Abstract: To explore the pattern of methylation in the Chinese honeybee, Apis cerana cerana, the DNA methyltransferase 3 (Dnmt3) gene in A. cerana cerana was cloned by using RT-PCR, and the quantitative analysis of the expression level of Dnmt3 mRNA in different developmental stages of worker (4 d-old pupa, 1, 7 and 30 d-old workers, and laying worker) and queen (4 d-old pupa, 1 d-old queen and laying queen) were conducted using real-time qPCR. The full-length cDNA of Dnmt3 gene (GenBank accession no. JQ740768) is 2 277 bp, encoding 758 amino acids, and the predicted MW and pI are 88.24 kD and 7.85, respectively. Based on the comparison of the domain and the phylogenetic tree of the amino acids of Dnmt3 in A. cerana cerana and other species, the sequence obtained has up to 99% identity with that of A. mellifera. The Dnmt3 transcript was clearly detected in different developmental stages of worker and queen, and it was expressed significantly higher in 30 d-old worker than in 1 d- and 7 d-old worker (P<0.05), while no difference existed between 1 d- and 7 d-old worker (P>0.05). The Dnmt3 transcript was expressed higher in queen pupae than in worker pupae (P<0.05), and was higher in 1 d-old queen than in 1 d-old worker (P<0.05). The expression level of Dnmt3 gene between laying worker and laying queen had no significant difference. The results suggested that Dnmt3 may be involved in the division of labor in workers and ovary development in honeybees.

Key words: Apis cerana cerana, DNA methylation, DNA methyltransferase, gene cloning, sequence analysis, expression profiling