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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