Figure 2.

Hypothetical pathways and models of honey bee responses to Varroa-parasitism (A) and the bee tolerant genotype (B). Arrows and dashes indicate positive and negative regulation, respectively. Gene names in bold are up-regulated. In A) one of the consequences of the Varroa parasitism is a decline in immune capacity which induces the proliferation in bees of the Deformed Wing Virus (DWV). The boost of DWV multiplication might cause cellular and molecular damage, inducing the production of protein repair (Pcmt) and the labelling of proteins for degradation (Nedd8). In addition, regulated genes that might be affected by the presence of the DWV are indicated. Mites might decrease the production of dopamine (ple) and inhibit genes known for indirectly preventing neural degeneration in aged adults, which could explain the cognitive impairment often observed in adults parasitized by Varroa. In B) different genes can be associated to behavioral tolerance to Varroa. Tolerant and non-tolerant bees differ significantly by the expression of genes involved in the nervous system development. The olfactory pathway and neurons excitability seem also to play an important role in Varroa-tolerance. See text for a full discussion on the genes involved in the pathways presented.