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Biotechnology

Insects, Nematodes, and Biotechnology

Insects and nematodes are the world's most important pests of agricultural plants and livestock. They cause billions of dollars of losses to growers and livestock producers every year because of lowered yields, quality deterioration, and diseases. Pesticides are a major tool for their control. Safer alternatives to control these pests are needed urgently because an ever-escalating number of pesticides cause potential harm to the environment and human health. The advent of biotechnology is leading us to exciting potential strategies to control these pests.

Since 1991, the Entomology and Nematology and the Biologically Based Pest Management programs in the NIFA National Research Initiative (NRI) have supported research aimed toward developing novel control strategies for insect and nematode pests and the genetic improvement of beneficial species such as pollinators and biological control agents. Projects that use the tools of biotechnology have increased dramatically in these programs over the last 15 years. Four general areas of research related to insects, nematodes, and biotechnology and selected examples of funded projects are described below:

Resistance Management to Genetically Modified Crops

Genetic engineers have modified crops to continuously express the toxin, Bacillus thuringiensis (Bt), in these plants. However, insects have the innate ability to develop resistance to genetically modified crops just as quickly as they have in crops bred for insect resistance using traditional breeding methods. Prudent management strategies are needed to minimize the onset of resistance to genetically modified crops. One recent approach has been to apply a noninsecticidal chemical to crop plants. This induces the genes to express the Bt protein to targeted sites on the plant. If Bt is not continuously expressed in the plant, then exposure of insect pests to the Bt toxin will be lessened. In this way it is believed that susceptibility to the Bt toxin will be maintained and development of resistance will be delayed. Other research is aimed at studying the genes that lead to resistance and using molecular maps to localize these genes. A better understanding of how these genes function could lead to better ways to interfere with the development of resistance in the field.

Genetic Improvement of Biological Control Agents and Beneficial Insects

Several promising biological control agents such as entomophagous nematodes or baculoviruses have had limited commercial potential because they can attack one or a few hosts, or they do not persist long enough to provide effective control. Molecular techniques are now available to manipulate the genes that regulate the range of hosts attacked. This approach is an important step in making biological control agents more effective against a wider range of pests. Other examples include manipulation of nematode genes to enhance their ability to resist desiccation from ultra-violet light or to suppress the immune response of their hosts.

In addition, improvement of pollinators such as the European honey bee is being investigated to enhance their resistance to diseases such as American Foul Brood. Other research supported by the NRI includes the development of microarray approaches to study the molecular basis of honey bee responses to pheromones.

Transgenesis of Pests

Pests can be genetically modified to render them sterile or incapable of transmitting diseases to plants or livestock. Genetic techniques are being studied to replace natural pest populations with genetically modified ones. For example, researchers are studying a gene transfer system called Piggy bac for use in vectoring desired traits into insects, such as the oriental fruit fly, Bactrocera dorsalis, or the fall army worm, Spodoptera exigua. Other approaches involve genetically sterilizing insects such as the stored products pest Plodia interpunctella. Sterilization is brought about using gene silencing or RNA interference of genes that are critical for embryonic development.

Development of Designer Pesticides or Vaccines

Molecular approaches are used to design pesticides that disrupt the growth and development of insects. Insect viruses can be manipulated genetically to cause enzymes to be either over-produced or not produced at all. In this way, many researchers are using basic knowledge on insect development to develop new approaches to insect control. In addition, other researchers have discovered and purified an enzyme produced in the saliva of a blood-sucking fly, Haematobia irritans, which has been shown to delay blood clotting in livestock. They have cloned the genetic information (cDNA) encoding this protein and used it to produce large quantities of a recombinant form of this molecule. It is hoped that these studies will lead to the design of an anti-feeding vaccine to protect cattle from this serious pest.

In 2003, NIFA also initiated a funding opportunity titled “Functional Genomics of Agriculturally Important Organisms.” Support is offered for the four major groups of organisms:

  • Insects and mites.
  • Microbes.
  • Plants.
  • Animals.

The goal of this program is to increase the understanding of the biological role of gene sequences in agriculturally important plants, animals, insects, and microbes and to link these sequences to physiological functions or agricultural and food processes. Because the goal of the program is to support large-scale functional analysis of genomic sequences, proposals may include gene expression profiling, proteomics, and/or metabolomics.

 

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