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Updated: Jan 27, 2026
RNAi-mediated Double Gene Knockdown and Gustatory Perception Measurement in Honey Bees Apis mellifera
Published on: July 25, 2013
Ascosphaera apis-derived microRNA-like RNAs mediate cross-kingdom regulation of gene expression in western honeybee
Xiaoxue Fan1, Nian Fan2, Tao Wu2
1College of Bee Science, Fujian Agriculture and Forestry University, Fuzhou 350002, Fujian, China; National and Local United Engineering Laboratory of Natural Biotoxin, 350002 Fuzhou, Fujian, China; Apitherapy Research Institute of Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian, China.
Abstract:
Chalkbrood fungus Ascosphaera apis (A. apis) produces miRNA-like small RNAs (milRNAs) that may modulate honey bee (Apis mellifera) larval biology through cross-kingdom RNA interference (ckRNAi). We identified 380, 106, 107, and 110 highly expressed milRNAs (HmilRNAs) in pure spores and infected larval guts at days 4, 5, and 6, respectively. Eighteen HmilRNAs were conserved across all groups, forming a complex regulatory network predicted to target 188 host genes (6,057 mRNAs) associated with critical signaling pathways, including Wnt, Hippo, mTOR, MAPK, and Toll/Imd. Among these, aap-milR-11980-x was validated to directly target the ecdysone-inducible gene E75 and the transcriptional repressor tramtrack (TTK). Dual-luciferase assays confirmed that aap-milR-11980-x represses these targets via specific binding to their 3'-UTR. In vivo modulation of aap-milR-11980-x in 6-day-old larval guts using agomirs and antagomirs successfully altered E75, TTK, and antimicrobial peptide (AMP) transcript levels. However, despite significant molecular regulation, no statistically significant difference in larval survival was observed between treatment groups (P > 0.05). This discrepancy suggests that while aap-milR-11980-x effectively rewires host gene expression, its primary function may be to induce sub-lethal physiological changes, such as developmental delay or immune modulation, rather than acute lethality. These findings indicate that A. apis HmilRNAs fine-tune host cellular responses, potentially to extend the temporal window for fungal development or resource acquisition, highlighting a sophisticated layer of molecular manipulation in the A. apis-honey bee interaction.
Insights
The chalkbrood fungus Ascosphaera apis uses small RNAs to alter honey bee larval gene expression, but without causing significant changes in survival. This suggests the fungus manipulates host biology for its own benefit, not acute lethality.
Area of Science:
- Mycology
- Entomology
- Molecular Biology
Background:
- Chalkbrood disease, caused by Ascosphaera apis, impacts honey bee populations.
- Honey bee larvae are susceptible to A. apis infection.
- Cross-kingdom RNA interference (ckRNAi) is a potential mechanism for host-pathogen interaction.
Purpose of the Study:
- To investigate the role of miRNA-like small RNAs (milRNAs) from A. apis in modulating honey bee larval biology.
- To identify specific milRNAs and their host targets involved in the A. apis-honey bee interaction.
- To understand the functional consequences of ckRNAi by A. apis milRNAs on honey bee larvae.
Main Methods:
- Identification and quantification of highly expressed milRNAs (HmilRNAs) in A. apis spores and infected larval guts.
- Bioinformatic prediction of HmilRNA targets in the honey bee genome.
- Validation of HmilRNA-target interactions using dual-luciferase assays.
- In vivo manipulation of a specific HmilRNA (aap-milR-11980-x) in honey bee larvae using agomirs and antagomirs.
- Analysis of host gene expression (E75, TTK, AMPs) and larval survival rates.
Main Results:
- 380, 106, 107, and 110 HmilRNAs were identified in A. apis spores and infected larvae at different time points.
- Eighteen conserved HmilRNAs formed a network targeting 188 host genes, including those in Wnt, Hippo, mTOR, MAPK, and Toll/Imd pathways.
- The HmilRNA aap-milR-11980-x was validated to target and repress the honey bee genes E75 and TTK.
- In vivo modulation of aap-milR-11980-x altered E75, TTK, and AMP transcript levels but did not significantly affect larval survival.
Conclusions:
- A. apis HmilRNAs can effectively regulate honey bee larval gene expression through ckRNAi.
- The targeted genes are involved in critical host signaling pathways.
- While molecular pathways are modulated, aap-milR-11980-x may induce sub-lethal physiological changes rather than acute lethality.
- A. apis milRNAs likely fine-tune host responses to facilitate fungal development or resource acquisition.
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