Abstract: 【Aim】 This study aims to uncover the function of ace-miR-3720 in the larval gut development of Apis cerana cerana workers and provide theoretical and experimental bases for further investigation of the regulation mechanism of ace-miR-3720 underlying the development of larval gut. 【Methods】 According to the nucleotide sequence of ace-miR-3720, the corresponding mimic (mimic-miR-3720) and inhibitor (inhibitor-miR-3720) were designed and synthesized, and used to feed larvae of A. cerana cerana workers to perform overexpression and knockdown of ace-miR-3720, respectively. The relative expression levels of ace-miR-3720 and its target genes CKⅠ, MAPK1 and βGBP1 in the 4-6-day-old larval guts after overexpression and knockdown of ace-miR-3720 were detected using RT-qPCR. The larval guts after overexpression and knockdown of ace-miR-3720 were weighed using analytical balance. 【Results】The expression levels of ace-miR-3720 in the 4- and 5-day-old larval guts in the mimic-miR-3720 group were extremely significantly up-regulated, while that in the 6-day-old larval gut was significantly up-regulated, as compared to those in the nonsense mimic (mimic-NC) group. The expression level of ace-miR-3720 in the 4-day-old larval gut in the inhibitor-miR-3720 group was extremely significantly down-regulated, whereas those in the 5- and 6-day-old larval guts were significantly down-regulated, as compared to those in the nonsense inhibitor (inhibitor-NC) group. There is a potential targeting relationship between ace-miR-3720 and genes CKⅠ, MAPK1 and βGBP1. In the mimic-miR-3720 group, the expression levels of CKⅠ in the 4- and 5-day-old larval guts were extremely significantly down-regulated, while that in the 6-day-old larval gut was significantly down-regulated; the expression level of MAPK1 in the 4-day-old larval gut was significantly down-regulated, whereas those in the 5- and 6-day-old larval guts were extremely significantly down-regulated; the expression level of βGBP1 in the 4-day-old larval gut was significantly down-regulated, while those in the 5- and 6-dayold larval guts were extremely significantly down-regulated; additionally, the weight of the 4- and 5-day-old larval guts in the mimic-miR-3720 group was extremely significantly decreased, whereas that of the 6-day-old larval gut was significantly decreased, as compared with those in the mimic-NC group. In the inhibitor-miR-3720 group, the expression levels of CKⅠ in the 4-6-day-old larval guts were extremely significantly up-regulated; the expression level of MAPK1 in the 4-day-old larval gut was significantly up-regulated, while those in the 5 and 6-day-old larval guts were extremely significantly up-regulated; the expression levels of βGBP1 in the 4- and 6-day-old larval guts were significantly up-regulated, whereas that in the 5-day-old larval gut was extremely significantly up-regulated; in addition, the weight of the 4- and 6-day-old larval guts was significantly increased, while that of the 5-day-old larval gut was extremely significantly increased, as compared with those in the inhibitor-NC group. 【Conclusion】 ace-miR-3720 truly exists in the larval gut of A. cerana cerana workers. Effective overexpression and knockdown of miRNAs in the larval gut of A. cerana cerana could be achieved by feeding with mimic and inhibitor, respectively. ace-miR-3720 may affect the weight of larval guts of A. cerana cerana workers and participate in larval gut development through regulation of the expression of CKⅠ, MAPK1 and βGBP1.

Key words: Apis cerana cerana, larva, gut, microRNA, ace-miR-3720, target gene, overexpression, knockdown