Transcriptome based identification and tissue expression profiles of chemosensory genes in Blattella germanica (Blattaria: Blattidae)

Blattalla germanica is one of the most notorious household insect pests, and evolutionally more primitive than those well studied moths and flies, regarding the molecular mechanisms of chemosensation. In this study, we sequenced, for the first time, the antennal transcriptome of B. germanica using the Illumina HiSeq™ 2000 platform and then conducted the bioinformatic analysis of the data. In total, we identified 73 putative chemosensory genes, with 62 genes being novel in this species. These chemosensory genes included 48 odorant binding proteins (OBPs), 9 chemosensory proteins (CSPs), 6 sensory neuron membrane proteins (SNMPs), 5 odorant receptors (ORs) and 5 ionotropic receptors (IRs). Notably, Plus-C OBPs account for an exceptionally high proportion (39.58%) of the total 48 OBPs in this primitive insect. To predict the chemosensory functions of the genes, a detailed global tissue expression profiling was investigated by reverse transcription polymerase chain reaction (RT-PCR). Most OBP genes showed a chemosensory tissue biased profile, while CSP transcripts were widely and evenly expressed in different tissues. Furthermore, we found that more than half the chemosensory genes were expressed in the cerci, implying the important chemosensory functions of the organ in B. germanica. Taken together, our study provides important bases for elucidation of the molecular mechanisms and evolution of insect chemosensation, and for development of the chemosensation based techniques to control B. germanica.