Diapause, a programmed developmental arrest primarily induced by seasonal environmental changes, is very common in the animal kingdom, and found in vertebrates and invertebrates alike. Diapause provides an adaptive advantage to animals, as it increases the odds of surviving adverse conditions. In insects, individuals perceive photoperiodic cues and modify endocrine signaling to direct reproductive diapause traits, such as ovary arrest and increased fat accumulation. However, it remains unclear as to which endocrine factors are involved in this process and how they regulate the onset of reproductive diapause. Here, we found that the long day-mediated drop in the concentration of the steroid hormone ecdysone is essential for the preparation of photoperiodic reproductive diapause in Colaphellus bowringi, an economically important cabbage beetle. The diapause-inducing long-day condition reduced the expression of ecdysone biosynthetic genes, explaining the drop in the titer of 20-hydroxyecdysone (20E, the active form of ecdysone) in female adults. Application of exogenous 20E induced vitellogenesis and ovarian development but reduced fat accumulation in the diapause-destined females. Knocking down the ecdysone receptor (EcR) in females destined for reproduction blocked reproductive development and induced diapause traits. RNA-seq and hormone measurements indicated that 20E stimulates the production of juvenile hormone (JH), a key endocrine factor in reproductive diapause. To verify this, we depleted three ecdysone biosynthetic enzymes via RNAi, which confirmed that 20E is critical for JH biosynthesis and reproductive diapause. Importantly, impairing Met function, a component of the JH intracellular receptor, partially blocked the 20E-regulated reproductive diapause preparation, indicating that 20E regulates reproductive diapause in both JH-dependent and -independent manners. Finally, we found that 20E deficiency decreased ecdysis-triggering hormone signaling and reduced JH production, thereby inducing diapause. Together, these results suggest that 20E signaling is a pivotal regulator that coordinates reproductive plasticity in response to environmental inputs.

Chrysomya megacephala (Fabricius) is a prevalent and synanthropic blowfly which has two sides, for being a pathogenic vector, an efficient pollinator, a promising resource of proteins, lipids, chitosan, biofuel et al., and an important forensic indicator. Moreover olfactory proteins are crucial component to function in related processes. However, the genomic platform of C. megacephala remains relatively unavailable. Developmental transcriptomes of eggs, larvae from 1st instar to before pupa stage and adults from emergence to egg laying period were built by RNA-sequencing to establish sequence background of C. megacephala with special lights on olfactory proteins. Clean reads in eggs, larvae and adults were annotated into 59486 transcripts. Transcripts were assembled into 22286, 17180, 18934 and 35900 unigenes in eggs, larvae, adults and the combined datasets, respectively. Unigenes were annotated using Nr (NCBI non-redundant protein sequences), Nt (NCBI non-redundant nucleotide sequences), GO (Gene Ontology), PFAM (Protein family), KOG/COG (Clusters of Orthologous Groups of proteins), Swiss-Prot (A manually annotated and reviewed protein sequence database), and KO (KEGG Orthology). Totally 12196 unigenes were annotated into 51 sub-categories belonging to three main GO categories; 8462 unigenes were classified functionally into 26 categories to KOG classifications; 5160 unigenes were functionally classified into 5 KEGG categories. Moreover, according to RSEM, the number of differentially expressed genes between larvae and eggs, adults and eggs, adults and larvae, and the common differentially expressed genes were 2637, 1804, 2628 and 258, respectively. Among them, 17 odorant-binding proteins (OBPs), 7 chemosensory proteins (CSPs) and 8 ionotropic receptors (IRs) were differently expressed in adults and larvae. Ten were confirmed as significant differentially expressed genes. Furthermore, OBP Cmeg32081-c4 was highly expressed in the female head and Cmeg33593_c0 were up-regulated with the increase of larval age. A comprehensive sequence resource with desirable quality was built by comparative transcriptome of eggs, larvae and adults, enriching the genomic platform of C. megacephala. The identified differentially expressed genes would facilitate the understanding of metamorphosis, development and the fitness to environmental change of C. megacephala. OBP Cmeg32081-c4 and Cmeg33593_c0 might play a crucial role in the interactions between olfactory system and biological processes.

House fly larvae provide a prolific and sustainable source of proteins used in poultry and fish feed. Wheat bran is a superior diet for house fly larvae and has been widely investigated to exploit its potential in the food and feed area. Using Illumina MiSeq 16S rDNA sequencing, this study investigated the gut microbiota of house fly larvae feeding on wheat bran and the bacterial community in the wheat bran. The bacterial communities in the house fly larvae were dominated by the phyla Proteobacteria and Firmicutes. Enterobacteriaceae and Providencia were the predominant bacteria at the family and genus levels, respectively. Some bacteria in the phyla Actinobacteria, Proteobacteria, Bacteroidetes and Firmicutes may be transferred from the gut of house flies to the wheat bran during feeding and may be involved in degrading and utilizing polysaccharides in the cell wall of wheat bran. The significance of the gut microbiota of house fly larvae, their transferring and roles in degradation of wheat bran is discussed. These findings regarding the gut microbiota of house fly larvae will provide opportunities for research on the impact of microbial communities on poultry and fish.