A SALIVARY CHITINASE OF VARROA DESTRUCTOR INFLUENCES HONEY BEE IMMUNITY AND MITE’S SURVIVAL

Varroa destructor creates a wound in the host’s cuticle through which it feeds on haemolymph and fat body, representing an important stress factor that weakens honeybee colonies and promotes the spreading of diseases. In order to facilitate feeding, this ectoparasitic mite delivers a complex of factors with its salivary secretions. The characterization of these factors is still largely elusive and any progress in this area will offer new insights into the molecular basis of Varroahoneybee interactions, on which to develop new sustainable strategies of mite control. Here, we have used a functional genomics pipeline to identify V. destructor salivary proteins putatively involved in the regulation of host physiology, and their expression in salivary glands has been assessed by qRT-PCR and in situ hybridization. This approach allowed the identification of a salivary chitinase, which was subsequently studied from a functional point of view. In vivo studies were based on gene knockdown followed by artificial infestation of honeybee pupae. The effectiveness and the time course of the silencing were assessed and associated with the observed level of mortality on experimental Varroa mites. To study the effect of the salivary chitinase of V. destructor on honeybee gene expression, we analyzed the transcriptome of worker pupae in response to parasitism by silenced mites. The results obtained indicate an important role of this enzyme in the modulation of host immune response.