In-depth investigation of microRNA-mediated cross-kingdom regulation between Asian honey bee and microsporidian

Abstract Asian honey bee Apis cerana is the original host for Nosema ceranae , a unicellular fungal parasite that causes bee nosemosis throughout the world. Currently, interaction between A. cerana and N. ceranae is largely unknown. Here, based on our previously gained high-quality RNA-seq and small RNA-seq data from N. ceranae -infected A. c. cerana workers’ midguts and clean spores, differentially expressed mRNAs (DEmiRNAs) in N. ceranae targeted by DEmiRNAs in host midguts and A. c. cerana DEmRNAs targeted by microsporidian DEmiRNAs were predicted using bioinformatics, and then target DEmRNAs in microsporidian and host were annotated and investigated, with a focus on targets involved in N. ceranae glycolysis/glyconeogenesis and virulence factors as well as A. c. cerana energy mechanism and immune response. It’s found that 97 down-regulated (60 up-regulated) mRNAs in NcCKM vs NcTM1 were potentially targeted by eight up-regulated (six down-regulated) miRNAs in AcCKMI1 vs AcTMI1, 44 down-regulated (15 up-regulated) mRNAs in NcCKM vs NcTM2 were putative targets of seven up-regulated (two down-regulated) miRNAs in AcCKMI2 vs AcTMI2. Additionally, miR-60-y and miR-676-y were found to up-regulate in AcCKMI1 vs AcTMI1 and target genes engaged in spore wall protein and glycolysis/gluconeogenesis, while miR-60-y in AcCKMI1 vs AcTMI1 was up-regulated and potentially targeted a glycolysis/gluconeogenesis-associated gene. Comparatively, 343 down-regulated (138 up-regulated) mRNAs in AcCKM1 vs AcTM1 were putative targets of 121 up-regulated (112 down-regulated) miRNAs in NcCKMI vs NcTMI1, 247 down-regulated (110 up-regulated) mRNAs were putatively targeted by 110 up-regulated (104 down-regulated) miRNAs in NcCKMI vs NcTMI2. Further analysis showed that 31 up-regulated miRNAs in NcCKMI vs NcTMI1 potentially targeted 12 down-regulated mRNAs in AcCKM1 vs AcTM1, which were involved in five immune-related pathways such as phagasome and Jak-STAT signaling pathway, whereas nine up-regulated miRNAs in NcCKMI vs NcTMI2 putatively targeted five down-regulated mRNAs in AcCKM2 vs AcTM2, which were engaged in three immune-related pathways including endocytosis, lysosomes, and regulation of autophagy. In addition, miR-21-x was observed to up-regulate in NcCKMI vs NcTMI1 and target a oxidative phosphorylation-related gene. Finally, potential targeting relationship between two host DEmiRNAs-microsporidian DEmRNAs pairs and two microsporidian DEmiRNAs-host DEmRNAs pairs were verified on basis of RT-qPCR. Our findings not only lay a foundation for exploring the molecular mechanism underlying cross-kingdom regulation between A. c. cerana workers and N. ceranae , but also offer valuable insights into Asian honey bee-microsporidian interaction.