Biology Reference
In-Depth Information
14.1 Overview
Genetic modification of pest and beneficial arthropods can be achieved by mul-
tiple methods. Initially, the only methods available were artificial selection or
hybridization. After it became possible to develop genetically modified
Drosophila
using transposable-element (TE) vectors, scientists focused on transgenesis
(insertion of exogenous genes into the nuclear genome) using TE vectors. That
approach has limitations (possible lack of stability and randomness of the inser-
tion of the transgene), as well as a potential for horizontal transfer (HT). Once
RNA interference (RNAi) was discovered, its possible use to control pests began
to be explored. Paratransgenesis (the insertion of genetically modified symbionts
into an insect) has been studied as a method for control of vector-transmitted dis-
eases. Another genetic modification involves the introduction of novel endosym-
bionts into species previously lacking that symbiont, with the goal of interrupting
the transmission of pathogens such as dengue or malaria by mosquitoes. Homing
endonucleases, TAL effector nucleases (TALENs), and zinc-finger nucleases offer
the promise of specific genome modifications, although this research has not yet
produced modified arthropods for deployment in pest-management programs.
Molecular-genetic methods could improve genetic-control programs, especially
the sterile insect technique, in which males of pest species are mass reared, ster-
ilized by irradiation, and released to mate with wild females, resulting in sup-
pression or eradication of the population over time. Producing sterile males or
producing only females using molecular tools could improve the efficiency and
cost-effectiveness of such programs. Other goals include producing honey bees
(
Apis mellifera
) that are disease resistant, and silk moths (
Bombyx mori
) that pro-
duce improved silk or novel drugs. Natural enemies used in biological control pro-
grams could be modified to enhance their effectiveness by altering their sex ratio,
host range, temperature and relative humidity tolerances, or diapause attributes.
Genetic manipulation of the nuclear genome with recombinant DNA methods
requires methods for efficient and stable insertion of exogenous genes, as well as
the availability of useful genes, appropriate promoters, and other regulatory ele-
ments to obtain effective expression of the inserted gene in both space and time.
The resultant transgenic insects should be contained in the laboratory with effec-
tive procedures until permits have been obtained from appropriate regulatory
authorities that would allow their release into the environment for either short-
term evaluation or permanent release. Potential risk issues to be resolved before
the release of a transgenic arthropod include whether: the inserted gene(s) (or
trait) is stable and the likelihood the modified genes can be transferred horizon-
tally to other populations or species (and the consequences if that did occur).
Another concern is whether the released insects will perform as expected with
