emerges from three separate forward genetic screens as a leading candidate for a gene contributing to the photoperiodic timing mechanism itself (photoperiodic switch). We name this gene photoperiodic response gene 1 (prg1). Prg1 is up-regulated under long-day response conditions, is located under a QTL for critical photoperiod and is associated with critical photoperiod after 25 generations of recombination from a cross between extreme phenotypes. Three independent forward genetic approaches identify prg1 as a gene either involved in the photoperiodic switch mechanism or very tightly linked to a gene that is. We conclude that continued forward genetic approaches will be central to understanding not only the molecular basis of photoperiodism and diapause, but also the evolutionary potential of temperate and polar animal populations when confronted with rapid climate change.

Project description:This study measured the differential expression of genes from two populations of Wyeomyia smithii in the USA that differ in their propensity to bite over a geographic gradient. Population KC is a northern non-biting population from Maine; population WI is a southern low-frequency biting population from Florida. The mosquitoes were maintained at the University of Oregon under standard rearing conditions and run through two generations to minimize maternal and field effects. Selection for biting was conducted using ~14,000 individuals from the WI population. The environment and protocols used for selection were the same as for KC except biters were removed from their cage and placed into a separate “biting” cage with supplemental males from the same generation of the selected line. All hatch from the biting cage were used to generate the subsequent generations. This protocol was followed until the selected line had undergone 5 generation of selection. Through all generations of selection, including those that were not offered a host, hatch were placed on short days (LL:D=10:14) at 21°C to synchronize each generation and to miigate inadvertant direct selection on development time, generation time, or the timing of reproductive allocation. After adults of a given generation had died, their offspring were transferred to long days and reared to adulthood, as above. During experiments, all animals were in good physical condition. Animal heads were dissected then transferred into 1.5-ml microcentrifuge tubes and shock-frozen in liquid nitrogen. Samples were short-term stored at -80°C. For all experimental conditions, four independent replicates (50 heads each) were analyzed. This GEO record is for three comparisons among the three populations: (EXP1) non-biters in the base population (WI) versus biting individuals in the WI line selected for biting (WIOB) over 5 generations of selection (WI vs WIOB); (EXP2) WIOB versus northern obligate non-biters (KC); (3) WI versus KC (n=4 per treatment group for each population).

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Wyeomyia smithii

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