behavioral-analysis-locomotor-dysfunction-drosophila-melanogaster-as

Behavioral Analysis of Locomotor Dysfunction in <em>Drosophila melanogaster</em> as a Readout for Neurotoxicity

This protocol presents a high-throughput, cost-effective method for assessing neurotoxicity in the fruit fly (Drosophila melanogaster) by quantifying ...

University of the Azores

Entomopathogenic nematodes are used as biological control agents against a broad range of insect pests. We ascribed the pathogenicity of these organisms to the excretory/secretory products (ESP) released by the infective nematode. Our group characterized different virulence factors produced by  that underlie its success as an insect pathogen. A novel ShK-like peptide (ScK1) from this nematode that presents high sequence similarity with the ShK peptide from a sea anemone was successfully produced recombinantly in . The secondary structure of ScK1 appeared redox-sensitive, exhibiting a far-UV circular dichroism spectrum consistent with an alpha-helical secondary structure. Thermal denaturation of the ScK1 allowed estimating the melting temperature to 59.2 ± 0.1 °C. The results from toxicity assays using  as a model show that injection of this peptide can kill insects in a dose-dependent manner with an LD of 16.9 µM per adult within 24 h. Oral administration of the fusion protein significantly reduced the locomotor activity of insects after 48 h ( < 0.05, Tukey's test). These data show that this nematode expresses insecticidal peptides with potential as next-generation insecticides.

A ShK-like Domain from  with Bioinsecticidal Potential.

The Japanese beetle Popillia japonica is a pest insect that feeds on hundreds of species of wild and cultivated plants including important fruit, vegetable, and field crops. Native to Japan, the pest has invaded large areas of the USA, Canada, the Azores (Portugal), Italy, and Ticino (Switzerland), and it is considered a priority for control in the European Union. We determined the complete mitochondrial genome sequence in 86 individuals covering the entire distribution of the species. Phylogenetic analysis supports a major division between South Japan and Central/North Japan, with invasive samples coming from the latter. The origin of invasive USA samples is incompatible, in terms of the timing of the event, with a single introduction, with multiple Japanese lineages having been introduced and one accounting for most of the population expansion locally. The origin of the two invasive European populations is compatible with two different invasions followed by minimal differentiation locally. Population analyses provide the possibility to estimate the rate of sequence change from the data and to date major invasion events. Demographic analysis identifies a population expansion followed by a period of contraction prior to the invasion. The present study adds a time and demographic dimension to available reconstructions.

The direction, timing and demography of Popillia japonica (Coleoptera) invasion reconstructed using complete mitochondrial genomes.

We report the draft genome sequence of  strain ZMCS4, isolated from . The assembled genome consists of 4.5 Mbp, comprising 25 contigs and 4,128 coding sequences. This genome will provide insights into further studies on relevant CAZymes involved in the hydrolysis of algal cell walls.

Draft genome sequence of  strain ZMCS4, a putative CAZyme-producing bacteria isolated from the marine brown algae .

, commonly known as the Portuguese Man o' War, is one of the most venomous members of the Cnidaria yet is poorly understood. This article investigates the toxicity of  venom by assessing its behavioral and toxicological effects on . The venom administered orally revealed dose- and time-dependent mortality, with an LD50 of 67.4 μg per fly. At sublethal doses, the treated flies displayed uncoordinated movement and fell when attempting to climb. Real-time analysis of flies exposed to the venom revealed hyperexcitability followed by paralysis, with phenotypes similar to those observed in vertebrate models. The venom was shown to be non-thermolabile, as no significant differences in behavior and locomotion were observed between flies exposed to untreated or thermally treated venom. The circadian rhythm alterations, the enhanced light attraction, and the reduction in heat avoidance suggest altered neuronal function. This abnormal behavior indicates that the venom contains bioactive molecules, opening avenues for discovering new compounds with potential for pharmacological applications.

Revealing the Bioactivities of  Venom Using  as a Model.

As entomopathogenic nematodes (EPNs) are used as biological control agents, their survival and persistence are crucial to ensure success in application against insect pests. The survival of Heterorhabditis and Steinernema species is dependent on abiotic and biotic factors in the environment. Abiotic stress environments such as desiccation, temperature, and ultraviolet radiation (UV) severely impact their performance on field. EPNs produce and secrete effector molecules during the early stages of infection to interfere with the molecular mechanisms that control the insect innate immune function. Also, EPN effectors facilitate the subsequent release and spread of their symbiotic bacteria within the host. Hence, a comprehensive understanding of the underlying survival and virulence mechanisms enabling protection against environmental conditions and insect host immune responses is imperative to realistically enhance their performance on field. Thus, identifying key players regulating EPN survival, virulence and immunity could invariably contribute towards developing more robust, reliable solutions and application strategies including genetic tools and formulation technologies.

Entomopathogenic nematodes: Survival, virulence and immunity.

Invasive species are an increasing global threat given their ability to rapidly spread and adapt to novel environments. The adverse ecological and economic impacts of invasive species highlight the critical need to understand the mechanisms that underpin invasion processes and success. The Japanese beetle, Popillia japonica, is an invasive pest of remarkable interest, as it feeds on hundreds of economically valuable plant species. It has been expanding outside of its native range in Japan since the first decades of the 20th century, colonising large areas of North America and, more recently, Europe. Here, we compared whole-genome resequencing data from individuals encompassing the entire species distribution to study the geographic differentiation of P. japonica populations and reconstruct expansion routes from Japan to the USA and Europe. We found six genomically distinguishable clusters, corresponding to the approximate colonisation areas at a continental scale. Our analysis supported an ancestral divergence between South and North/Central Japan, with the latter being the source of the initial invasion to the USA. Coalescent simulations supported independent bridgehead events from the USA to the Azores and Italy. We also investigated possible signals of selection to better understand the adaptive mechanisms that underlie the invasion success of P. japonica. However, the absence of strong selection signatures suggested that the beetle's adaptive ability might be embedded in pre-existing genomic features. Our comprehensive genome-wide dataset allowed a detailed inference of the invasion process and may be useful in determining the origin of P. japonica individuals in future invasion events.

Article	Year
A ShK-like Domain from with Bioinsecticidal Potential. Toxins\| PubMed ID: 36356004	2022
The direction, timing and demography of Popillia japonica (Coleoptera) invasion reconstructed using complete mitochondrial genomes. Scientific reports\| PubMed ID: 38531924	2024
Draft genome sequence of strain ZMCS4, a putative CAZyme-producing bacteria isolated from the marine brown algae . Microbiology resource announcements\| PubMed ID: 38534151	2024
Revealing the Bioactivities of Venom Using as a Model. Toxins\| PubMed ID: 39591246	2024
Entomopathogenic nematodes: Survival, virulence and immunity. Journal of invertebrate pathology\| PubMed ID: 40412605	2025
Whole Genome Resequencing Reveals Origins and Global Invasion Pathways of the Japanese Beetle Popillia japonica. Molecular ecology\| PubMed ID: 40600371	2025

Duarte Toubarro

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