Insect-resistant cotton is divided into transgenic univalent insect-resistant cotton and transgenic bivalent insect-resistant cotton. Transgenic monovalent insect-resistant cotton is a kind of insect-resistant cotton, which transforms a Bt insecticidal protein gene from bacteria that can specifically destroy the digestive tract of Helicoverpa armigera into cotton, so that this insecticidal protein exists in cotton cells, specifically destroying the digestive system of Lepidoptera pests such as Helicoverpa armigera and causing their death, but it is harmless to people and animals.
Its core technology applied for the national invention patent in 1995 and was officially authorized in 1998. 200 1, which was awarded the Gold Award for Invention Patent by the International Intellectual Property Organization and China National Intellectual Property Administration. It marks that China has become the second country in the world to independently develop insect-resistant cotton after the United States.
Insect-resistant cotton is resistant to insects because a parasporal crystal called δ-endotoxin can be synthesized in the cotton plant after the exogenous Bt gene is integrated into the cotton plant. This kind of crystal is protein crystal, which can be hydrolyzed into toxic peptides under the alkaline conditions and the action of enzymes in its intestine, or simply under alkaline conditions, and will be poisoned soon.
The general process of toxic attack is that δ -endotoxin dissolves in the midgut of insects and is interpreted by midgut protease water to release active fragments. The active fragment passes through the peritrophic membrane, combines with the receptor of the brush border membrane of midgut epithelial cells, and further inserts into the membrane to form pores or ion channels. It will lead to ion penetration, and water will enter the midgut cells, leading to cell expansion and rupture.
In addition, the destruction of ion gradient also disturbed the normal transmembrane potential and acid-base balance of midgut, and affected the absorption of nutrients. Make the larvae stop feeding, paralyze and finally die. Because the gastrointestinal tract of human body and most animals is acidic, this kind of protein is nontoxic to human body and most animals.