1a. Objectives (from AD-416):
The goal of this project is to develop innovative and sustainable technologies to manage insect pests and their natural enemies to reduce damage to trees, shrubs, and flowering perennial plants in managed and unmanaged urban landscapes. Lepidopteran and coleopteran pests are the principal defoliators in urban landscapes and nearby forests, and constitute 60% of recorded invasive insect species in North America. The research focuses on five of the most destructive lepidopteran and coleopteran pests in urban landscapes: gypsy moth, winter moth, and dogwood borer; and emerald ash borer and Asiatic garden beetle; however, research results are expected to be broadly applicable to other urban landscape insect pests. The research is organized around three objectives: (1) identify and synthesize plant-derived semiochemicals and insect pheromones attractive to pests, and design insect monitoring and management strategies employing them; (2) develop microbial and arthropod natural enemies as biocontrol agents of native and exotic pests of landscape plants; and (3) identify at the molecular level genes and gene pathways critical for success of landscape pests; employ molecular technologies to determine the role of host pathways targeted by entomopathogens; and target these pathways with natural or molecular biopesticides to kill pests.
1b. Approach (from AD-416):
This highly interdisciplinary project combines concepts and methodologies from analytical and synthetic organic chemistry, insect chemical behavior, insect pest-pathogen genomics, and microbial and insect ecology to develop strategies to combat urban landscape pests. Plant-derived semiochemicals and insect pheromones will be identified, and novel chemical and biological syntheses will be devised to enable their use for monitoring pest populations, disrupting pest reproduction, and luring pests into traps to be exposed to pathogenic microorganisms. Ecological attributes of pathogens underlying virulence, specificity, and accessibility to hosts will be determined. Transcriptome analysis of gypsy moth larvae challenged with various classes of pathogens will expose insect molecular vulnerabilities exploited by virulent pathogens. Naturally occurring pathogens best able to exploit these vulnerabilities will be applied directly to the environment, or placed in traps with species-specific semiochemicals to lure pests into contact with the pathogens to initiate epizootics. Experimental native and exotic assemblages of woody and herbaceous urban landscape plants will be characterized according to the natural enemy resources that they provide, and tested for their ability to support natural enemies and thereby to promote effective biocontrol of urban landscape pests.
3. Progress Report:
Significant progress was made in achieving three objectives towards our overall goal. To address our goal to “Identify and synthesize plant-derived semiochemicals and insect pheromones attractive to pests” effective long-distance volatile attractants were made by several strategies for an emerald ash borer (EAB) monitoring trapping system. EAB invasive pest threatens native ash species. We developed an in vitro system to produce a plant volatile that stimulates EAB antennae. To produce an active enzyme, we constructed recombinant baculoviruses for expression in insect cells, and cloned a fruit fly gene for another enzyme that synthesizes a precursor line that produced the attractant in insect cells. We also synthesized 7ES directly from commercially available starting material. To address our goal to “Develop microbial and arthropod natural enemies as biocontrol agents of insect pests of landscape plants” we characterized baculovirus (NPV) isolates in the IIBBL virus collection at molecular and genome sequence levels for use against gypsy moth (GM), the most serious U.S. landscape pest. Isolates from Korea, Japan, Russia, Spain, and Massachusetts were selected for characterization by complete genome sequencing. A complete draft of the Massachusetts genome and partial drafts of genomes for other isolates were produced. To develop an alternative to winter moth larvae for evaluating NPVs for WM control, we initiated a cell line from WM embryos from dissected and homogenized eggs. We also identified a diverse group of non-crystal-forming Bacilli from forest soil that carried insecticidal toxin genes like those in Photorhabdus and Yersinia, but distinct from other bacteria. Multi-locus sequence typing analysis of B. thuringiensis populations (Bts) revealed great diversity even among close phylogenetic relatives. The majority of Bts belonged to few major phylogenetic groups. The distribution of crystal-forming Bacillus species from hardwood forests revealed a new group of mild pathogens related to B. weihenstephanensis which grow at low temperature. Sampling at different elevations revealed that these were dominant crystal-forming Bacilli on slopes and hilltops, but absent from floodplains. Floodplain soils were dominated by Bacilli belonging to an undescribed group producing trapezoidal crystals, which were occasionally toxic to GM. To address our goal to “Identify genes and gene pathways critical for success of pests; employ molecular technologies to determine the role of host pathways targeted by entomopathogens; and target these pathways to kill pests” we conducted studies and analyzed transcriptome profiles to identify expressed genes in GM cell line Ld652Y and healthy 3rd instar larvae for both midgut and hemocyte tissues. Tissues were separately infected with Bt and other microbial pathogens, and parasitized by braconid parasitoid G. flavicoxis. Transcriptome profiles were generated for each to assess differences in levels of gene transcription between healthy and pathogen-infected tissues and to identify target genetic pathways. This will allow us to determine molecular vulnerabilities of GM to pathogens and parasitoids.
1. Gypsy moth (cell line IPBL-Ld652Y) total expressed gene profile determined. Almost no genetic information existed for gypsy moth (GM) even though this information could help scientists devise new biological control strategies. GM cells were analyzed to determine the total genetic components (called the “transcriptome”) produced by the cells. More than 14,000 transcripts were identified for GM. Numerous virus genetic components associated with the GM cells were also discovered, as well as several candidate genetic components of interest for developing into biological control methods.
Dupuy, C., Gundersen, D.E., Cusson, M. 2012. Genomics and Replication of Polydnaviruses. In: Beckage, N.E., Drezen, J.M., editors. Parasitoid Viruses: Symbionts and Pathogens. London, England: Elsevier. p. 47-61.