Abstract: 【Aim】 The head is the centre controlling physiological behavior in bumblebees, and micro-RNAs (miRNAs) are involved in the regulation of this behavior. We compared the miRNA expression between the heads of egg-laying and non-egg-laying queens of the bumblebee Bombus lantschouensis so as to clarify the roles of miRNAs in queen head during oviposition.【Methods】 miRNAs in heads of egg-laying and non-egg-laying queens of B. lantschouensis were sequenced by Solexa. Bioinformatics software was used to identify the miRNA and its target genes. qPCR was used to verify the significantly differentially【Results】 Cleaned data showed 14 228 864 reads from heads of egg-laying queens and 21 431 031 reads from heads of non-egg-laying queens. The length of the reads ranged from 19 to 24 nt, and the 22 nt sequences of miRNAs were the most abundant in egg-laying and non-egg-laying queen heads, accounting for 45.8% and 45.1% of their samples, respectively. A total of 297 miRNA sequences were identified from the queen heads. Among them, 270 miRNAs were known and 27 were novel by comparison with the miRBase database. Of the known sequences, 92 miRNAs were known from the honeybee, and 178 miRNAs known from other animals. Within the known 92 miRNAs from the honeybee, there were 91 miRNAs in the head of egg-laying queens and 90 in the head of non-egg-laying queens. For the novel miRNAs, there were 22 miRNAs in the head of egg-laying queens and 25 in the head of non-egg-laying queens, respectively. Expression analysis showed that eight miRNAs reached significantly different expression levels in the heads of egg-laying and non-egg-laying queens (P<0.01). qPCR demonstrated that the eight significantly differentially expressed miRNAs existed in the bumblebee. The target genes for the top three miRNAs with significantly different expression levels were predicted, and it was found that nine target genes were co-regulated by the three miRNAs. All of the target genes are related to GTP binding and transcriptional regulation. 【Conclusion】 This is the first exploration of miRNA within bumblebees by high-throughput sequencing technology. Different miRNA expression levels are demonstrated between the heads of egg-laying and non-egg-laying queens. Our results may contribute to understanding the function of miRNAs and their roles in bumblebees.

Key words: Bombus lantschouensis, queen, miRNA, Solexa sequencing, egg-laying, bioinformatics analysis