Biology Reference
In-Depth Information
Minos
was discovered in
Drosophila hydei
and can produce stable germ-line
transformation in insects (
Loukeris et al. 1995
,
Catteruccia et al. 2000
), and can
transform human cell lines (
Klinakis et al. 2000
). To reduce potential risk with
genetically modified insects for use in pest-management programs, it may be
necessary to eliminate TE vector sequences after transforming an insect, even
if the element has been “disabled.” See the discussion below on “conversion,”
which indicates that, under some circumstances, even disabled TE vectors can
become active.
The
piggyBac
element was isolated from a nucleopolyhedrosis virus infecting
cell cultures of the moth
Trichoplusia ni
(
Fraser 2000
), and it has a broad host
range. Today, it is the most-used vector for genetic modification of the nuclear
genome of insects.
14.5.2 Paratransgenesis (Genetic Modification of Symbionts)
The genetic modification of symbionts of insects is called
paratransgenesis
(
Miller
et al. 1987
,
Aksoy et al. 2008, Coutinho-Abreu et al. 2010
).
Coutinho-Abreu et al.
(2010)
evaluated the status and challenges of paratransgenesis, with the goals of
reducing insect vectorial capacity or to eliminate disease-causing agents.
Beard
et al. (1992, 1993, 2000)
demonstrated that genetic engineering of insect gut sym-
bionts is feasible by transforming a bacterial symbiont of
Rhodnius prolixus
, the
Chagas-disease vector. The extracellular symbiont lives in the gut lumen and is
transmitted from adult to progeny by contamination of eggshells or of food with
infected feces. The modified symbionts had ampicillin and thiostrepton resistance
genes, as well as genes coding for cecropin A and related pore-forming molecules
(
Richards 1993, Beard et al. 2000
). The antibiotic resistance genes provided a selec-
tive advantage to the transgenic symbionts so they could survive antibiotics in the
blood meal. The cecropin A and related molecules make holes in cell membranes,
perhaps leading to lysis of the Chagas disease-causing agent.
Field trials were conducted in Guatemala to determine whether the engi-
neered symbiont of
Rhodnius
could be transmitted to
Rhodnius
by a simulated
triatomine-fecal material called CRUZIGARD (Hurwitz 2011a,b).
Hurwitz et al.
(2011b)
acknowledged, “deployment of genetically altered lines of bacteria to
target field populations of triatomine bugs may have profound environmental
consequences.” To assess the possible risk of horizontal gene transfer, a model
was developed that attempted to simulate the environmental conditions of such
a project (
Matthews et al. 2011
).
Durvasula et al. (2008)
also transformed a bacte-
rial symbiont of
Triatoma infestans
, another vector of the Chagas disease-causing
agent in South America, with a single-chain antibody.
