Steven Whyard

• PhD
• Professor at University of Manitoba

RNA interference (RNAi) is a naturally occurring gene silencing mechanism conserved across organisms with a clearly defined cell nucleus (eukaryotes). Gene silencing by RNAi through the degradation of a target messenger RNA (mRNA) has historically been used as a research tool to study the function of genes. Over the past two decades, silencing of v...

The causative agent of white mold, Sclerotinia sclerotiorum, is capable of infecting over 600 plant species and is responsible for significant crop losses across the globe. Control is currently dependent on broad-spectrum chemical agents that can negatively impact the agroecological environment, presenting a need to develop alternative control meas...

The causative agent of white mold, Sclerotinia sclerotiorum , is capable of infecting over 600 plant species and is responsible for significant crop losses across the globe. Control is currently dependent on broad-spectrum chemical agents that can negatively impact the agroecological environment, presenting a need to develop alternative control mea...

Sclerotinia sclerotiorum is a pathogenic fungus that infects hundreds of crop species, causing extensive yield loss every year. Chemical fungicides are used to control this phytopathogen, but with concerns about increasing resistance and impacts on non-target species, there is a need to develop alternative control measures. In the present study, we...

White mold is caused by the fungal pathogen Sclerotinia sclerotiorum and causes rapid and significant loss in plant yield. Among its many brassicaceous hosts, including Brassica napus (canola) and Arabidopsis, the response of individual tissue layers directly at the site of infection has yet to be explored. Using laser microdissection coupled with...

Sclerotinia sclerotiorum is a pathogenic fungus that infects hundreds of crop species, causing extensive yield loss every year. Chemical fungicides are used to control this phytopathogen, but with concerns about increasing resistance and impacts on non-target species, there is a need to develop alternative control measures. In the present study, we...

Successful integrated management of the invasive predatory sea lamprey (Petromyzon marinus) in the Laurentian Great Lakes of North America is owed largely to the long history of beneficial use of two lampricides: 3-trifluoromethyl-4-nitrophenol (TFM) and 2′,5-dichloro-4′-nitrosalicylanilide (niclosamide). Ensuring continued successful sea lamprey c...

White mold in Brassica napus (canola) is caused by the fungal pathogen Sclerotinia sclerotiorum and is responsible for significant losses in crop yield across the globe. With advances in high-throughput transcriptomics, our understanding of the B. napus defense response to S. sclerotiorum is becoming clearer; however, the response of individual tis...

Efforts to develop more environmentally friendly alternatives to traditional broad-spectrum pesticides in agriculture have recently turned to RNA interference (RNAi) technology. With the built-in, sequence-specific knockdown of gene targets following delivery of double-stranded RNA (dsRNA), RNAi offers the promise of controlling pests and pathogens...

RNA interference (RNAi) has become a widely used technique of knocking down a gene's expression in insects, but its efficacy in some species is limited by a reduced ability of the cells to take in and disperse the double-stranded RNA (dsRNA) throughout the cytoplasm. While RNA transport proteins such as SID-1 and its orthologues can facilitate dsRN...

RNA interference (RNAi) technologies have recently been developed to control a growing number of agronomically significant fungal phytopathogens, including the white mold pathogen, Sclerotinia sclerotiorum. Exposure of this fungus to exogenous double-stranded RNA (dsRNA) results in potent RNAi-mediated knockdown of target genes’ transcripts, but it...

RNA interference (RNAi) techniques are being developed for a range of pest insect control technologies, including the sterile insect technique (SIT) and double-stranded RNA (dsRNA)-based insecticides. In SIT applications, where >99% of the released males should be sterile to meet industry standards, the efficiency of RNAi will need to be improved f...

Exploiting the RNA interference (RNAi) gene mechanism to silence essential genes in pest insects, leading to toxic effects, has surfaced as a promising new control strategy in the past decade. While the first commercial RNAi-based products are currently coming to market, the application against a wide range of insect species is still hindered by a...

Insects face diverse biotic and abiotic stresses that can affect their survival. Many of these stressors impact cellular metabolism, often resulting in increased accumulation of reactive oxygen species (ROS). Consequently, insects will respond to these stressors by increasing antioxidant activity and increased production of heat shock proteins (HSP...

Biliary atresia (BA) is a rare neonatal disease with unknown causes. Approximately 10% of BA cases develop in utero with other congenital defects that span a large spectrum of disease variations, including degeneration of the gall bladder and bile duct as well as malformation of the liver, intestines, and kidneys. Similar developmental alterations...

