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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

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Inducing immune bee genes

Honey bees are prone to parasitism by the Varroa mite, which is a vector for several bee pathogens. However, honey bees are also host to the symbiotic gut bacterium Snodgrassella alvi. Leonard et al. engineered S. alvi to produce double-stranded RNA (dsRNA)—a stimulus for insect RNA interference defense responses—from a plasmid containing two inverted promoters tagged with a fluorescent label (see the Perspective by Paxton). This dsRNA module can be targeted to interfere with specific bee genes as well as crucial viral and mite genes. The authors found that gene expression could be blocked for at least 15 days as the symbionts established in the bees' guts and continuously expressed the dsRNA constructs. S. alvi with specifically targeted plasmids not only suppressed infection with deformed wing virus but also effectively reduced Varroa mite survival.

Science, this issue p. 573; see also p. 504

Abstract

Honey bees are essential pollinators threatened by colony losses linked to the spread of parasites and pathogens. Here, we report a new approach for manipulating bee gene expression and protecting bee health. We engineered a symbiotic bee gut bacterium, Snodgrassella alvi, to induce eukaryotic RNA interference (RNAi) immune responses. We show that engineered S. alvi can stably recolonize bees and produce double-stranded RNA to activate RNAi and repress host gene expression, thereby altering bee physiology, behavior, and growth. We used this approach to improve bee survival after a viral challenge, and we show that engineered S. alvi can kill parasitic Varroa mites by triggering the mite RNAi response. This symbiont-mediated RNAi approach is a tool for studying bee functional genomics and potentially for safeguarding bee health.

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