Circular RNAs (circRNAs) are a new class of non-coding RNAs, which have been confirmed to regulate insect gene expression and immune response through multiple manners such as competing endogenous RNA (ceRNA) regulatory network. Currently, function of circRNA in honey bee immune response remains unclear. In this study, PCR and Sanger sequencing were performed to validate the back splicing (BS) site of ame_circ_000115 (in short ac115). RT-qPCR was used to detect the expression profile of ac115 in larval guts of Apis mellifera ligustica stressed by Ascosphaera apis. Dual-luciferase reporter gene assay was conducted to verify the binding relationship between ac115 and ame-miR-13b. Interference of ac115 in larval guts was carried out by feeding specific siRNA, followed by determination of the effect of ac115 interference on expression of six genes relevant to host immune response. The results confirmed the existence of BS site within ac115. Compared with the un-inoculated group, the expression of ac115 in 4-day-old larval gut of the A. apis-inoculated group was up-regulated with extreme significance (P < 0.000 1), while that in 5- and 6-day-old larval guts were significantly up-regulated (P < 0.05). The brightness of specific band for ac115 in 4-, 5- and 6-day-old larval guts of the siRNA-circ_000115-fed group gradually became weak, whereas that of the siRNA-scrambl-fed group was pretty high without obvious variation. Compared with that of the siRNA-scramble-fed group, the expression of ac115 in 4-day-old larval gut of the siRNA-circ_000115-fed group was significantly down-regulated (P < 0.05), whereas that of the 5- and 6-day-old larval guts were down-regulated with extreme significance (P < 0.001). Ame-miR-13b was truly existed and expressed in A. m. ligustica larval guts, and there was true binding relationship between ac115 and ame-miR-13b. Compared with that of the siRNA-scramble-fed group, the expression of antimicrobial peptide genes hymenoptaecin and abaecin in 6-day-old larval gut of the siRNA-circ_000115-fed group was significantly up-regulated (P < 0.05), while that of ecdysone receptor (Ecr) was down-regulated with extreme significance (P < 0.01). These results indicate that ac115 is truly expressed in A. m. ligustica larval guts, BS site truly exists within ac115, and effective interference of ac115 in A. m. ligustica larval guts can be achieved via feeding siRNA. Moreover, ac115 potentially regulates Ecr expression through adsorption of ame-miR-13b and expression of hymenoptaecin and abaecin using a non-ceRNA manner, further participating in host stress-response.
Bees/genetics* ; Animals ; Larva/metabolism* ; RNA, Circular/genetics* ; RNA, Small Interfering/genetics* ; MicroRNAs/genetics*

In nature, honeybees are the most important pollinators. They play a vital role in both protecting the diversity of natural ecosystems, and maintaining the yield-improving effects of agroecosystems. But in recent years, epidemic disease in bees has caused huge losses. Black Queen Cell Virus (BQCV) is a bee pathogen that was first reported in 1955. It mainly infects bee larvae and pupae, making their bodies turn dark and black, and causing a massive decrease in the bee population. More specifically, the virus makes the exterior of the cell walls in the larvae and pupae turn black. BQCV is a seasonal epidemic, spread by means horizontal and vertical transmission, and is often unapparent. BQCV not only infects a variety of bee species, but also spiders, centipedes and other arthropods. It can also be coinfected with other honeybee viruses. In recent years, research has shown that the Nosema intestinal parasite plays an important role in BQCV transmission and bees carrying Nosema that become infected with BQCV have increased mortality. Here we summarize current research on the incidence, prevalence, geographical distribution and transmission of BQCV.
Animals ; Bees ; virology ; Dicistroviridae ; classification ; genetics ; isolation & purification ; physiology ; Insect Viruses ; classification ; genetics ; isolation & purification ; physiology

Acarapis mites, including Acarapis woodi, Acarapis externus, and Acarapis dorsalis, are parasites of bees which can cause severe damage to the bee industry by destroying colonies and decreasing honey production. All 3 species are prevalent throughout many countries including UK, USA, Iran, Turkey, China, and Japan. Based on previous reports of Acarapis mites occurring in northeast Asia, including China and Japan, we investigated a survey of Acarapis mite infestations in honey bees in Korean apiaries. A total of 99 colonies of Apis mellifera were sampled from 5 provinces. The head and thorax of 20 bees from each colony were removed for DNA extraction. PCR assays were performed with 3 primer sets, including T, A, and K primers. Results indicated that 42.4% (42/99) of samples were Acarapis-positive by PCR assay which were sequenced to identify species. Each sequence showed 92.6-99.3% homology with reference sequences. Based on the homology, the number of colonies infected with A. dorsalis was 32 which showed the highest infection rate among the 3 species, while the number of colonies infected with A. externus and A. woodi was 9 and 1, respectively. However, none of the Acarapis mites were morphologically detected. This result could be explained that all apiaries in the survey used acaricides against bee mites such as Varroa destructor and Tropilaelaps clareae which also affect against Acarapis mites. Based on this study, it is highly probable that Acarapis mites as well as Varroa and Tropilaelaps could be prevalent in Korean apiaries.
Animals ; Bees/*parasitology ; Mites/classification/*genetics/physiology ; Molecular Sequence Data ; Phylogeny ; Prevalence ; Republic of Korea

Honeybee pupae were collected from Jilin apiaries and RNA was extracted for use as a tefnplate for amplification. Based on the complete genome sequences of black queen cell virus (BQCV) published on GenBank, we designed 10 pairs of primers to amplify genes by reverse transcription-polymerase chain reaction (RT-PCR). Using this approach, we have obtained the first complete genome sequence of a BQCV isolate in China. The genome of the isolated strain, named BQCV-JL1, is composed of 8358 nucleotides and shares between 86% and 93% homology with the complete genome sequences of the other six BQCV strains published on GenBank. ORF 1 of BQCV-JL1 is positioned between nucleot ides (nt) 546 and 4676 (4131 nt), while ORF 2 is located between nt 5750 and 8203. Between the two ORFs of BQCV-JL1 there is a short ORF, called ORF 3, between nt 4891 and 5433 (543 nt). The first functional gene ex- pression domain of the BQCV-JL1 strain is positioned between nt 546 and 5 429, encompassing both ORF 1 and ORF 3. There is an internal ribosome entry site (IRES) located before ORF 2, the last three bases of which are CCU (nt 5642-5644). These bases act as an initiation.codon facilitating the translation of ORF 2. The second functional gene expression domain of the BQCV-JL1 strain is located between nt positions 5642 and 8203. The BQCV-JL1 strain was found to share high sequence identity (93%) with the Hungary 10 genotype at the whole-genome level and analysis of the nucleotide and amino acid sequences revealed that the BQCV-JL1 strain also shows close genetic relationships with the South Korea strain, suggesting that both the BQCV-JL1 and South Korea strains may have migrated from European countries. BQCV-JL1 strain was different from the other 6 strains in dividing the nucleotides positions of QRF, which vqs because of the gene mutation.
Amino Acid Sequence ; Animals ; Bees ; China ; Genome, Viral ; Molecular Sequence Data ; Open Reading Frames ; Phylogeny ; RNA Viruses ; classification ; genetics ; isolation & purification ; Viral Proteins ; genetics