RNA interference (RNAi) in insects is routinely used to ascertain gene function, but also has potential as a technology to control pest species. For some insects, such as beetles, ingestion of small quantities of double-stranded RNA (dsRNA) is able to knock down a targeted gene's expression. However, in other species, ingestion of dsRNA can be inef...

Daphnia spp. cycle between asexual and sexual reproduction depending on environmental conditions. Under favorable conditions, female offspring are produced, resulting in rapid population expansion; in less favorable conditions, males are produced, initiating the sexual portion of their lifestyle. Although mediated by environmental cues, sex determi...

In the pursuit of better pest- and vector-control strategies, attention returns to an old proven technology, the sterile insect technique (SIT) and related insect population-suppression methods. A major obstacle for any of these approaches that involves the release of sterile males is the separation of males from females during the mass rearing sta...

Canola (Brassica napus) is a commercially-important oilseed in many countries, and flea beetles are considered one of the most damaging pests of this crop plant. The crucifer flea beetle, Phyllotreta cruciferae (Goeze) and the striped flea beetle, Phyllotreta striolata (F.) are the most economically-important pests of canola in North America, and b...

The Queensland fruit fly, Bactrocera tryoni, is Australia’s most important horticultural pest. The Sterile Insect Technique (SIT) has been used to control this species for decades, using radiation to sterilize males before field-release. This method of sterilization can potentially reduce the insects’ abilities to compete for mates. In this study,...

Current agricultural output is challenged by considerable losses in crop yield and post-harvest storage due to fungal infection. Traditional chemical fungicides used to treat these fungi can be ineffective and harmful to the environment if not used properly. With fungicide resistance increasing in fungal pathogens, new environmentally friendly and...

Sclerotinia sclerotiorum, the causal agent of white stem rot, is responsible for significant losses in crop yields around the globe. While our understanding of S. sclerotiorum infection is becoming clearer, genetic control of the pathogen has been elusive and effective control of pathogen colonization using traditional broad-spectrum agro-chemical...

RNA interference (RNAi) is a double-stranded RNA (dsRNA)-mediated method of silencing a gene’s expression, and is often used to study gene functions in model and non-model organisms. When many invertebrates are fed dsRNA, the dsRNA can enter the gut cells and can then spread throughout the organism to induce systemic RNAi. DsRNA transporters such a...

Mosquitoes are considered among the deadliest animals on Earth due to the diseases they carry, such as malaria, yellow fever, dengue fever, and Zika. The Sterile Insect Technique (SIT) is a pesticide-free method of controling pest insects through the production and release of sterile males. For SIT to be used in mosquito control, some difficulties...

Transposable elements (TEs) have been recognized as potentially powerful drivers of genomic evolutionary change, but factors affecting their mobility and regulation remain poorly understood. Chaperones such as Hsp90 buffer environmental perturbations by regulating protein conformation, but are also part of the PIWI-interacting RNA pathway, which re...

Estimated direct and indirect losses of grains and grain-based products caused by stored-product insects range from about 10% in temperate regions to almost 50% in humid tropical areas. Pest management strategies in bulk grains include the use of fumigants such as phosphine and sulfuryl fluoride, and grain protectants, which are sprayed directly on...

Introduction: Canola, which is one of Canada’s most important crops, is prone to attack from a variety of insect pests, with flea beetles (Coleoptera: Chrysomelidae: Galerucinae: Alticini) being the most economically damaging. Synthetic insecticides are routinely used to control the pest insects, but with growing concerns about the negative impacts...

Control of sea lamprey Petromyzon marinus in the Great Lakes requires accurate assessment of the instream distribution of this pest species and the ability to distinguish it from the four lamprey species that are native to the Great Lakes (American brook lamprey Lethenteron appendix, chestnut lamprey Ichthyomyzon castaneus, northern brook lamprey I...

Mosquito-borne diseases threaten over half the world's human population, making the need for environmentally-safe mosquito population control tools critical. The sterile insect technique (SIT) is a biological control method that can reduce pest insect populations by releasing a large number of sterile males to compete with wild males for female mat...

Background: Biliary atresia (BA) is a human infant disease with inflammatory fibrous obstructions in the bile ducts and is the most common cause for pediatric liver transplantation. In contrast, the sea lamprey undergoes developmental BA with transient cholestasis and fibrosis during metamorphosis, but emerges as a fecund adult. Therefore, sea lam...

