Termination of diapause in response to long days in Wyeomyia smithii

ABSTRACT: 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.

ORGANISM(S): Wyeomyia smithii

PROVIDER: GSE18848 | GEO | 2010/02/13

SECONDARY ACCESSION(S): PRJNA121143

REPOSITORIES: GEO