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Larvae of the greater wax moth (Galleria mellonella) possess the remarkable ability to consume and rapidly degrade low-density polyethylene. Previous studies have investigated the involvement of the animal's microbiome, but little is known about the host's actual role and if it benefits from biodegradation of this synthetic polymer. We used a combination of RNA sequencing and biochemical approaches to assess caterpillars fed honeycomb, fed polyethylene (PE), or starved for up to 72 h. Sequencing of gut transcripts revealed PE-fed larvae retain an expression profile consistent with normal intestinal function but also show distinct molecular signatures indicative of enhanced fatty acid metabolism (FAM). Further, quantification of total lipid content validated the impact of a PE diet on FAM; in contrast to lipid-depleted starved animals, PE-fed caterpillars maintain lipid reserves similar to honeycomb-fed larvae. Additionally, we found the activity of putative enzymes involved in lipid oxidation (e.g., alcohol dehydrogenase) are considerably higher in PE-fed larvae, indicating that on a functional level, these caterpillars are inducing pathways to effectively metabolize PE. Overall, we put forward a hypothesized model where the similarity in chemical structure between PE and its natural honeycomb diet has endowed larvae of G. mellonella with the extraordinary capability to derive energy from PE as an exclusive food source through pre-existing metabolic pathways.

Soybean (Glycine max) has become an important crop in Manitoba, Canada, with a 10-fold increase in dedicated acreage over the past decade. Given the rapid increase in production, scarce information about foliar diseases present in the province has been recorded. In order to describe the foliar pathogens affecting this legume, we harnessed next-generation sequencing (NGS) to carry out a comprehensive survey across Manitoba in 2016. Fields were sampled during the V2/3 (33 fields) and R6 (70 fields) growth stages, with at least three symptomatic leaves per field collected and subjected to RNA sequencing. We successfully detected several bacteria, fungi, and viruses known to infect soybean, including Pseudomonas savastanoi pv. glycinea, Septoria glycines, and Peronospora manshurica, as well as pathogens not previously identified in the province (e.g., Pseudomonas syringae pv. tabaci, Cercospora sojina, and Bean yellow mosaic virus). For some microorganisms, we were able to disentangle the different pathovars present and/or assemble their genome sequence. Since NGS generates data on the entire flora and fauna occupying a leaf sample, we also identified residual pathogens (i.e., pathogens of crops other than soybean) and multiple species of arthropod pests. Finally, the sequence information produced by NGS allowed for the development of polymerase chain reaction-based diagnostics for some of the most widespread and important pathogens. Although there are many benefits of using NGS for large-scale plant pathogen diagnoses, we also discuss some of the limitations of this technology.

For more than 50 years DEET (N,N-Diethyl-m-toluamide) has been considered the gold standard of repellents. It is applied to the skin or clothing to deter mosquitoes and other blood-sucking invertebrate pests from approaching and/or settling, and ultimately it provides temporary protection from bites. Despite rampant global use, surprisingly little is understood about DEET’s mode of action and the molecular targets of the active ingredient. Furthermore, the theories into its mechanism for repellency are largely based off fruit fly and mosquito research. Since ticks possess a unique sensory structure, the Haller’s organ, the specific genes and pathways associated with DEET avoidance may differ from insects. In these studies, we collected American dog ticks (Dermacentor variabilis) from four natural populations within Manitoba, Canada. We first carried out behavior assays, which showed DEET effectively repelled the ticks. RNA sequencing revealed that DEET caused a rapid and substantial reduction in the abundance of transcripts encoding cytochrome P450 and acetylcholinesterase genes, which gradually recovered over the 24 h time course. Finally, enzymatic kinetics provided functional support for DEET’s role as an effective inhibitor of P450 s. While many facets of its mode of action remain to be worked out, our study provides valuable insights into the molecular underpinnings of DEET’s repellence in ticks.

Worldwide crop losses due to plant diseases exceed $60 billion annually. Next to fungi, viruses represent the greatest contributor to those losses, and these are transmitted in nature primarily by insects. Mexican bean beetles (Epilachna varivestis) are formidable pests of soybean, as well as efficient vectors of several soybean-infecting viruses, including Bean pod mottle virus (BPMV). Beetle-borne viruses have a unique mode of transmission, though their interactions with host plants and vectors remain poorly understood. In these studies, we implemented targeted metabolite profiling and high throughput RNA sequencing approaches to explore metabolic and molecular changes in soybean leaves infected with BPMV. The virus-infected plants showed altered defence signaling and amino acid concentrations—and most strikingly—had dramatically higher sucrose levels. Based on the results, we performed a series of E. varivestis behavioral bioassays using near-isogenic soybean lines of differing foliar sucrose levels in an attempt to more directly associate sucrose content and E. varivestis feeding preferences. Choice assays revealed E. varivestis is more attracted to BPMV-infected soybean than to healthy plants. Moreover, no-choice assays indicated that beetles consume less foliage per plant but ultimately feed on more plants in a given time period if they are higher in sucrose. Importantly, these virus-driven changes to beetle feeding preferences are likely to increase BPMV spread in natural environments.

For nearly 400 million years, insects and plants have been embattled in an evolutionary arms race. Insects have developed diverse feeding strategies and behaviors in an effort to circumvent and overcome an extensive collection of plant defense tactics. Sap-sucking insects often inject saliva into hosts plants, which contains a suite of effector proteins and even microbial communities that can alter the plant's defenses. Lacking salivary glands, leaf-feeding beetles represent an interesting group of phytophagous insects. Feeding beetles regurgitate onto leaf surfaces and it is thought that these oral secretions influence insect-plant interactions and even play a role in virus-vector specificity. Since the molecular and biological makeup of the regurgitant is virtually unknown, we carried out RNA sequencing and 16S rDNA analysis on a major soybean pest, Epilachna varivestis, to generate the first ever beetle "regurgitome" and characterize its microbiome. Interestingly, the regurgitant is comprised of a rich molecular assortment of genes encoding putative extracellular proteins involved in digestion, molting, immune defense, and detoxification. By carrying out plant inoculation assays, we reinforced the fundamental role of the regurgitant in beetle-borne virus specificity. Ultimately, these studies begin to characterize the importance of regurgitant in virus transmission and beetle-plant interactions.

We present the first complete genome sequence of the tombusvirus Tobacco necrosis virus D (TNV-D) from North America, obtained from an infected soybean plant. Compared with the three other TNV-D genomes isolated from different geographic regions and host plants, its nucleotide identities were between 83% and 93%.