Deep sequencing reveals complex mechanisms of diapause preparation in the invasive mosquito, Aedes albopictus

Abstract

Seasonal environments present fundamental physiological challenges to a wide range of insects. Many temperate insects surmount the exigencies of winter by undergoing photoperiodic diapause, in which photoperiod provides a token cue that initiates an alternative developmental programme leading to dormancy. Pre-diapause is a crucial preparatory phase of this process, preceding developmental arrest. However, the regulatory and physiological mechanisms of diapause preparation are largely unknown. Using high-throughput gene expression profiling in the Asian tiger mosquito, Aedes albopictus, we reveal major shifts in endocrine signalling, cell proliferation, metabolism, energy production and cellular structure across pre-diapause development. While some hallmarks of diapause, such as insulin signalling and stress response, were not important at the transcriptional level, two genes, Pepck and PCNA, appear to show diapause-induced transcriptional changes across insect taxa. These processes demonstrate physiological commonalities between Ae. albopictus pre-diapause and diapause strategies across insects, and support the idea of a genetic 'toolkit' for diapause. Observations of gene expression trends from a comparative developmental perspective suggest that individual physiological processes are delayed against a background of a fixed morphological ontogeny. Our results demonstrate how deep sequencing can provide new insights into elusive molecular bases of complex ecological adaptations.

Photoperiodic Diapause and the Establishment ofAedes albopictus(Diptera: Culicidae) in North America

“…Several genes identified as differentially expressed as part of the diapause program in Ae. albopictus, such as pepck and fatty acid synthase, have also been implicated in the diapause response of other insects, implying a set of conserved genes that have been repeatedly acted on by natural selection during the independent evolution of diapause in diverse insect lineages (Poelchau et al 2013a, Denlinger and Armbruster 2014, Huang et al 2015. Finally, these results indicate that the altered regulation of fundamental physiological pathways that occurs during diapause can be used to identify genes underlying important ecological and stress resistance traits that may provide useful targets for vector control, even in species that don't undergo diapause.…”

“…Experimental design of RNAseq studies to identify the transcriptional basis of diapause in Ae. albopictus during the stages of diapause induction, preparation, and developmental arrest (Huang et al 2015;Poelchau et al 2011Poelchau et al , 2013aPoelchau et al , 2013b. The transcriptomes of mosquitoes reared under diapause-inducing and nondiapause inducing photoperiods are compared at different developmental stages (adult females, stage V oocytes, embryos 72-78 h post oviposition, embryos 135-141 h post oviposition, and eggs 11, 21, and 40 d post oviposition).…”

“…These results nicely illustrate that the diapause program can involve highly coordinated transcriptional regulation across a complex metabolic pathway. Another metabolism-related change is the increased expression of pepck, a gene which encodes a protein controlling the rate-limiting step of gluconeogenesis that has been implicated in the diapause response of other insects (Poelchau et al 2013a). Finally, the increased desiccation resistance of diapause eggs relative to nondiapause eggs is associated with increased abundance of a fatty acyl coA elongase (face) transcript under diapause conditions, both in mature oocytes before oviposition (Urbanski et al 2010) and during embryological development (Reynolds et al 2012).…”

Divergence of the diapause transcriptome in apple maggot flies: winter regulation and post-winter transcriptional repression

“…Photoperiodic responses can be readily manipulated in the lab, and numerous physiological and genetic studies have identified candidate genes and mechanisms that may transduce photoperiodic signals upstream and downstream of major hormonal cues (Emerson et al, 2010;Poelchau et al, 2013;Poupardin et al, 2015;Schmidt et al, 2008;Sim and Denlinger, 2008;Tauber et al, 2007;Wadsworth and Dopman, 2015;Williams et al, 2006). In contrast, it has been more difficult to experimentally manipulate temperature effects because the sensitivity of development to thermal conditions often changes over the course of diapause (Hodek and Hodkova, 1988).…”

An Experimental and Bioinformatics Protocol for RNA-seq Analyses of Photoperiodic Diapause in the Asian Tiger Mosquito, <em>Aedes albopictus</em>

“…Recent RNA-Seq studies on the transcriptional bases of diapause in the invasive and medically important mosquito Aedes albopictus provide a useful example of some of the experimental protocols that can be employed to successfully apply NGS technology to studying the molecular basis of a complex ecological adaptation in a non-model organism [8][9][10] . A. albopictus is a highly invasive species that is native to Asia but has recently invaded North America, South America, Europe, and Africa 11,12 .…”