Pesticidal Toxicity of Phosphine and Its Interaction with Other Pest Control Treatments.

Phosphine is the most widely used fumigant for stored grains due to a lack of better alternatives, all of which have serious shortcomings that restrict their use. The extensive use of phosphine has led to the development of resistance among insect pests of grain, which threatens its status as a reliable fumigant. Understanding the mode of action of phosphine as well as its resistance mechanisms provides insight that may lead to improved phosphine efficacy and pest control strategies.

Suppression of a core metabolic enzyme dihydrolipoamide dehydrogenase () protects against amyloid beta toxicity in model of Alzheimer's disease.

A decrease in energy metabolism is associated with Alzheimer's disease (AD), but it is not known whether the observed decrease exacerbates or protects against the disease. The importance of energy metabolism in AD is reinforced by the observation that variants of dihydrolipoamide dehydrogenase (DLD), is genetically linked to late-onset AD. To determine whether DLD is a suitable therapeutic target, we suppressed the gene in that express human Aβ peptide in either muscles or neurons.

Unique genetic variants in dihydrolipoamide dehydrogenase (dld) gene confer strong resistance to phosphine in the rusty grain beetle, Cryptolestes ferrugineus (Stephens).

The rusty grain beetle, Cryptolestes ferrugineus, a major pest of stored commodities, has developed very high levels (>1000×) of resistance to the fumigant phosphine. Resistance in this species is remarkably stronger than reported in any other stored product pests demanding the need to understand the molecular basis of this trait. Previous genetic studies in other grain insect pests identified specific variants in two major genes, rph1 and rph2 in conferring the strong resistance trait.

Hindgut microbiota reflects different digestive strategies in dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae).

Gut microbes play an important role in the biology and evolution of insects. Australian native dung beetles (Scarabaeinae) present an opportunity to study gut microbiota in an evolutionary context as they come from two distinct phylogenetic lineages and some species in each lineage have secondarily adapted to alternative or broader diets. In this study, we characterised the hindgut bacterial communities found in 21 species of dung beetles across two lineages using 16S rRNA sequencing.

Resistance to the Fumigant Phosphine and Its Management in Insect Pests of Stored Products: A Global Perspective.

Development of resistance in major grain insect pest species to the key fumigant phosphine (hydrogen phosphide) across the globe has put the viability and sustainability of phosphine in jeopardy. The resistance problem has been aggravated over the past two decades, due mostly to the lack of suitable alternatives matching the major attributes of phosphine, including its low price, ease of application, proven effectiveness against a broad pest spectrum, compatibility with most storage conditions, and international acceptance as a residue-free treatment. In this review, we critically analyze the published literature in the area of phosphine resistance with special emphasis on the methods available for detection of resistance, the genetic basis of resistance development, key management strategies, and research gaps that need to be addressed.

Attenuation of radiation toxicity by the phosphine resistance factor dihydrolipoamide dehydrogenase (DLD).

Phosphine gas is an excellent fumigant for disinfesting stored grain of insect pests, but heavy reliance on phosphine has led to resistance in grain pests that threatens its efficacy. Phosphine-resistance was previously reported to be mediated by the enzyme DLD. Here we explore the relationship between phosphine toxicity and genotoxic treatments with the goal of understanding how phosphine works.

Modeling Meets Metabolomics-The WormJam Consensus Model as Basis for Metabolic Studies in the Model Organism .

Metabolism is one of the attributes of life and supplies energy and building blocks to organisms. Therefore, understanding metabolism is crucial for the understanding of complex biological phenomena. Despite having been in the focus of research for centuries, our picture of metabolism is still incomplete.

Oxygen and Arsenite Synergize Phosphine Toxicity by Distinct Mechanisms.

Phosphine is the only fumigant approved globally for general use to control insect pests in stored grain. Due to the emergence of resistance among insect pests and the lack of suitable alternative fumigants, we are investigating ways to synergistically enhance phosphine toxicity, by studying the mechanism of action of known synergists, such as oxygen, temperature, and arsenite. Under normoxia, exposure of the model organism Caenorhabditis elegans for 24 h at 20°C to 70 ppm phosphine resulted in 10% mortality, but nearly 100% mortality if the oxygen concentration was increased to 80%.

