Biology Reference
In-Depth Information
9.15.5 hobo
The
hobo
vector transposed in a plasmid-based excision assay in several dro-
sophilid species (
Handler and Gomez 1995
), and in cells of
Trichoplusia ni
and
Helicoverpa zea
(
DeVault et al. 1996
), as well as in several tephritids, including
Anastrepha suspensa
,
Bactrocera dorsalis
,
Bactrocera cucurbitae
,
Ceratitis capi-
tata
, and
Toxotrypana curvicauda
(
Handler and Gomez 1996
). Elements related
to
hobo
were found in many of the tephritids.
hobo
mediated germ-line trans-
formation of
D. virilis
(
Lozovskaya et al. 1996
).
Excision of
hobo
from
H. zea
was stimulated by heat shocks that presumably
stimulated the production of an endogenous
hobo
-like transposase. The exci-
sion rate was 8- to 10-fold higher than that seen for the normal host or other
dipteran species (
Atkinson et al. 1993
) and, in hindsight, could have been pre-
dicted because
hobo
had been found previously in
H. zea
(
DeVault and Narang
1994
). The instability indicates the importance of checking the target insect spe-
cies' genome to be sure that endogenous elements related to the TE vector are
lacking.
9.16 Cross Mobilization of TE Vectors
Laboratory assays were conducted to compare the ability of
Minos
,
piggyBac
,
mariner
, and
Hermes
vectors to
cross mobilize
each other (
Sundararajan et al.
1999
). The
hobo
transposase functioned equally well with
hobo
and
Hermes
substrates. Conversely, the
Hermes
transposase rarely was able to excise the
hobo
elements from plasmids.
The hAT family of elements (which includes TEs from widely divergent host
taxa, including plants, fungi, fish, insects, and humans) appears able to function
in novel hosts, and to move horizontally relatively easily (
Kidwell and Lisch 1997,
Kempken and Windhofer 2001
). These attributes make them desirable as vec-
tors for inserting transgenes into arthropods but could be considered negative
attributes from the point of view of risk assessments if transgenic insects that
contain them are being evaluated for release into the environment (
Hoy 2000
).
The ability of different TEs to mobilize endemic (native) TEs (cross mobilization)
is not limited to
Hermes
and
hobo
(
Sundararajan et al. 1999
).
9.17 Conversion of Inactive TE Vectors to Activity
The ability of disabled TE vectors to function in transgenic arthropods should
be evaluated before transgenic arthropods are released into the environment
(
Hoy 2000
) because an inactivated
P
vector was converted to activity in a process
called
conversion
(
Peronnet et al. 2000
). The defective
P
vector was converted
