Molecular characterization of sugar taste receptors in the cotton bollworm Helicoverpa armigera

Insects utilize sugars as their essential energy and nutrient sources; therefore, the sense of sugar detection plays a critical role in insect behaviours. Previously, using genomic and transcriptomic approaches, we identified eight putative sugar gustatory receptor (GR) genes from the cotton bollworm Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae). Here, we further validated these annotated sugar receptor genes (HarmGr4-HarmGr8 and HarmGr10-HarmGr12) and found HarmGr10 may be a pseudogene carrying a stop codon in the open reading frame. Sequence alignment revealed H. armigera sugar GR sequences are conserved at C-terminus and phylogenetic analysis showed that insect sugar GRs have evolved in a family-specific manner. Interestingly, all eight H. armigera sugar GRs are localized in a tandem array on the same scaffold of the genome. In silico gene expression and reverse transcription (RT)-PCR analysis showed that HarmGr10 is specifically expressed in male adult testes while HarmGr11 is specifically expressed in female adult ovaries, suggesting H. armigera sugar GRs may be involved in reproductionrelated functions. This study improves our knowledge on insect sugar receptors and gustatory systems.