Engineered symbionts activate honey bee immunity and limit pathogens

Inducing immune bee genes Honey bees are prone to parasitism by theVarroa mite, which is a vector for several bee pathogens. However, honey bees are also host to the symbiotic gut bacteriumSnodgrassella alvi. Leonardet al. engineeredS. 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 reducedVarroa mite survival.Science , this issue p.573 ; see also p.504