Unveiling the insecticidal gene profile of novel antifungal Bacillus thuringiensis strain NBAIR BtAr
摘要
Bacillus thuringiensis is known for its insecticidal properties and antagonistic activity against phytopathogens. One such potent indigenous strain, NBAIR BtAr, which has shown antifungal properties against Sclerotium rolfsii, has not been explored for its insecticidal potential. Hence entomopathogenic potential of NBAIR BtAr against Spodoptera frugiperda was analyzed by in-vitro bioassay, and genes regulating its biocontrol potential were identified by in-silico analysis. In-vitro bioassay of NBAIR BtAr using the spore-crystal mixture against second instar larvae of S. frugiperda showed 92% mortality at 96 h with an LC50 value of 42.92 µg/mL. In-silico analysis of NBAIR BtAr genome confirmed the presence of two novel Cry proteins with 51.39% and 39.57% amino acid sequence identity to Cry14Aa1 and Cry21Aa2, respectively, and a known pesticidal protein, Spp1Aa1, with 79.48% identity. Genes viz. inhA1, inhA2, bmp1, enhancin, and chitinase C enhancing the insecticidal potential of NBAIR BtAr were also identified. The identified insecticidal genes were validated through PCR by designing specific primers. Structural analysis of these pesticidal proteins was conducted using Phyre2 software with pseudo multiple sequence alignments, which showed 74, 79, and 88% coverage for Cry14Aa1, Cry21Aa2, and Spp1Aa1, respectively. Additionally, the three-dimensional structures of these proteins were modelled with 100% confidence, which showed 21 and 28% identity to Cry1Ac (Cry14Aa1 and Cry21Aa2) and 73% identity to perfringolysin O (Spp1Aa). The present study revealed that B. thuringiensis strain NBAIR BtAr can be used for the effective management of S. frugiperda and also identified the novel genes responsible for the bioefficacy of the strain.