A high-throughput system used to determine frequency and distribution of phosphine resistance across large geographical regions.

Background: Next-generation sequencing can enable genetic surveys of large numbers of individuals. We developed a genotyping-by-sequencing assay for detecting strong phosphine resistance alleles in the dihydrolipoamide dehydrogenase (dld) gene of Rhyzopertha dominica populations. The assay can estimate the distribution and frequency of resistance variants in thousands of individual insects in a single run.

Potential of Co-Fumigation with Phosphine (PH3) and Sulfuryl Fluoride (SO2F2) for the Management of Strongly Phosphine-Resistant Insect Pests of Stored Grain.

Resistance to phosphine (PH3) in key insect pests of stored grain is increasing, with a requirement for maintaining a dose as high as 1 mg l-1 for 14 d for effective fumigation, which is difficult to achieve under most commercial storage conditions. There is no suitable replacement for PH3, as most of the available alternatives suffer from specific weaknesses, creating an urgent need to increase the efficacy of this fumigant. One such possibility is co-fumigation of PH3 with another fumigant, sulfuryl fluoride (SO2F2-SF), with the goal of decreasing the time required for a successful fumigation.

5-Methoxyindole-2-carboxylic acid (MICA) suppresses Aβ-mediated pathology in C. elegans.

Alzheimer's disease (AD) is an age-related disease characterized by loss of memory and disrupted thinking that is associated with altered energy metabolism. Variants of an important enzyme of energy metabolism, dihydrolipoamide dehydrogenase (dld), have been genetically linked to late-onset AD. Moreover, reduced activity of DLD-containing enzyme complexes is associated with AD progression.

Stress pre-conditioning with temperature, UV and gamma radiation induces tolerance against phosphine toxicity.

Phosphine is the only general use fumigant for the protection of stored grain, though its long-term utility is threatened by the emergence of highly phosphine-resistant pests. Given this precarious situation, it is essential to identify factors, such as stress preconditioning, that interfere with the efficacy of phosphine fumigation. We used Caenorhabditis elegans as a model organism to test the effect of pre-exposure to heat and cold shock, UV and gamma irradiation on phosphine potency.

Variant Linkage Analysis Using Transcriptome Sequencing Identifies a Conserved Phosphine Resistance Gene in Insects.

Next-generation sequencing methods enable identification of the genetic basis of traits in species that have no prior genomic information available. The combination of next-generation sequencing, variant analysis, and linkage is a powerful way of identifying candidate genes for a trait of interest. Here, we used a comparative transcriptomics [RNA sequencing (RNAseq)] and genetic linkage analysis approach to identify the gene.

Metformin Attenuates Aβ Pathology Mediated Through Levamisole Sensitive Nicotinic Acetylcholine Receptors in a C. elegans Model of Alzheimer's Disease.

The metabolic disease, type 2 diabetes mellitus (T2DM), is a major risk factor for Alzheimer's disease (AD). This suggests that drugs such as metformin that are used to treat T2DM may also be therapeutic toward AD and indicates an interaction between AD and energy metabolism. In this study, we have investigated the effects of metformin and another T2DM drug, 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) in C.

Genetic characterization of field-evolved resistance to phosphine in the rusty grain beetle, Cryptolestes ferrugineus (Laemophloeidae: Coleoptera).

Inheritance of resistance to phosphine fumigant was investigated in three field-collected strains of rusty grain beetle, Cryptolestes ferrugineus, Susceptible (S-strain), Weakly Resistant (Weak-R) and Strongly Resistant (Strong-R). The strains were purified for susceptibility, weak resistance and strong resistance to phosphine, respectively, to ensure homozygosity of resistance genotype. Crosses were established between S-strain×Weak-R, S-strain×Strong-R and Weak-R×Strong-R, and the dose mortality responses to phosphine of these strains and their F1, F2 and F1-backcross progeny were obtained.

Genetic Conservation of Phosphine Resistance in the Rice Weevil Sitophilus oryzae (L.).

