Abstract
Bacillus thuringiensis (Bt) bacterium is found in various ecological habitats, and has natural entomo-pesticidal properties, due to the production of crystalline and soluble proteins during different growth phases. In addition to Cry and Cyt proteins, this bacterium also produces Vegetative insecticidal protein (Vip) during its vegetative growth phase, which is considered an excellent toxic candidate because of the difference in sequence homology and receptor sites from Cry proteins. Vip proteins are referred as second-generation insecticidal proteins, which can be used either alone or in complementarity with Cry proteins for the management of various detrimental pests. Among these Vip proteins, Vip1 and Vip2 act as binary toxins and have toxicity toward pests belonging to Hemiptera and Coleoptera orders, whereas the most important Vip3 proteins have insecticidal activity against Lepidopteran pests. These Vip3 proteins are similar to Cry proteins in terms of toxicity potential against susceptible insects. They are reported to be toxic toward pests, which can’t be controlled with Cry proteins. The Vip3 proteins have been successfully pyramided along with Cry proteins in transgenic rice, corn, and cotton to combat resistant pest populations. This review provides detailed information about the history and importance of Vip proteins, their types, structure, newly identified specific receptors, and action mechanism of this specific class of proteins. Various studies conducted on Vip proteins all over the world and the current status have been discussed. This review will give insights into the significance of Vip proteins as alternative promising candidate toxic proteins from Bt for the management of pests in most sustainable manner.
Highlights
Bacillus thuringiensis (Bt) is an aerobic, gram-positive, entomopathogenic bacterium
Many researchers demonstrated that Bt strains secreted Vip (Vegetative insecticidal protein) proteins during the vegetative growth phase and these proteins do not share any structural and sequence homology with Cry proteins, these are considered as a tremendous complement or supplement source of Cry toxins in resistance management and crop protection
This study suggested that with increased concentration of Vip3Aa, the concentration of degraded lysosomes is increased, which causes the build-up of autophagosomes
Summary
Bacillus thuringiensis (Bt) is an aerobic, gram-positive, entomopathogenic bacterium. Bacillus thuringiensis-based biopesticides have become a vital part of insect pest management strategies This bacterium has successfully been utilized as a source of cry genes for plant genetic engineering to develop transgenic crops showing resistance toward various detrimental insect pests (Tohidfar and Salehi Jouzani, 2008; Tohidfar et al, 2013; Melo et al, 2016; Tabashnik and Carrière, 2017). In addition to Cry and Cyt toxins, Bt strains can produce other insecticidal proteins during the vegetative growth phase. Many researchers demonstrated that Bt strains secreted Vip (Vegetative insecticidal protein) proteins during the vegetative growth phase and these proteins do not share any structural and sequence homology with Cry proteins, these are considered as a tremendous complement or supplement source of Cry toxins in resistance management and crop protection. Total number in database Gene Length Signal peptide (aa) Protoxin Protein size (kDa) Active Protein size (kDa) Amino Acids (aa) Domain
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