Cloning and expression profiling of gustatory receptor genes BtabGR1 and BtabGR2 in Bemisia tabaci.
Objective: Bemisia tabaci is an important agricultural and invasive pest worldwide. Although B. tabaci has many host plants, there are differences in the tropism of B. tabaci to these different hosts. The gustatory receptor genes (GRs) play an important role in its feeding selection and other behaviors. The objective of this study is to clone the two gustatory receptor genes (GR1 and GR2) of B. tabaci, and clarify their expression profiles at different developmental stages and in different adult tissues, so as to provide a theoretical basis for further functional study of the two gustatory receptor genes. Method: The gustatory receptor genes were screened from the adult head transcriptome of B. tabaci. The open reading frame (ORF) of two gustatory receptor genes was cloned by nest PCR, and the two genes were named BtabGR1 and BtabGR2, respectively. Encoded amino acid sequence features and structure characteristics of BtabGR1 and BtabGR2 were analyzed by multiple bioinformatics methods. Phylogenetic tree between BtabGR1, BtabGR2 and other Hemiptera insects GRs was constructed using neighbor-joining method. The expression levels of the two genes at different developmental stages (egg, 1-4 instar nymphs, female and male adults), in different adult tissues (head, thorax, abdomen, leg) were detected by qRT-PCR. Result: The cDNA sequences of BtabGR1 and BtabGR2 (GenBank accession number: OL845904 and OL845905) were obtained. The complete ORFs of these two genes are 1 287 and 1 344 bp in length, encoding 428 and 447 amino acids with the predicted molecular weight of 48.54 and 51.50 kD, the isoelectric point of 8.85 and 8.74, 4 and 6 transmembrane domains. Amino acid sequence alignment and phylogenetic analysis showed that BtabGR1 and BtabGR2 were closely related to the GR28b and GR43a-like genes of other Hemiptera insects. Developmental stages expression results showed that BtabGR1 and BtabGR2 were expressed at different developmental stages of B. tabaci. The expression level of BtabGR1 in female and male adults was higher than that in other developmental stages, while BtabGR2 was highly expressed in the egg. Tissue expression results showed that BtabGR1 and BtabGR2 were expressed in different tissues of adult B. tabaci, and the two genes were both highly expressed in the head of adults. Conclusion: BtabGR1 and BtabGR2 have the typical characteristics of insect gustatory receptor genes, and both of them are highly expressed in the head of B. tabaci adults. It is speculated that these two genes play an important role in host plant adaptation of B. tabaci, and can be used as potential targets for novel control measures of B. tabaci.