High levels of resistance to phosphine in the rice weevil Sitophilus oryzae have been detected in Asian countries including China and Vietnam, however there is limited knowledge of the genetic mechanism of resistance in these strains. We find that the genetic basis of strong phosphine resistance is conserved between strains of S. oryzae from China, Vietnam, and Australia.

Inheritance and characterization of strong resistance to phosphine in Sitophilus oryzae (L.).

Sitophilus oryzae (Linnaeus) is a major pest of stored grain across Southeast Asia and is of increasing concern in other regions due to the advent of strong resistance to phosphine, the fumigant used to protect stored grain from pest insects. We investigated the inheritance of genes controlling resistance to phosphine in a strongly resistant S. oryzae strain (NNSO7525) collected in Australia and find that the trait is autosomally inherited and incompletely recessive with a degree of dominance of -0.

Do phosphine resistance genes influence movement and dispersal under starvation?

Phosphine resistance alleles might be expected to negatively affect energy demanding activities such as walking and flying, because of the inverse relationship between phosphine resistance and respiration. We used an activity monitoring system to quantify walking of Rhyzopertha dominica (F.) and a flight chamber to estimate their propensity for flight initiation.

Rapid genome wide mapping of phosphine resistance loci by a simple regional averaging analysis in the red flour beetle, Tribolium castaneum.

Background: Next-generation sequencing technology is an important tool for the rapid, genome-wide identification of genetic variations. However, it is difficult to resolve the 'signal' of variations of interest and the 'noise' of stochastic sequencing and bioinformatic errors in the large datasets that are generated. We report a simple approach to identify regional linkage to a trait that requires only two pools of DNA to be sequenced from progeny of a defined genetic cross (i.

Frogs and estivation: transcriptional insights into metabolism and cell survival in a natural model of extended muscle disuse.

Green-striped burrowing frogs (Cyclorana alboguttata) survive in arid environments by burrowing underground and entering into a deep, prolonged metabolic depression known as estivation. Throughout estivation, C. alboguttata is immobilized within a cast-like cocoon of shed skin and ceases feeding and moving.

Determining changes in the distribution and abundance of a Rhyzopertha dominica phosphine resistance allele in farm grain storages using a DNA marker.

Background: The lesser grain borer, Rhyzopertha dominica (F.), is a highly destructive pest of stored grain that is strongly resistant to the fumigant phosphine (PH3 ). Phosphine resistance is due to genetic variants at the rph2 locus that alter the function of the dihydrolipoamide dehydrogenase (DLD) gene.

A core metabolic enzyme mediates resistance to phosphine gas.

Phosphine is a small redox-active gas that is used to protect global grain reserves, which are threatened by the emergence of phosphine resistance in pest insects. We find that polymorphisms responsible for genetic resistance cluster around the redox-active catalytic disulfide or the dimerization interface of dihydrolipoamide dehydrogenase (DLD) in insects (Rhyzopertha dominica and Tribolium castaneum) and nematodes (Caenorhabditis elegans). DLD is a core metabolic enzyme representing a new class of resistance factor for a redox-active metabolic toxin.

The Redox System in C. elegans, a Phylogenetic Approach.

Oxidative stress is a toxic state caused by an imbalance between the production and elimination of reactive oxygen species (ROS). ROS cause oxidative damage to cellular components such as proteins, lipids, and nucleic acids. While the role of ROS in cellular damage is frequently all that is noted, ROS are also important in redox signalling.

The rph2 gene is responsible for high level resistance to phosphine in independent field strains of Rhyzopertha dominica.

The lesser grain borer Rhyzopertha dominica (F.) is one of the most destructive insect pests of stored grain. This pest has been controlled successfully by fumigation with phosphine for the last several decades, though strong resistance to phosphine in many countries has raised concern about the long term usefulness of this control method.

WormScan: a technique for high-throughput phenotypic analysis of Caenorhabditis elegans.

Background: There are four main phenotypes that are assessed in whole organism studies of Caenorhabditis elegans; mortality, movement, fecundity and size. Procedures have been developed that focus on the digital analysis of some, but not all of these phenotypes and may be limited by expense and limited throughput. We have developed WormScan, an automated image acquisition system that allows quantitative analysis of each of these four phenotypes on standard NGM plates seeded with E.