Abstract: 【Aim】This study aims to explore the expression patterns of the aryl hydrocarbon receptor (AHR) gene AmAHR and the aryl hydrocarbon receptor nuclear translocator (ARNT) gene AmARNT in Apis mellifera during the growth and development of workers and under insecticide stress, providing theoretical references for the functional research of these two genes. 【Methods】The full-length coding sequences (CDSs) of AmAHR and AmARNT of A. mellifera were obtained through gene cloning, and homologous sequence alignment and phylogenetic tree construction were conducted among multiple species. The expression levels of AmAHR and AmARNT in different developmental stages of workers (egg, larva, pupa and adult), tissues of the 8-day-old adult workers (antenna, hypopharyngeal gland, foreleg, midleg, hindleg, wing, midgut, hindgut and stinger, as well as the head, thorax and abdomen with the aforementioned tissues removed), and the adult head of the 8-day-old workers of A. mellifera after oral administration of the insecticides lambda-cyhalothrin (1.25, 2.5, 5 and 10 mg/L), tau-fluvalinate (30, 60, 120 and 240 mg/L) and formic acid (1.25, 2.5, 5 and 10 mg/L), respectively, were detected by qRT-PCR. 【Results】The cloned CDSs of AmAHR and AmARNT of A. mellifera encoded 885 and 686 amino acids, respectively, and the encoded proteins contained one helix-loop-helix, two PAS domains and one PAC domain, belonging to hydrophilic intracellular proteins. The top 23 origin species of the homogeneous proteins with highly consistent amino acid sequences with AmAHR and AmARNT all belonged to the order Hymenoptera, and AmAHR and AmARNT clustered with their corresponding AHRs and ARNTs from the insects of the genus Apis. During the development from egg to adult, the expression level of AmAHR exhibited a unimodal pattern, peaking at the white-eyed white pupal stage, with the expression level significantly higher than those at the other developmental stages, and being 37.860fold as high as that at the egg stage. The expression level of AmARNT exhibited a bimodal pattern, with peak levels observed in eggs and the 3-day-old prepupae. The peak expression periods of AmAHR and AmARNT during pupal development were adjacent, with the expression level of AmARNT reaching its maximum before that of AmAHR. The expression level of AmAHR in the antenna of the 8-day-old adult workers was the highest, being 34.08-fold as high as that in the head, and was significantly higher than those in the other tissues. The expression level of AmARNT in the thorax of the 8-day-old adult workers was significantly higher than those in the other tissues, being 1.75-fold as high as that in the head. The expression level of AmAHR in the head of the 8-day-old adult workers fed with 15 μL of 5 mg/L lambda-cyhalothrin was significantly upregulated to 1.83-fold and those in the head of the 8-day-old adult workers fed with 30 and 60 mg/L tau-fluvalinate was upregulated to 1.63- and 1.74-fold, respectively, as compared with those of the control group. In contrast, the expression level of AmAHR in the head of the 8-day-old adult workers fed with 120 mg/L tau-fluvalinate was only 0.36-fold as high as that of the control group, indicating that the expression of AmAHR was suppressed. The expression levels of AmAHR in the head of the 8-day-old adult workers fed with 1.25, 2.5 and 5 mg/L formic acid were upregulated to 4.13-, 3.61- and 2.56-fold, respectively, as compared with those of the control. The expression levels of AmARNT in the head of the 8-day-old adult workers fed with 2.5 and 10 mg/L lambda-cyhalothrin, and 30 and 120 mg/L tau-fluvalinate were significantly downregulated to 0.69-, 0.68-, 0.60- and 0.34-fold, respectively, as high as that of the control, whereas 2.5 mg/L formic acid feeding upregulated the expression level of AmARNT to 1.68-fold compared to the control.【Conclusion】 The evolutionary relationships of AmAHR and AmARNT in A. mellifera are relatively conserved compared to those in other insect species. The synchronous expression peaks of AmAHR and AmARNT during the initial pupal stage suggest a close correlation in their expression patterns, which may be related to the prepupal development of workers. After exposure to two pyrethroid insecticides, AmAHR and AmARNT both exhibited identical expression trends, in contrast to their responses to formic acid. This difference is likely associated with distinct detoxification metabolism mechanisms between these two types of pesticides. This study provides a new theoretical basis for further investigation into the functions of AHR and ARNT in insects.

Key words: Apis mellifera, aryl hydrocarbon receptor, aryl hydrocarbon receptor nuclear translocator, gene cloning, spatiotemporal expression profiling, pesticide stress