In the past centuries, viruses have benefited from globalization to spread across the globe, infecting new host species and populations. A growing number of viruses have been documented in the western honey bee, Apis mellifera. Several of these contribute significantly to honey bee colony losses. This review synthetizes the knowledge of the diversity and distribution of honey-bee-infecting viruses, including recent data from high-throughput sequencing (HTS). After presenting the diversity of viruses and their corresponding symptoms, we surveyed the scientific literature for the prevalence of these pathogens across the globe. The geographical distribution shows that the most prevalent viruses (deformed wing virus, sacbrood virus, black queen cell virus and acute paralysis complex) are also the most widely distributed. We discuss the ecological drivers that influence the distribution of these pathogens in worldwide honey bee populations. Besides the natural transmission routes and the resulting temporal dynamics, global trade contributes to their dissemination. As recent evidence shows that these viruses are often multihost pathogens, their spread is a risk for both the beekeeping industry and the pollination services provided by managed and wild pollinators.

Aquaporins (AQPs) or water channels render the lipid bilayer of cell membranes permeable to water. The numerous AQP subtypes present in any given species, the transport properties of each subtype and the variety of methods of their regulation allows different cell types to be transiently or permanently permeable to water or other solutes that AQPs are capable of transporting (e.g. urea or glycerol). AQPs have been well characterized in all vertebrate classes, other than reptilia. Here we review the current state of knowledge of invertebrate AQPs set in the context of the much more thoroughly studied vertebrate AQPs. By phylogenetic analysis of the total AQP complement of several completed insect genomes, we propose a classification system of insect AQPs including three sub-families (DRIP, BIB and PRIP) that have one representative from all the complete insect genomes. The physiological role of AQPs in invertebrates (insects, ticks and nematodes) is discussed, including their function in common invertebrate phenomena such as high-volume liquid diets, cryoprotection and anhydrobiosis.

Environmental and agricultural pollination services by honey bees, Apis mellifera, and honey production are compromised by high levels of annual colony losses globally. The majority are associated with disease caused by deformed wing virus (DWV), a positive-strand RNA virus, exacerbated by the ectoparasitic mite Varroa destructor. To improve honey bee health, a better understanding of virus transmission and pathogenesis is needed which requires the development of tools to study virus replication, transmission, and localisation. We report the use of reverse genetic (RG) systems for the predominant genetically distinct variants of DWV to address these questions. All RG-recovered viruses replicate within 24 h post-inoculation of pupae and could recapitulate the characteristic symptoms of DWV disease upon eclosion. Larvae were significantly less susceptible but could be infected orally and subsequently developed disease. Using genetically tagged RG DWV and an in vitro Varroa feeding system, we demonstrate virus replication in the mite by accumulation of tagged negative-strand viral replication intermediates. We additionally apply a modified DWV genome expressing a fluorescent reporter protein for direct in vivo observation of virus distribution in injected pupae or fed larvae. Using this, we demonstrate extensive sites of virus replication in a range of pupal tissues and organs and in the nascent wing buds in larvae fed high levels of virus, indicative of a direct association between virus replication and pathogenesis. These studies provide insights into virus replication kinetics, tropism, transmission, and pathogenesis, and produce new tools to help develop the understanding needed to control DWV-mediated colony losses.

In addition to a constitutive water channel activity, several studies suggest Aquaporin-1 (AQP1) functions as a nonselective monovalent cation channel activated by intracellular cGMP, although variability in responsiveness between preparations has led to controversy in the field. Data here support the hypothesis that responsiveness of the AQP1 ionic conductance to cGMP is governed by tyrosine phosphorylation. Wild-type and mutant human AQP1 channels expressed in Xenopus laevis oocytes were characterized by two-electrode voltage clamp and optical osmotic swelling analyses. Quadruple mutation by site-directed mutagenesis of barrier hydrophobic residues (Val50, Leu54, Leu170, Leu174) to alanines in the central pore induced inward rectification of the ionic current and shifted reversal potential by approximately ϩ10 mV, indicating increased permeability of tetraethylammonium ion. Introduction of cysteine at lysine 51 in the central pore (K51C) in a cysteineless template created new sensitivity to block of the conductance by mercuric ion. Mutations of candidate consensus sites and pharmacological manipulation of serine and threonine phosphorylation did not alter cGMP-dependent responses; however, mutation of tyrosine Y253C or pharmacological dephosphorylation prevented ion channel activation. Modification of Y253C by covalent addition of a negatively charged group [2-sulfonatoethyl methanethiosulfonate sodium salt (MTSES)] rescued the cGMP-activated conductance response, an effect reversed by dithiothreitol. Results support the proposal that phosphorylation of tyrosine Tyr253 in the carboxyl terminal domain, confirmed by Western blot, acts as a master switch regulating responsiveness of AQP1 ion channels to cGMP, and the tetrameric central pore is the ion permeation pathway. These findings advance resolution of a standing controversy and expand our understanding of AQP1 as a multifunctional regulated channel.

Aquaporin-1 (AQP1) is a major intrinsic protein that facilitates flux of water and other small solutes across cell membranes. In addition to its function as a water channel in maintaining fluid homeostasis, AQP1 also acts as a nonselective cation channel gated by cGMP, a property shown previously to facilitate rapid cell migration in a AQP1-expressing colon cancer cell line. Here we report two new modulators of AQP1 channels, bacopaside I and bacopaside II, isolated from the medicinal plant Bacopa monnieri Screening was conducted in the Xenopus oocyte expression system, using quantitative swelling and two-electrode voltage clamp techniques. Results showed bacopaside I blocked both the water (IC50 117 μM) and ion channel activities of AQP1 but did not alter AQP4 activity, whereas bacopaside II selectively blocked the AQP1 water channel (IC50 18 μM) without impairing the ionic conductance. These results fit with predictions from in silico molecular modeling. Both bacopasides were tested in migration assays using HT29 and SW480 colon cancer cell lines, with high and low levels of AQP1 expression, respectively. Bacopaside I (IC50 48 μM) and bacopaside II (IC50 14 μM) impaired migration of HT29 cells but had minimal effect on SW480 cell migration. Our results are the first to identify differential AQP1 modulators isolated from a medicinal plant. Bacopasides could serve as novel lead compounds for pharmaceutic development of selective aquaporin modulators.