Transcriptome analysis of Holotrichia oblita reveals differentially expressed unigenes related to reproduction and development under different photoperiods

Holotrichia oblita (Faldermann) (Coleoptera: Scarabaeidae) is an insect whose feeding and mating behaviors occur at night. A scotophase is necessary for H. oblita reproduction. We used RNA sequencing (RNA-seq) to compare the expression patterns of H. oblita at five photoperiods (0:24, 8:16, 12:12, 16:8, and 24:0 h) (L:D). Compared to the control (24:0) (L:D), 161-684 differentially expressed unigenes (DEUs) were found in female samples, while 698-2322 DEUs were found in male samples. For all DEUs, a total of 92-1143 DEUs were allocated to 116-662 categories of gene ontology (GO), and 81-1116 DEUs were assigned into 77-286 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The iPath diagram showed that the DEUs generated by comparing female and male samples with photoperiods of 0:24 and 24:0, respectively, involved multiple metabolic pathways, such as carbohydrate metabolism, lipid metabolism, nucleotide metabolism, purine metabolism and glutathione metabolism. Most of these DEUs were upregulated. Finally, 13 DEUs related to reproduction and development were selected to confirm the consistency of relative expression between RNA-Seq and quantitative real-time polymerase chain reaction (qRT-PCR). Most of these comparison results agreed well, except for some qRT-PCR results that were not detected in male samples due to their low expression. These results provide useful information for understanding the dark-induced reproduction of H. oblita.