Abstract: 【Aim】 The aim of this study is to clone and analyze circadian clock gene Double-time (Dbt) in Helicoverpa armigera, and to examine the diurnal expression pattern of Dbt mRNA levels and its determinants, so as to provide a theoretical basis for studying the mechanisms of action of the circadian clock genes in the compound eyes and understanding the function of circadian clock genes in peripheral tissues in noctuid moths. 【Methods】 Dbt was cloned from compound eyes of 2-day-old female adults of H. armigera by RT-PCR and RACE, and its deduced amino acid sequence was analyzed using online sites and software. The expression levels of Dbt among different tissues (head, brain, compound eyes, antennae, thorax, abdomen, leg and wing) of female and male adults were determined and compared by qPCR. The diurnal changes of Dbt mRNA levels in compound eyes and head were measured under a photoperiod of14L∶10D and constant darkness (DD). The 2-day-old adults were irradiated by sensitive wavelength of UV, blue and green lights, respectively, for 6 h from the beginning of the scotophase, and the changes in the expression levels of Dbt in compound eyes were determined after light exposure. Female and male adults were paired for mating during scotophase, and the changes in the expression levels of Dbt in compound eyes were determined at 0 h and 3 h after copulation, respectively. 【Results】 The full-length cDNA of Dbt gene was cloned from the compound eyes of H. armigera and designated as HeDbt (GenBank accession number: KM233159). It has a 1 026 bp open reading frame encoding a predicted protein of 314 amino acids, with a molecular mass of 39.79 kD and a calculated isoelectric point (pI) of 9.55. Its deduced amino acid sequence has no transmembrane topologies, and shares several typical conserved domains of insect DBT. HeDBT shows a high homology with DBT proteins from Spodoptera exigua (99% amino acid sequence identity) and Antheraea pernyi (97% amino acid sequence identity). qPCR results illustrated that HeDbt was expressed in all the tested adult tissues, and had low expression levels in the head, brain and compound eyes and high expression levels in thorax and abdomen. The expression of HeDbt showed no obvious circadian rhythm in both the head and compound eyes under14L∶10D and DD. The expression of HeDbt was down-regulated in compound eyes after light exposure and copulation, but with similar HeDbt mRNA levels between female and male adults. 【Conclusion】 A circadian clock gene HeDbt was successfully cloned from H. armigera. HeDbt had low mRNA levels in the head and compound eyes of H. armigera adults. Its expression in the head and compound eyes showed no obvious circadian rythym, but was influenced by light exposure and copulation of adults. Our study provides a theoretical basis for further studying the function of circadian clock genes in peripheral tissues in noctuid moths.

Key words: Helicoverpa armigera, circadian clock gene, compound eyes, photoreceptor, peripheral tissue, circadian rhythm