Transcriptome analysis of the brain under diapause and nondiapause conditions in the blowfly Protophormia terraenovae

Abstract

The blow fly Protophormia terraenovae responds to photoperiod and temperature to control reproductive diapause. Differentially expressed genes (DEGs) in the brain are investigated under diapause-inducing and diapause-averting conditions in search of potential genes for diapause induction. Total RNA is extracted from female brains 1–2.5 days after adult emergence under an LD 18 : 6 h photocycle at 25 °C as nondiapause samples and 3, 3.5, 7 and 7.5 days after adult emergence under an LD 12 : 12 h photocycle at 20 °C as diapause samples. From our transcriptome analysis, 626 350 654 reads are assembled into 126 231 contigs, from which 46 844 contigs (37.1% of the total) are annotated as protein-coding genes. Among them, the expression levels in 549 contigs are specifically up-regulated under diapause-inducing (44.1%) or diapause-averting (55.9%) conditions. Using quantitative real-time reverse transcriptase-polymerase chain reaction analysis, higher expression levels under diapause-inducing conditions are found in a contig encoding angiotensin-converting enzyme (ACE). Expression levels of the contig significantly increase 3 days after changing the photoperiod to diapause-inducing short days. Rabbit antisera against 17 amino acid peptides included in P. terraenovae-ACE stain one pair of cells lateral to the oesophageal foramen. These results suggest that the expression of a small number of genes is associated with the regulation of diapause in response to photoperiod and temperature, and ACE in the immunoreactive cells might respond to short days, which is why it is involved in diapause induction.