Engineered symbionts activate honey bee immunity and limit pathogens

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Science  31 Jan 2020:
Vol. 367, Issue 6477, pp. 573-576
DOI: 10.1126/science.aax9039
  • Fig. 1 Engineered S. alvi colonizes and functions in bee guts.

    (A) Colonization of newly emerged honey bees by different inoculum sizes. The percentage of bees colonized in each treatment is annotated above the inoculation dose. N = 53 bees from two hives. (B) Stability of S. alvi colonization over time. N = 48 bees from three hives. Colors in (A) and (B) correspond to different source hives. (C) Stability of GFP expression by engineered S. alvi over time. (D) Photograph of dissected bee. S. alvi resides in the ileum (gray box). (E and F) Ilea of bees 11 days after colonization with nonfluorescent (E) or fluorescent (F) S. alvi. E2-Crimson fluorescence from engineered S. alvi is blue. Scale bars, 150 μm. Error bars in (A) to (C) are 95% bootstrap confidence intervals.

  • Fig. 2 Symbiont-mediated RNAi reduces expression of a specific host gene and alters feeding behavior and physiology.

    (A) Plasmid design for off-target dsRNA control plasmid (pDS-GFP) and InR1 knockdown plasmid (pDS-InR1). (B) Bees colonized with engineered S. alvi expressing InR1 dsRNA (pDS-InR1 plasmid) show reduced expression of InR1 throughout body regions for 10 days compared to bees colonized with off-target dsRNA control (pDS-GFP). Total N = 29 bees from one hive. (C) pDS-InR1 plasmid increases host feeding activity (sucrose sensitivity response), measured 5 days after inoculation. Curves are a binomial family generalized linear model fit to the response data for N = 67 bees from two hives. (D) pDS-InR1 plasmid significantly increases bee weight, measured 10 and 15 days postinoculation (Mann-Whitney U test). Total N = 135 bees from one hive. See fig. S4 for data from an additional trial. Error bars and shading represent SEs. **P < 0.01; ***P < 0.001.

  • Fig. 3 Symbiont-produced RNAi can improve honey bee survival after viral injection.

    (A) Design of the DWV knockdown construct pDS-DWV2. (B) Survival curves of bees monitored for 10 days after injection with DWV or the phosphate-buffered saline (PBS) control. Bees inoculated with pNR, pDS-GFP, or pDS-DWV2 and then injected with PBS showed no significant change in survival (dotted lines). When injected with DWV, bees inoculated with pDS-DWV2 showed increased survival compared with bees inoculated with pNR (no dsRNA control) or pDS-GFP (off-target dsRNA control). ***P < 0.001 (Wald test); NS, not significant. Total N = 980 bees, sourced from three separate hives.

  • Fig. 4 Symbiont-produced RNAi kills Varroa mites feeding on honey bees.

    (A) Design of pDS-VAR plasmid targeting essential Varroa genes. (B) Survival curves for Varroa mites that fed on bees colonized with engineered S. alvi. Total N = 253 mites. All mites came from a single infested hive. Bees were sourced from three separate hives. **P < 0.01 (Wald test); NS, not significant.

Supplementary Materials

  • Engineered symbionts activate honey bee immunity and limit pathogens

    Sean P. Leonard, J. Elijah Powell, Jiri Perutka, Peng Geng, Luke C. Heckmann, Richard D. Horak, Bryan W. Davies, Andrew D. Ellington, Jeffrey E. Barrick, Nancy A. Moran

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods 
    • Figs. S1 to S11
    • Tables S1 to S4 
    • References 

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