Insecticidal Activity and Histopathological Effects of Vip3Aa Protein from Bacillus thuringiensis on Spodoptera litura

Abstract

Vegetative insecticidal proteins (Vips) are insecticidal proteins synthesized by during the vegetative stage of growth. In this study, Vip3Aa protein, obtained by in vitro expression of the gene from WB5, displayed high insecticidal activity against aside from and. Bioassay results showed that the toxicity of Vip3Aa protein against larvae statistically decreased along with the increase of the age of the larvae, with LC = 2.609 ng/cm for neonatal larvae, LC = 28.778 ng/cm for first instar larvae, LC = 70.460 ng/cm for second instar larvae, and LC = 200.627 ng/cm for third instar larvae. The accumulative mortality of 100% larvae appeared at 72 h for all instars of larvae, when feeding respectively with 83.22, 213.04, 341.40, and 613.20 ng/cm of Vip3Aa toxin to the neonatal and first to third instar larvae. The histopathological effects of Vip3Aa toxin on the midgut epithelial cells of larvae was also investigated. The TEM observations showed wide damage of the epithelial cell in the midgut of larvae fed with Vip3Aa toxin.

Biological activities of the vegetative insecticidal protein Vip3Aa against beet armyworm (Spodoptera exigua)

“…The larvicidal activities of Vip3Aa protoxin and activated toxins were examined in the beet armyworm, S. exigua, and their LC 50 and LC 95 are summarized in Table 1. The results showed that the toxicity of the Vip3Aa35 against the insect larvae used in this experiment was similar to the other Vip3Aa toxins, Vip3Aa16 and Vip3Aa58 [12][13][14]. The amino acid sequence identity and similarity of the Vip3Aa35 compared with the Vip3Aa16 [12] and the Vip3Aa58 [13,14] were 98.8% and 99.1%, respectively.…”

“…The first generation Bt toxins (Cry and Cyt) could form pores in the insect midgut leading to cell disruption [11]; but the mode of action of Vip3 is still unclear. The toxicities of Vip3Aa16 [12] and Vip3Aa58 [13] were reported against Spodoptera frugiperda, S. exigua, and S. litura [14] with the LC 50 values in the range of 35-290 ng/cm 2 .…”

Effects of Vip3AcAa+Cry1Ac Cotton on Midgut Tissue in Helicoverpa armigera (Lepidoptera: Noctuidae)

“…Such swelling of organelles and cells are consistent with those described for Bt and Bti in susceptible lepidopteran and mosquito larvae ( Knowles and Ellar 1987 , Yiallouros et al 1999 ). Spodoptera litura larvae fed with Vip3Aa toxin from B. thuringiensis WB5 occurred histopathological modifications, including vacuolization of the cytoplasm, cellular swelling, brush border membrane destruction and mitochondria swelling and deformation with disintegration and lysis of cristae of midgut epithelial cells ( Song et al 2016 ). In a study of the histopathology of larval midguts of Cry1Ac-susceptible H. armigera strain 96S after feeding on a diet with 0.5 µg/g of Cry1Ac or 50 µg/g of Vip3Aa, Zhang et al (2012b) found that Cry1Ac and Vip3Aa induced similar symptoms, but the changes induced by Vip3Aa occurred slower than those induced by Cry1Ac.…”

Functional characterization of Vip3Ab1 and Vip3Bc1: Two novel insecticidal proteins with differential activity against lepidopteran pests

“…Vips 1 and 2 are frequently active against coleopteran species of insects and function as binary insecticidal proteins utilizing ADP-ribosyltransferase activity to exert toxic effects on target insect cells 2 , 4 – 6 . Vip3 proteins have activity against a broad spectrum of economically important lepidopteran insects such as fall armyworm ( Spodoptera frugiperda ), beet armyworm ( Spodoptera exigua ), tobacco budworm ( Heliothis virescens ), corn earworm ( Helicoverpa zea ), and marginal activity against European corn borer ( Ostrinia nubilalis ) 3 , 7 – 9 . The Vip4 subgroup is composed of only one member, Vip4Aa1, with no known insecticidal activity 5 .…”