A proctolin-like peptide is regulated after baculovirus infection and mediates in caterpillar locomotion and digestion.

Baculoviruses constitute a large group of invertebrate DNA viruses, predominantly infecting larvae of the insect order Lepidoptera. During a baculovirus infection, the virus spreads throughout the insect body producing a systemic infection in multiple larval tissues, included the central nervous system (CNS). As a main component of the CNS, neuropeptides are small protein-like molecules functioning as neurohormones, neurotransmitters, or neuromodulators. These peptides are involved in regulating animal physiology and behavior and could be altered after baculovirus infection. In this study, we have investigated the effect of Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) infection on expression of Spodoptera exigua neuropeptides and neuropeptide-like genes. Expression of the gene encoding a polypeptide that resembles the well-known insect neuropeptide proctolin and named as proctolin-like peptide (PLP), was downregulated in the larval brain following infection and was chosen for further analysis. A recombinant Autographa californica multiple nucleopolyhedrovirus (AcMNPV) overexpressing the C-terminal part of the PLP was generated and used in bioassays using S. exigua larvae to study its influence on the viral infection and insect behavior. AcMNPV-PLP-infected larvae showed less locomotion activity and a reduction in growth compared to larvae infected with wild type AcMNPV or mock-infected larvae. These results are indicative of this new peptide as a neuromodulator that regulates visceral and skeletal muscle contractions and offers a novel effector involved in the behavioral changes during baculovirus infection.

Identification of new viral variants specific to the honey bee mite Varroa destructor.

Large-scale colony losses among managed Western honey bees have become a serious threat to the beekeeping industry in the last decade. Multiple factors contribute to these losses, but the impact of Varroa destructor parasitism is by far the most important, along with the contribution of some pathogenic viruses vectored by the mite. So far, more than 20 viruses have been identified infecting the honey bee, most of them RNA viruses. They may be maintained either as covert infections or causing severe symptomatic infections, compromising the viability of the colony. In silico analysis of available transcriptomic data obtained from mites collected in the USA and Europe, as well as additional investigation with new samples collected locally, allowed the description of three RNA viruses, two of them variants of the previously described VDV-2 and VDV-3 and the other a new species reported here for the first time. Our results showed that these viruses were widespread among samples and that they were present in the mites as well as in the bees but with differences in the relative abundance and prevalence. However, we have obtained strong evidence showing that these three viruses were able to replicate in the mite, but not in the bee, suggesting that they are selectively infecting the mite. This opens the door to future applications that may help controlling the mite through biological control approaches.