Activity of Vip3Aa1 against Periplaneta americana

Abstract

<jats:title>Abstract</jats:title><jats:p><jats:italic>Bacillus thuringiensis</jats:italic> (<jats:italic>Bt</jats:italic>) is a well-known entomopathogen. In this study, we cloned the <jats:italic>vip3Aa1</jats:italic> gene from <jats:italic>Bt</jats:italic> strain GIM1.147 and investigated the insecticidal activity of <jats:italic>Bt</jats:italic> Vip3Aa1 protein produced by <jats:italic>Escherichia coli</jats:italic> against <jats:italic>Periplaneta americana</jats:italic> and <jats:italic>Blattella germanica</jats:italic>. The results showed that purified Vip3Aa1 exhibited an LC<jats:sub>50</jats:sub> at 24 h against <jats:italic>P. americana</jats:italic> and <jats:italic>B. germanica</jats:italic> of 0.182 mg·ml<jats:sup>-1</jats:sup> and 0.276 mg·ml<jats:sup>-1</jats:sup>, respectively. Investigations of its mode of action showed that Vip3Aa1 could be proteolyzed into a 62-kDa toxic protein by <jats:italic>P. americana</jats:italic> gut-soluble proteases. In addition, Vip3Aa1 caused severe damage to the columnar colon and the midgut, as observed through hematoxylin-eosin staining and scanning electron microscopy. The 62-kDa activated Vip3Aa1 protein could form ion channels in the colon and the midgut in vitro. Based on protease activity analysis, Vip3Aa1 at concentrations of 0.125 mg·ml<jats:sup>-1</jats:sup> and 0.031 mg·ml<jats:sup>-1</jats:sup> could downregulate the activities of glutathione S-transferase, α-NA esterase, trypsin, and chymotrypsin. This report provides the first description of the activity of Vip3Aa1 toxins toward <jats:italic>P. americana</jats:italic> and <jats:italic>B. germanica</jats:italic> and demonstrates that the mechanism through which Vip3Aa1 kills <jats:italic>P. americana</jats:italic> and <jats:italic>B. germanica</jats:italic> differs from that involved in the killing of lepidopteran insects.</jats:p>

Structural changes upon membrane insertion of the insecticidal pore-forming toxins produced by Bacillus thuringiensis

“…Initially, it was shown that Vip3 was lepidopteran specific. However, activity against other insect targets, such as the cockroach species Periplaneta americana and Blattella germanica ( 60 ), and the mosquito species Aedes aegypti ( 61 ), has been reported. Unlike Cry toxins, which accumulate in parasporal bodies inside the bacterial sporangium, Vip3 proteins are secreted by the Bt bacterium during the vegetative growth phase, and their production continues during the sporulation growth phase ( 62 ).…”

Ultrastructural and Morphological Observations of the External and Internal Structures of the Adult Midge <em>Culicoides grisescens</em> Edwards (Diptera: Ceratopogonidae)

“…Therefore, it is necessary to interpret more comprehensive and subtle morphological features in order to supplement and improve the morphological descriptions. There have been many reports on the hematoxylin -Eosin (HE) staining and paraffin sections of insects [10][11][12][13][14], however, there are fewer reports about the tissue structure of biting midges. In this paper, the morphology and ultrastructure of both adult sexes of C. grisescens were observed and described in detail by SEM, describing its characteristic morphology.…”