Biology Reference
In-Depth Information
9.13 Other TEs Can Transform
D. melanogaster
Several types of TEs have been used to transform
D. melanogaster
, includ-
ing
piggyBac
(
Lobo et al. 1999
),
hobo
(
Ladeveze et al. 1998
),
mariner
(
Garza
et al. 1991
), and
Minos
(
Loukeris et al. 1995
). The
hobo
element occurs natu-
rally in populations of
D. melanogaster
, so it is not surprising that it can serve as
a transformation vector.
Minos
was discovered in a related species,
D. hydei
. A
TE vector derived from
mariner
, found originally in
D. mauritiana
, also is effec-
tive in transforming
D. melanogaster
(
Garza et al. 1991
).
piggyBac
, isolated from
a nuclear polyhedrosis virus infecting a
Trichoplusia ni
cell line (Lepidoptera),
is able to transpose in
D. melanogaster
. The finding of
piggyBac
within a virus
suggests one mechanism by which TEs could move horizontally between insects.
piggyBac
is related to class II short-inverted-repeat elements, which includes
hobo
,
Minos
,
Hermes
,
mariner
,
P
,
Tc1
(found in nematodes), and
Ac
(found in
plants).
9.14 Improved Transformation Tools for
Drosophila
The efficiency of TE-mediated germ-line transformation is dependent both upon
the efficiency of the vector and the ability to detect (select) the transformed
progeny.
Benedict et al. (1994)
reported that a parathion hydrolase gene (
opd
),
isolated from bacteria, under the control of a
Drosophila hsp70
promoter, con-
ferred resistance to paraoxon in
D. melanogaster
and suggested that this gene
could serve as a semidominant selectable marker to detect transformation.
Benedict et al. (1994, 1995)
also suggested the
opd
gene could be inserted into
beneficial arthropods (parasitoids and predators) for improved pest manage-
ment. The resistant natural enemies could survive the treatment with organo-
phosphate insecticides, whereas the target pests could not. However, due
to their long residual activity and high toxicity to mammals, the Food Quality
Protection Act has eliminated the use of organophosphates in the United States.
The potential horizontal transfer of pesticide-resistance genes to pest species
could be detrimental, so this selectable marker should be used only for labora-
tory studies and should be eliminated before any releases into the environment.
The use of the green fluorescent protein (GFP) as a selectable marker in trans-
formed
D. melanogaster
and other insects has improved detection (
Brand 1995,
Yeh et al. 1995, Plautz et al. 1996, Tsien 1998, Hazelrigg 2000, Pinkerton et al.
2000
).
Horn et al. (2000)
reported that eye-specific expression of GFP outper-
forms the mini-
white
marker in
Drosophila
germ-line transformation experi-
ments. A red fluorescent protein is also useful as a marker for identifying
transgenic insects (
Horn et al. 2002
).