Lampreys, one of the two surviving groups of ancient vertebrates, have become important models for study in diverse fields of biology. Lampreys (of which there are approximately 40 species) are being studied, for example, (a) to control pest sea lamprey in the North American Great Lakes and to restore declining populations of native species elsewhe...

Approaches based on organismal DNA found in the environment (eDNA) have become increasingly utilized for ecological studies and biodiversity inventories as an alternative to traditional field survey methods. Such DNA-based techniques have been largely used to establish the presence of free-living organisms, but have much potential for detecting and...

Insects cost the agricultural sector billions of dollars every year in lost crop yields and insecticide expenditures. The continued use of chemical insecticides has inadvertently selected for more resistant pest strains, prompting higher doses and more frequent applications to control them. The advent of transgenic plants, such as those expressing...

Lampreys diverged from the jawed vertebrate lineage approximately 500million years ago. Lampreys undergo sex differentiation much later than most other vertebrates, and ovarian differentiation occurs several years before testicular differentiation. The genetic basis of lamprey sex differentiation is of particular interest both because of the phylog...

Environmental DNA (eDNA) is the DNA of an organism that persists in the environment via sources such as mucus, feces, sloughed off cells, and decomposing remains. This DNA can be collected and the species of origin identified. We have developed eDNA assays that detect and distinguish the invasive Sea Lamprey Petromyzon marinus from the four native...

The parasitic sea lamprey (Petromyzon marinus) has caused extensive losses to commercial fish stocks of the upper Great Lakes of North America. Methods of controlling the sea lamprey include trapping, barriers to prevent migration, and use of a chemical lampricide (3-trifluoromethyl-4-nitrophenol) to kill the filter-feeding larvae. Concerns about t...

Abstract RNA interference has already proven itself to be a highly versatile molecular biology tool for understanding gene function in a limited number of insect species, but its widespread use in other species will be dependent on the development of easier methods of double-stranded RNA (dsRNA) delivery. This study demonstrates that RNA interferen...

Deformed wing virus (DWV) is a serious pathogen of the honey bee, Apis mellifera L., vectored by the parasitic mite Varroa destructor. The virus is associated with wing deformity in symptomatic bees, and premature death and reduced colony performance in asymptomatic bees. In the present study we reduced DWV infection by feeding both first instar la...

Carbon dioxide (CO(2)) is an important long-range chemosensory cue used by blood-feeding female mosquitoes to find their hosts. The CO(2) receptor in Drosophila melanogaster was previously determined to be a heterodimer comprised of two gustatory receptor (Gr) proteins, DmGr21a and DmGr63a. In the mosquito Aedes aegypti, two putative orthologous ge...

A serious shortcoming of many insecticides is that they can kill non-target species. To address this issue, we harnessed the sequence specificity of RNA interference (RNAi) to design orally-delivered double-stranded (ds) RNAs that selectively killed target species. Fruit flies (Drosophila melanogaster), flour beetles (Tribolium castaneum), pea aphi...

Proposals to farm non-native and genetically modified species are often highly contentious because there is no reliable method of ensuring that they do not escape, reproduce and become environmental problems. Suggested approaches to prevent breeding outside hatcheries are unable to guarantee sterility in both sexes or cannot easily be applied to an...

The discovery that small RNA molecules act through RNA interference (RNAi) pathways as potent regulators of chromatin structure, messenger RNA (mRNA) abundance and translation, has revolutionized our understanding of gene regulation. These small RNA silencing systems have also been harnessed as powerful tools to manipulate gene expression that can...

With twelve Drosophila genomes now sequenced, there is a growing need to develop higher-throughput methods for identifying the functions of the many newly identified genes. Genetic transformation and RNA interference are two technologies that have been used extensively to facilitate gene-function studies in Drosophila melanogaster, to introduce gen...

Aquaculture animals that escape from farms have the potential to create major environmental problems. These include establishment of potentially destructive feral populations (e.g., Pacific oysters [Crassostrea gigas] in Australia, Atlantic salmon [Salmo salar] in British Columbia) and genetic contamination of wild stocks. The latter includes intro...

We describe here two new transposable elements, CemaT4 and CemaT5, that were identified within the sequenced genome of Caenorhabditis elegans using homology based searches. Five variants of CemaT4 were found, all non-autonomous and sharing 26 bp inverted terminal repeats (ITRs) and segments (152-367 bp) of sequence with similarity to the CemaT1 tra...

