Abstract: 【Objective】 The objective of this study is to de novo assemble a reference transcriptome for Apis cerana cerana larval gut, perform gene function and pathway annotation for this transcriptome, and to identify specific SSR molecular markers for A. c. cerana larvae. 【Method】 3-day-old instar A. c. cerana larvae were fed with the purified Ascosphaera apis spores, the guts of 4-, 5- or 6-day-old honeybee larvae were sampled and used as sequencing material for RNA seq. After filtration, clean reads were obtained, and unigenes were assembled using Trinity software. BLASTX tool (E-value＜10⁻⁵) was used to search the unigenes against NCBI Nr, Swiss-Prot protein, KOG as well as KEGG databases to perform gene function and pathway annotation. MISA software was used to search microsatellite markers in the larval gut’s transcriptome. The specific primers of all SSRs were designed using Primer Premier 5 program and several pairs were used to amplify SSR loci in A. c. cerana larvae samples from 3 different regions (Beijing, Xingcheng, and Chengdu) in China by method of PCR. 【Result】 In this study, RNA seq produced 35 670 000 high quality reads, which were assembled into 43 557 unigenes with a mean length of 898 nt. 18 225 unigenes were annotated in the public protein databases. a total of 11 442 unigenes had a KOG classification and they distributed in 25 KOG categories, among them, RNA processing and modification was the largest group (1 249). 9 679 unigenes could be classified into three gene ontology (GO) categories, in which the mostly enriched ones were cellular process (4 201 unigenes), cell (2 900 unigenes) and binding    (4 935 unigenes). 4 517 unigenes were annotated to 216 KEGG pathways, among them, ribosome (385 unigenes) was the largest. Finally, 13 448 SSRs were found in 7 763 unigenes, and 6 out 20 SSR loci could be successfully amplified in A. c. cerana larvae samples from 3 different regions in China using PCR. 【Conclusion】 This study assembled and annotated a reference transcriptome for A. c. cerana larval gut, which will provide a key information not only to studies on eastern honeybee and its larvae such as molecular biology and omics, but also to improve and validate the genome of A. cerana. SSR markers developed here could be applied to future investigation of A. c. cerana including gene map construction, genetic diversity analysis as well as gene location. Meanwhile, this study suggested that developing molecular markers using transcriptome data of non-model organism is a rapid and efficient method.

Key words: RNA seq; de novo assembly, Apis cerana cerana, unigenes, SSR