Análise in silico de genes de toxinas inseticidas em cepas de Bacillus thuringiensis

Abstract

Currently, pesticides use in agricultural production is extensive and meets the growing demand for food production. However, the excessive use of pesticides in crops has caused serious ecological damage, leaving residues in the environment, in addition to being extremely harmful to human health. Additionally, chemical pesticides affect non-target insects, which in turn can lead to the loss of populations beneficial to agriculture. An alternative to reduce pesticide applications is the use of biological control, using microorganisms such as Bacillus thuringiensis. These bacteria stand out for presenting entomopathogenic activity against various insect pests orders. Due to the numerous possible applications of B. thuringiensis toxins, the need to characterize strains of this species is justified. Thus, the present study aimed to identify and characterize, by in silico methods, proteins with potential insecticidal activity in four B. thuringiensis strains that have not yet been characterized in the literature. An alignment, using BLASTp, was performed against reference sequences of already known toxins, obtaining sequences with significant alignments from the proteome of each strain. Then, the 31 sequences obtained were submitted to the BPPRC database alignment tool, obtaining sequence identity percentage with other known toxins. In addition, physicochemical properties such as molecular weight, isoelectric point and sequence size were calculated by the Expasy platform for comparative purposes. CD-Search and InterProScan were used to obtain and analyze the conserved domains and SWISS-MODEL for the simulation of the three-dimensional proteins models. Among the 31 sequences obtained, 9 presented 100% identity with proteins from the BPPRC bank (Cry1Ab18, Cry1Ja2, Cry1Bb1, Cry1Id1, Cry2Ad, Cry3Aa12, Cry7Da1, Cry7Fb1 and Cry1Ab1). Among the 22 proteins without identity, 5 were classified as Cry, 5 as Vpb1, 4 as Vpa2, 3 as Mpp and one as Vip3. Furthermore, 4 of the 22 proteins did not fit the parameters of B. thuringiensis insecticidal toxins. The results showed a large variation in the quantity and types of insecticidal genes among the analyzed strains.