Vip3 Safety

Environmental safety of the VIP3

The proteins of Vip3 are original from the bacteria Bacillus thuringiensis. Vip proteins have pesticide properties against some plagues from the family of the lepidopteron. This document seeks to make a collection of information and data relevant to the overall assessment of the environmental hazard of the protein Vip3Ca3 when it is produced in geneticallymodified organisms as E.Coli and the GM corn plant.

Bacillus thuringiensis is a soil bacterium although is found throughout the environment. The protein pesticides produced by B. thuringiensis show a great variety with regard to the mode of action, the specificity of the objective and the mechanism of expression. Pesticide proteins expressed by the strains of B. thuringiensis include antifungalcompounds, δ-exotoxinas,3 and δ-endotoxins, which include the protein Cry and Cyt, that are not structurally related but come from the same bacterium. The Cry proteins are so named because it is stored as parasporals crystals during the formation of the spore, unlike the new protein that was produced by B. thuringiensis during their vegetative phase of growth, in addition to during the stage ofsporulation, so that was called vegetative insecticidal protein (Vip). In addition, while the Cry proteins are isolated as crystals, the Vip proteins are secreted by bacteria and can be isolated directly from the culture medium.
It has been determined that, in reality, there are several variants of Vip which are classified into three classes according to the similarity of the aminoacid sequence:Vip1, Vip2 and Vip3. Of these, the group whose insecticidal properties are more efficient is the Vip3.

The members of the Vip3 family characterized to date exhibit activity against lepidopterans, and several of them do not compete with Cry proteins for binding sites. They are classified into two subfamilies (Vip3A and Vip3B), and some are especially toxic for species with little susceptibility toseveral Cry proteins. All of these features have made Vips a research target for broadening the host-range of B. thuringiensis-based biopesticides and for the management of insect resistance to B. thuringiensis proteins.

Relation between Vip3A and Vip3C

The taxonomic group of proteins that Vip is currently used in the production of GM crop plants resistant to insects is Vip3Aa. Vip3Aa1 mayvary in size from 62 to 66 kDa among different Vip3 proteins and is occasionally known as the “trypsin-resistant core”.

Also, Vip3C proteins maintained only one of the three residues of the C terminus stabilizing domain described for Vip3Aa1 (5). This higher divergence toward the C terminus might indicate lower functional constraints and, consequently, more permissibility to nonsynonymoussubstitutions.

For a preliminary screening of the insecticidal properties of Vip3Ca (host range and toxicity), Vip3Ca3 was picked because of its high yields, expressed in Escherichia coli, column purified, quantified by densitometry, and used to challenge larvae of 10 different lepidopteran species. Bioassays were conducted with neonate larvae that were placed over a surface-contaminated artificial diet.It has been given considerable attention to the possible impacts of the proteins of B. thuringiensis in the Monarch Butterfly (Danaus plexippus), which is not a lepidopter pest in North America. Studies have shown that the proteins Vip3Aa are not toxic to this species of butterfly. However, the differences between the Vip3A and the Vip3C are such that is not possible to determine exactly thetoxicity of the pesticide for the butterfly without making proves.

Preliminary bioassays of larvae from 10 different lepidopteron species indicated that Vip3Ca3 caused more than 70% mortality in four species after 10 days at 4 g/cm2. How the few changes in the Vip3Ca proteolytic processing sites may modify either the protein activity or the host range is uncertain, but different Vip3 proteins...