Contents - Faperta

Genetic Engineering of Entomopathogenic Microbes for Pest Management 259
Wigle et al., 1990) and hymenopteran insects (Piek et al., 1989; Piek, 1990) can be used for
increasing the effectiveness of baculoviruses. There is a distinct possibility of expressing
excitatory and depressant proteins, as well as Bt toxins, in baculoviruses. Such an expression
would increase the effectiveness of the NPVs, and can also be exploited to broaden
their host range. Signal consequences of all the genes expressed in baculoviruses are processed
appropriately, producing toxin proteins with amino acid terminal sequences similar
to those of native proteins (Luckow and Summers, 1988), but the ratio of expression
varies, depending on the protein being expressed and the signal sequence.
Baculoviruses with Neurotoxins
One of the major focuses for genetic modifi cation has been to increase their effectiveness
through insertion of neurotoxin genes from arthropods, which act by blocking the synaptic
transmission or by inhibiting the activity of ion channels. Because of their specifi city,
natural toxins have become quite useful in designing new biopesticides, including baculoviruses
(Zlotkin et al., 1971a, 1971b, 1971c; Zlotkin, 1988). Genes that code for scorpion,
Androctonus australis Hector (AaIT), and mite venom have been engineered into the
baculovirus (AcNPV) from Autographa californica (Speyer) to increase the effectiveness of
this virus (Tomalski and Miller, 1991; Stewart et al., 1991; Bonning and Hammock, 1996)
(Table 8.2). The AaIT shows remarkable specifi city to insects and has no apparent effects on
mammals (Zlotkin et al., 1971a; Fontecilla-Camps, 1989; DeDianous, Hoarau, and Rochat,
1987). The toxin proteins bind to the sodium channel proteins and affect the neuronal
membranes (Lester et al., 1982; Catterall, 1984; Zlotkin and Gordon, 1985; Zlotkin, 1988).
TABLE 8.2
Genetically Modifi ed Baculoviruses for Pest Management
Insect Species/NPV Gene GMO/Promoter References
Autographa californica NPV
(Ac-NPV)
Androctonus australis
toxin gene (AaIT )
Ac-AaIT Stewart et al. (1991), Hoover
et al. (1995)
Ac-MNPV AaIT Ac–AaIT/ P10 McCutchen et al. (1991)
Bombyx mori NPV (Bm-NPV) AaIT Bm-AaIT Maeda et al. (1991)
Ac-NPV AaIT VAc-LdPD Du and Thiem (1997)
Ac-NPV Enhancin gene from
Trichoplusia ni (AcENh26 )
AcENh26 Hayakawa et al. (2000)
Heliothis zea NPV (Hz-NPV) AaIT Hz-AaIT Treacy, Rensner, and All (2000)
Helicoverpa armigera NPV
(Ha-SNPV)
Egt HaSNPV-egt Sun et al. (2004)
Ac-MNPV Mu-Aga-IV—Agelenopsis
aperta
AsII—Anemonia sulcata
Sh1—Stydactyla
Phsp70 promoter Prikhod ko et al. (1998)
Baculovirus Pyemotes tritici, Tox34 VEV-Tox34 Tomalski and Miller (1991)
Ac-MNPV Juvenile esterase from
Heliothis virescens
p10 promotor Hammock et al. (1990)
Baculovirus Diuretic hormone — Maeda (1989)
Ac-MNPV Viral gene (egt), which
codes for UDP-glycosyl
transferase
— O’Reilly and Miller (1991)