The maT clade of transposons is a group of transposable elements intermediate in sequence and predicted protein structure to mariner and Tc transposons, with a distribution thus far limited to a few invertebrate species. We present evidence, based on searches of publicly available databases, that the nematode Caenorhabditis briggsae has several maT...

The maT clade of transposons is a group of transposable elements intermediate in sequence and predicted protein structure to mariner and Tc transposons, with a distribution thus far limited to a few invertebrate species. In the nematode Caenorhabditis elegans, there are eight copies of CemaT1 that are predicted to encode a functional transposase, w...

Bactrocera tryoni is a serious pest of horticulture in eastern Australia. Here we review molecular data relevant to pest status and development of a transformation system for this species. The development of transformation vectors for non-drosophilid insects has opened the door to the possibility of improving the sterile insect technique (SIT), by...

A group of transposons, named maT, with characteristics intermediate between mariner and Tc1 transposons, is described. Two defective genomic copies of MdmaT from the housefly Musca domestica, with 85% identity, were found flanking and imbedded in the MdalphaE7 esterase gene involved in organophosphate insecticide resistance. Two cDNA clones, with...

We examined the relative efficiency of microinjection, electroporation and particle bombardment for introducing DNA into the embryos of the Kuruma prawn, Penaeus japonicus. The amount of DNA that could be delivered into one- to four-celled embryos and subsequently recovered was examined using plasmids with selectable antibiotic resistance. Microinj...

Members of the hAT transposable element family are mobile in non-host insect species and have been used as transformation vectors in some of these species. We report that the Queensland fruit fly, Bactrocera tryoni, contains at least two types of insect hAT elements called Homer and a Homer-like element (HLE). The Homer element is 3789 bp in size a...

Transgenic insect technology will provide opportunities to explore the basic biology of a broad range of insect species in ways that will prove insightful and important. It is also a technology that will provide opportunities to manipulate the genotypes of insects of practical significance to the health and welfare of humans. The Hermes transposabl...

The enzyme triosephosphate isomerase (TPI) was purified to homogeneity from the mosquito Culex tarsalis. Anti-C. tarsalis TPI antibodies cross-reacted with TPIs from other organisms but bands on western blots were most intense with proteins from closely related Dipterans. Using a degenerate primer corresponding to the amino-terminal sequence of the...

Resistance to the organophosphate insecticide, malathion, in a strain of Culex tarsalis mosquitoes is due to increased activity of a malathion carboxylesterase (MCE). To determine whether resistance was due to a qualitative or quantitative change in the MCE, the enzyme was purified from both malathion-resistant and -susceptible mosquitoes. Enzyme k...

Resistance to malathion in a strain of the Australian sheep blowfly is due to a 10-fold increase in malathion carboxylesterase (MCE) activity relative to a more susceptible strain. MCE was purified to apparent homogeneity from these two strains and was shown to be a monomer of 60,500, with a pI of 5.5 in both strains. Purified MCE from both populat...

Malathion resistance in a strain of Culex tarsalis mosquitoes is due primarily to the activity of a malathion carboxylesterase (MCE). The resistant strain was 150 times more resistant to malathion than the susceptible strain and was weakly resistant to malaoxon and carbaryl, but not to any other insecticide tested. The phenotype could be reversed w...

Resistance to the organophosphorus insecticide malathion in genetically related strains of the Australian sheep blowflyLucilia curprina was examined. Separate lines of blowflies were established by homozygosis of the fourth chromosome of the parental RM strain. Both the RM and the derived resistant (der-R) strains are approximately 100 times more r...

The origin and function of introns in eukaryotic genes has provoked considerable debate since their discovery in 1977. Central to this issue are studies on the highly conserved enzyme, triosephosphate isomerase (TPI, EC 5.3.1.1). The 'introns early' argument suggests that introns are as old as the genes themselves and that the apparent correlation...

The role of esterases in malathion resistance in Culex tarsalis has been investigated. When larvae of a resistant and a sensitive strain were placed in water containing [14C]malathion, malathion penetrated to give initially similar internal levels. With resistant mosquitoes, after 15 min the internal malathion concentration decreased to low levels...

Locusta migratoria adults reared at 27–30°C die after 2 h at 50°C, but they survive this temperature stress if first exposed to 45°C for 0.5 to 4.5 h. Fat bodies from adult females produce a set of at least six specific polypeptides with molecular weights of 81, 73, 68, 42, 28, and 24×103 in reponse to heat shock (39–47°C for 1.5 h). These molecula...