Long non-coding RNAs (lncRNAs) are a diverse class of transcripts that structurally resemble mRNAs but do not encode proteins, and lncRNAs have been proven to play pivotal roles in a wide range of biological processes in animals and plants. However, knowledge of expression patterns and potential roles of honeybee lncRNA response to Nosema ceranae infection is completely unknown. Here, we performed whole transcriptome strand-specific RNA sequencing of normal midguts of Apis mellifera ligustica workers (Am7CK, Am10CK) and N. ceranae-inoculated midguts (Am7T, Am10T), followed by comprehensive analyses using bioinformatic and molecular approaches. A total of 6353 A. m. ligustica lncRNAs were identified, including 4749 conserved lncRNAs and 1604 novel lncRNAs. These lncRNAs had minimal sequence similarities with other known lncRNAs in other species; however, their structural features were similar to counterparts in mammals and plants, including shorter exon and intron length, lower exon number, and lower expression level, compared with protein-coding transcripts. Further, 111 and 146 N. ceranae-responsive lncRNAs were identified from midguts at 7-days post-inoculation (dpi) and 10 dpi compared with control midguts. Twelve differentially expressed lncRNAs (DElncRNAs) were shared by Am7CK vs. Am7T and Am10CK vs. Am10T comparison groups, while the numbers of unique DElncRNAs were 99 and 134, respectively. Functional annotation and pathway analysis showed that the DElncRNAs may regulate the expression of neighboring genes by acting in cis and trans fashion. Moreover, we discovered 27 lncRNAs harboring eight known miRNA precursors and 513 lncRNAs harboring 2257 novel miRNA precursors. Additionally, hundreds of DElncRNAs and their target miRNAs were found to form complex competitive endogenous RNA (ceRNA) networks, suggesting that these DElncRNAs may act as miRNA sponges. Furthermore, DElncRNA-miRNA-mRNA networks were constructed and investigated, the results demonstrated that a portion of the DElncRNAs were likely to participate in regulating the host material and energy metabolism as well as cellular and humoral immune host responses to N. ceranae invasion. Our findings revealed here offer not only a rich genetic resource for further investigation of the functional roles of lncRNAs involved in the A. m. ligustica response to N. ceranae infection, but also a novel insight into understanding the host-pathogen interaction during honeybee microsporidiosis.

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Here, a comparative transcriptome investigation was conducted based on high-quality deep sequencing data from the midguts of Apis cerana cerana workers at 7 d post-inoculation (dpi) and 10 dpi with Nosema ceranae and corresponding un-inoculated midguts. PCR identification and microscopic observation of paraffin sections confirmed the effective infection of A. c. cerana worker by N. ceranae. In total, 1127 and 957 N. ceranae-responsive genes were identified in the infected midguts at 7 dpi and 10 dpi, respectively. RT-qPCR results validated the reliability of our transcriptome data. GO categorization indicated the differentially expressed genes (DEGs) were respectively engaged in 34 and 33 functional terms associated with biological processes, cellular components, and molecular functions. Additionally, KEGG pathway enrichment analysis showed that DEGs at 7 dpi and 10 dpi could be enriched in 231 and 226 pathways, respectively. Moreover, DEGs in workers’ midguts at both 7 dpi and 10 dpi were involved in six cellular immune pathways such as autophagy and phagosome and three humoral immune pathways such as the Toll/Imd signaling pathway and Jak-STAT signaling pathway. In addition, one up-regulated gene (XM_017055397.1) was enriched in the NF-κB signaling pathway in the workers’ midgut at 10 dpi. Further investigation suggested the majority of these DEGs were engaged in only one immune pathway, while a small number of DEGs were simultaneously involved in two immune pathways. These results together demonstrated that the overall gene expression profile in host midgut was altered by N. ceranae infection and some of the host immune pathways were induced to activation during fungal infection, whereas some others were suppressed via host–pathogen interaction. Our findings offer a basis for clarification of the mechanism underlying the immune response of A. c. cerana workers to N. ceranae infection, but also provide novel insights into eastern honeybee-microsporodian interaction.

Nosema ceranae is a widespread fungal pathogen of honeybees, which is infective to all castes in the colony, including queens, drones and workers. Nosemosis caused by N. ceranae poses a big challenge for apiculture all over the world. Here, midguts of normal and N. ceranae-infected Apis cerana cerana workers at 7 and 10 days post infection were sequenced utilizing small RNA sequencing (sRNA-seq) technology. Totally, more than 150.54 Mb raw reads were produced in this article, and over 144.26 Mb high-quality clean reads with a mean ratio of 95.83% were obtained after strict filtering and quality control. For more insight please see “Comparative identification of microRNAs in Apis cerana cerana workers' midguts responding to Nosema ceranae invasion” (Chen et al., 2019). Raw data are available in NCBI Sequence Read Archive (SRA) database under the BioProject number PRJNA487111. Our data can be used for investigating differentially expressed microRNAs (miRNAs) and piRNAs and their regulatory roles engaged in A. c. cerana response to N. ceranae infection, and for offering potential candidates for uncovering the molecular mechanisms regulating eastern honeybee-microsporidian interactions.

Long non-coding RNAs (lncRNAs) are a diverse class of transcripts that structurally resemble mRNAs but do not encode proteins, and lncRNAs have been proved to play pivotal roles in a wide range of biological processes in animals and plants.However, knowledge of expression pattern and potential role of honeybee lncRNAs response to Nosema ceranae infection is completely unknown. Here, we performed whole transcriptome strand-specific RNA sequencing of normal midguts of Apis mellifera ligustica workers (Am7CK, Am10CK) and N. ceranae-inoculated midguts (Am7T, Am10T), followed by comprehensive analyses using bioinformatic and molecular approaches. A total of 6353 A. m. ligustica lncRNAs were identified, including 4749 conserved lncRNAs and 1604 novel lncRNAs. These lncRNAs had low sequence similarities with other known lncRNAs in other species; however, their structural features were similar with counterparts in mammals and plants, including shorter exon and intron length, lower exon number, and lower expression level, compared with protein-coding transcripts. Further, 111 and 146 N. ceranae-responsive lncRNAs were identified from midguts at 7 day post inoculation (dpi) and 10 dpi compared with control midguts. 12 differentially expressed lncRNAs (DElncRNAs) were shared by Am7CK vs Am7T and Am10CK vs Am10T comparison groups, while the numbers of unique ones were 99 and 134, respectively. Functional annotation and pathway analysis showed the DElncRNAs may regulate the expression of neighboring genes by acting in cis. Moreover, we discovered 27 lncRNAs harboring eight known miRNA precursors and 513 lncRNAs harboring 2257 novel miRNA precursors.Additionally, hundreds of DElncRNAs and their target miRNAs were found to form complex competitive endogenous RNA (ceRNA) networks, suggesting these DElncRNAs may act as miRNA sponges. Furthermore, DElncRNA-miRNA-mRNA networks were constructed and investigated, the result demonstrated that part of DElncRNAs were likely to participate in regulating the material and energy metabolism as well as cellular and humoral immune during host responses to N. ceranae invasion.Finally, the expression pattern of 10 DElncRNAs was validated using RT-qPCR, confirming the reliability of our sequencing data. Our findings revealed here offer not only a rich genetic resource for further investigation of the functional roles of lncRNAs involved in A. m. ligustica response to N. ceranae infection, but also a novel insight into understanding host-pathogen interaction during microsporidiosis of honeybee.