Abstract: 【Aim】 Ionotropic receptors (IRs) are crucial for insects’ olfactory, gustatory, temperature, and humidity sensing capabilities. This study aims to identify the IR gene family in Bactrocera dorsalis at the whole-genome level combined with transcriptome data, so as to provide a theoretical basis for further research on the functions of ionotropic receptor genes in B. dorsalis. 【Methods】 IR genes in the whole genome of B. dorsalis were identified by using hidden Markov models, multiple sequence alignments, gene domain analysis, and phylogenetic analysis. Chromosomal localization, full-length gene structure, protein conserved motifs, and collinearity analysis of IR gene family were examined by using TBtools. Evolutionary pressures were assessed with EasyCodeML. Hisat2 and Stringtie software was employed to quantify and analyze the expression patterns of IR genes in the peripheral nervous tissues (antenna, mouthparts, foreleg, midleg, hindleg, and genitalia) of B. dorsalis. qPCR was used for verification. 【Results】 A total of 39 candidate IR genes were identified within the whole genome of B. dorsalis. All the above candidate IR genes were located on autosomes, with 26 of them having complete full-length CDS structures supported by transcriptomic evidence. These full-length IR genes shared 2-8 identical protein conserved motifs, reflecting their structural conservation. Twenty-eight candidate IR genes were demonstrated the collinearity with those of other true flies in the genus Bactrocera, and one IR gene was found to be under strong negative selection. Seventeen candidate IR genes with collinearity were expressed in the peripheral nervous tissues of B. dorsalis, among them, 10 IR genes were exclusively expressed in the antennae, two IR genes only expressed in the mouthparts, and one IR gene solely expressed in the ovipositor. Additionally, one IR gene was expressed only in the antennae and male genitalia, one IR gene was expressed across the tissues except for the ovipositor, two IR genes were expressed across all peripheral nervous tissues, six IR genes were expressed differentially between female and male, and the remaining 11 candidate IR genes showed no expression in peripheral nervous tissues. 【Conclusion】 In this study we systematically identified the IR gene family in B. dorsalis using genomic and transcriptomic data. We analyzed the structural features, evolutionary relationships, and expression patterns of the IR gene family members, providing a theoretical foundation for further functional studies on the IR genes of B. dorsalis.

Key words: Bactrocera dorsalis；ionotropic receptor；genome-wide identification, gene characteristics, phylogeny, evolution