Most of the Bt cotton varieties express Bt genes in all whole-plant tissues.
Scientists from Ankata University in Turkey and partners developed a
triple-gene construct for the confined expression of GNA, cry1Ac, and cp4
epsps genes to targeted insect biting sites instead of whole-plant tissues.
They cloned it at downstream of a wound-inducible promoter isolated from
Asparagus officinalis (AoPR1). Furthermore, to widen the range of
resistance, GNA was driven by the 35S promoter to target the sap-sucking
insects such as aphids which impose large losses in cotton production. To
select the transformants in selection medium and for glyphosate tolerance,
cp4 epsps gene was included with GNA and cry1Ac genes.
Results showed that the introduction of cry1Ac and GNA to cotton plant
conferred resistance to Spodoptera littoralis (African cotton leafworm) and
Aphis gossypii Glover (cotton aphid). The results indicate that the
restriction of cry1Ac protein to insect biting sites along with a plant
lectin attributes significantly contribute to insect pest management