Abstract: 【Aim】The transcriptome database of the proboscis of Apis mellifera ligustica workers was established to identify gustatory receptor (GR) gene information through functional annotation and explore the correlation between GR genes and the foraging preferences of A. m. ligustica.【Methods】The proboscis of A. m. ligustica workers collecting pear pollen, collecting rapeseed pollen and without collecting pollen were subjected to transcriptome sequencing using the Illumina HiSeq high-throughput sequencing platform, followed by screening, GO functional annotation and KEGG metabolic pathway classification of differentially expressed genes (DEGs), screening of GR genes and construction of phylogenetic tree. The qRT-PCR was used to validate the expression of nine DEGs.【Results】A total of 342 DEGs were identified, with 157 up-regulated and 185 down-regulated. The GO functional annotation results indicated that these DEGs were predominantly involved in cellular processes, cellular anatomical entities and binding. KEGG metabolic pathway analysis demonstrated that DEGs were the most significantly enriched in the oxidative phosphorylation pathway, followed by in the tyrosine metabolism pathway. Within the transcriptome of proboscis of A. m. ligustica workers, a total of nine GR genes were identified. Specifically, four of these nine genes were previously identified as GR genes, and the remaining five genes were unknown GR genes identified in this study. All these genes have intact open reading frames and contain seven transmembrane domains typically observed in the insect GR gene family. The phylogenetic tree, constructed based on the amino acid sequences of AmelGRs of A. m. ligustica and GRs of Drosophila melanogaster, indicated that AmelGR4 and AmelGR6 probably belong to the bitter taste receptor family, whereas AmelGR9 may be linked to the sweet taste receptor family. The qRT-PCR verification results confirmed that the expression patterns of eight of the nine selected DEGs in the proboscis of workers collecting pear pollen were in accordance with the RNA-seq results. Moreover, all the nine DEGs in the proboscis of workers collecting rapeseed pollen showed expression patterns consistent with the RNA-seq results.【Conclusion】 In this study, we acquired the transcriptome data from the proboscis of A. m. ligustica workers and screened GR genes. The phylogenetic analysis suggests that AmelGR4 and AmelGR6 likely belong to the bitter taste receptor family, while AmelGR9 may belong to the sweet taste receptor family. It is hypothesized that the foraging preference of A. m. ligustica could be related to GR genes. These research findings enhance our understanding of insect gustatory perception system at the molecular level and provide a foundation for investigating the regulatory mechanism underlying foraging preference behavior of A. m. ligustica during pollination.

Key words: Apis mellifera ligustica, proboscis, transcriptome sequencing, gene functional annotation, gustatory receptor gene