Abstract
Honey bee (Apis mellifera) gene expression related to immunity for hymenoptaecin (AmHym) and defensin-1 (AmDef-1), longevity for vitellogenin (AmVit2) and stem cell proliferation for poly U binding factor 68 kDa (AmPuf68) was compared following Varroa destructor parasitism, buffer injection and injection of V. destructor compounds in its homogenate. In adults, V. destructor parasitism decreased expression of all four genes, while buffer injection decreased expression of AmHym, AmPuf68 and AmVit2, and homogenate injection decreased expression of AmPuf68 and AmVit2 but increased expression of AmDef-1 relative to their respective controls. The effect of V. destructor parasitism in adults relative to the controls was not significantly different from buffer injection for AmHym and AmVit2 expression, and it was not significantly different from homogenate injection for AmPuf68 and AmVit2. In brood, V. destructor parasitism, buffer injection and homogenate injection decreased AmVit2 expression, whereas AmHym expression was decreased by V. destructor parasitism but increased by buffer and homogenate injection relative to the controls. The effect of varroa parasitism in brood was not significantly different from buffer or homogenate injection for AmPuf68 and AmVit2. Expression levels of the four genes did not correlate with detectable viral levels in either brood or adults. The results of this study indicate that the relative effects of V. destructor parasitism on honey bee gene expression are also shared with other types of stresses. Therefore, some of the effects of V. destructor on honey bees may be mostly due to wounding and injection of foreign compounds into the hemolymph of the bee during parasitism. Although both brood and adults are naturally parasitized by V. destructor, their gene expression responded differently, probably the result of different mechanisms of host responses during development.
Highlights
Varroa destructor is the most deleterious parasitic mite of the honey bee, Apis mellifera [1]
As previously reported [13, 16,17,18], this study showed that V. destructor parasitism resulted in decreased expression of AmDef-1, AmHym, AmPuf68 and AmVit2 relative to its cage control at one or more time points for both adults and brood, except for AmPuf68 and AmDef-1 in brood
The idea of immunosuppression during varroa parasitism is supported by Kanbar and Engels [9], who showed that V. destructor can maintain open wounds in the honey bee integument and repeatedly feed on the same open wounds over a long period of time, and by Richards et al [29], who showed that saliva of V. destructor can physically damage haemocytes
Summary
Varroa destructor is the most deleterious parasitic mite of the honey bee, Apis mellifera [1]. V. destructor females puncture the cuticle of immature or adult honey bees with their chelicerae, creating an open wound, injecting saliva into the haemolymph and using their hypostome to feed on the honey bee’s haemolymph [9]. Another effect is the vectoring/activation of honey bee viruses, such as deformed wing virus (DWV) and Kashmir bee virus (KBV), which can be transmitted in the saliva of V. destructor through its chelicerae [10, 11]. V. destructor parasitism may suppress expression of numerous honey bee genes. V. destructor suppressed expression of genes in the immune system, like those for the antimicrobial peptides (AMPs), defensin-1 and hymenoptaecin, as well as genes related to longevity and development, like the storage protein, vitellogenin, and the putative cell proliferation regulator, poly U binding factor 68 kDa ( known as Half Pint or pUf68) [12, 13]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
