Key molecular processes of the diapause to post‐diapause quiescence transition in the alfalfa leafcutting bee Megachile rotundata identified by comparative transcriptome analysis

Abstract

Insect diapause (dormancy) synchronizes an insect's life cycle to seasonal changes in the abiotic and biotic resources required for development and reproduction. Transcription analysis of diapause to post‐diapause quiescent transition in the alfalfa leafcutting bee Megachile rotundata Fabricius identifies 643 post‐diapause up‐regulated gene transcripts and 242 post‐diapause down‐regulated transcripts. The log2 fold change in gene expression levels ranges from −5 to 7. Transcripts from several pivotal diapause‐related processes, including chromatin remodelling, cellular signalling pathways, microRNA processing, anaerobic glycolysis, cell cycle arrest and neuroendocrine control, are identified as being differentially expressed during the diapause to post‐diapause transition. In conjunction with studies from other insect species, the data indicate that there are several common mechanisms of diapause control and maintenance.

Cell cycle regulator, small silencing RNA, and segmentation patterning gene expression in relation to embryonic diapause in the band-legged ground cricket

“…In this case, reduction of the piRNA pathway could be 367 important for the switch from direct development to diapause. In addition, AGO2 RNA 368 is drastically upregulated in postdiapause larvae in the leaf-cutting bee Megachile 369 rotundata (Yocum et al, 2015). We assumed some difference between long-day and The segment polarity genes are expressed in the embryo following expression of the 383 gap and pair-rule genes (Akam, 1987).…”

Conceptual framework of the eco-physiological phases of insect diapause development justified by transcriptomic profiling

“…Since the publication of the pioneering paper of Denlinger and coworkers (29), a number of studies have described differences in gene transcription linked to insect diapause (20,(30)(31)(32)(33)(34)(35)(36). Indeed, some authors have attempted to integrate these studies and to detect commonalities in the diapause transcriptional profiles of different species, searching for the hypothetical genetic toolkit of diapause (18,19). Two genes have been specifically suggested as potential general markers for distinguishing between diapause and direct development, phosphoenolpyruvate carboxykinase (pepck), which is up-regulated in diapause, and proliferating cell nuclear antigen (pcna), which is down-regulated in diapause (18).…”

“…Thus, hibernation is widespread in polar and temperate regions, aestivation often occurs in Mediterranean and other dry climate zones, and tropical diapauses may respond to seasonality primarily in biotic interactions (14)(15)(16). Despite this diversity in insect diapause responses, several phenotypic features occur almost ubiquitously: developmental arrest, metabolic suppression, and environmental stress resistance (17), so that some authors have proposed the notion of a common genetic "toolkit" for diapause (18,19). According to this scheme, some common diapause-induced gene-expression profiles might be shared across insect (or even across invertebrate) taxa.…”

Transcriptional profiling of overwintering gene expression in the small carpenter bee, Ceratina calcarata

“…We characterize gene expression profiles of field-collected overwintering C. calcarata and contrast these against previously published active season gene expression profiles in the same species (Rehan et al 2014). Based on existing overwintering gene expression literature (Colinet et al 2007(Colinet et al , 2012Dunning et al 2013Dunning et al , 2014Lee et al 1998;Purac et al 2008;Ragland et al 2010;Rinehart et al 2007Rinehart et al , 2010Robich et al 2007;Torson et al 2015;Qin et al 2005;Yocum et al 2005Yocum et al , 2015, we predict that differential expression would be found in genes relating to heat shock proteins, membrane lipids, cuticular proteins, and cytoskeletal and muscular alterations. We also provide comparisons of our results to previous studies on overwintering gene expression and cold tolerance in other insects, in order to assess whether similar or different genes and pathways are associated with overwintering across taxa.…”

“…Lists of differentially expressed transcripts, uniquely expressed transcripts (expressed in only one female group), and lists of enriched GO terms from overwintering C. calcarata were compared to transcriptomic studies of cold-related gene expression on fruit fly (D. melanogaster; Zhang et al 2011;Telonis-Scott et al 2009), flesh fly (Sarcophaga crassipalpis ; Rinehart et al 2010), Asian tiger mosquito (Aedes albopictus ; Poelchau et al 2013), and the leafcutter bee (Megachile rotundata ; Torson et al 2015;Yocum et al 2015). We identified putatively homologous s e q u e n c e s b e t w e e n C .…”