Insect-resistant cotton

Cotton tolerant to lepidopteran pests through introduction of the vip3A(a) gene which codes for an insecticidal protein that targets lepidopteran insect species. COT102 cotton was developed as an alternative and novel insect control option for lepidopteran pests of cotton. COT102 was also developed to help prevent and manage resistance to Cry proteins due to the different insecticidal mode of action of VIP proteins.  The aph4 gene, coding for hygromycin-B phosphotransferase (APH4) was used as a selectable marker.

Cultivar: Coker 312

pCOT-1

Coding sequence of the Vip3A gene was altered for optimal expression in plant cells.

Information on the inserted DNA sequences (in Spanish):
El gen insertado en el algodón COT102, vip3A(a) confiere resistencia a lepidopteros al codificar la proteina VIP3A, el gen proviene de Bacillus thuringiensis.

Se utilizó el sistema de transformación de A. tumefaciens. Los genes insertados en COT102, junto con los componentes necesarios para su regulación en planta son: Gen vip3A(a) que codifica la proteína VIP3A; Promotor Act2 de Arabidosis thaliana que confiere la expression de gen vip3A(a); nos 3' (terminador del gen principal); gen aph4 de E. coli (Marcador de selección); gen ubi3 de Arabidosis thaliana (promotor del gen marcador); nos 3' (terminador del gen marcador).

Southern blot analysis of the genomic DNA from COT102 revealed the incorporation of single intact copies of the vip3A(a) and aph4 genes, along with intact copies of their respective regulatory sequences. Results of these analyses also demonstrated that none of the vector backbone sequences, including the streptomycin adenyltransferase (aadA) gene, were incorporated into the genomic DNA.

The cotton line COT102 was genetically engineered to resist attack from lepidopteran insect pests such as the cotton bollworm (Helicoverpa zea), tobacco budworm (Heliothis virescens), pink bollworm (Pectinophora gossypiella), fall armyworm (Spodoptera frugiperd), beet armyworm (Spodoptera exigua), soybean looper (Pseudoplusia includens), cabbage looper (Trichoplusia ni), and cotton leaf perforator (Bucculatrix thurberiella).

This insect resistance is conferred by the vip3A(a) gene, originally isolated from the common soil bacterium Bacillus thuringiensis (Bt) strain AB88. The vip3A(a) gene produces the insect control protein VIP3A in the plant tissues. VIP3A is a member of a class of recently discovered insecticidal proteins: VIP (vegetative insecticidal proteins) proteins are expressed by the bacterium during the vegetative stage, as well as during sporulation, the stage at which the delta-endotoxins (i.e., Cry proteins) are expressed.

VIP proteins have an insecticidal mode of action similar to that of the delta-endotoxins: the ingestion by targeted insects leads to feeding cessation, loss of gut peristalsis, insect paralysis, and death. As with Cry proteins, VIP proteins also possess an active proteolytic core, which is activated by insect gut proteases, and binds to specific sites localized on the midgut lining of susceptible insect species. However, the VIP3A protein targets different molecules (i.e., receptors) in the mid-gut lining, and the binding results in the formation of ion channels distinct from those formed by delta endotoxins, such as Cry1Ab.

VIP proteins are not expected to affect other invertebrate and vertebrate organisms, including beneficial arthropods, birds and mammals. Only lepidopteran insect species possess VIP binding sites on the surface of their gut epithelia, therefore, livestock animals and humans are not susceptible to these proteins. Also, since only lepidopteran insect species are targeted by the VIP proteins, species of other insect orders, including beneficial and pest species, are not expected to be affected by this insecticidal protein.