Formation of Macromolecule Complex with Bacillus thuringiensis Cry1A Toxins and Chlorophyllide Binding 252-kDa Lipocalin-Like Protein Locating on Bombyx mori Midgut Membrane

Abstract

P252, a 252-kDa Bombyx mori protein located on the larval midgut membrane, has been shown to bind strongly with Bacillus thuringiensis Cry1A toxins (Hossain et al. Appl Environ Microbiol 70:4604-4612, 2004). P252 was also shown to bind chlorophyllide (Chlide) to form red fluorescence-emitting complex Bm252RFP with significant antimicrobial activity (Pandian et al. Appl Environ Microbiol 74:1324-1331, 2008). In this article, we show that Cry1A toxin bound with Bm252RFP and Bm252RFP-Cry1A macrocomplex, with both antimicrobial and insecticidal activities, was formed. The insecticidal activity of Bm252RFP-Cry1Ab was reduced from an LD₅₀ of 1.62 to 5.05 μg, but Bm252RFP-Cry1Aa and Bm252RFP-Cry1Ac did not show such reduction. On the other hand, the antimicrobial activity of Bm252RFP-Cry1Ab was shown to retain almost the same activity as Bm252RFP, while the other two complexes lost around 30% activity. The intensity of photo absorbance and fluorescence emission of Bm252RFP-Cry1Ab were significantly reduced compared to those of the other two complexes. Circular dichroism showed that the contents of Cry1Ab α-helix was significantly decreased in Bm252RFP-Cry1Ab but not in the other two toxins. These data suggested that the reduction of contents of α-helix in Cry1Ab affected the insecticidal activity of the macrocomplex but did not alter the antimicrobial moiety in the macrocomplex of Bm252RFP-Cry1Ab.

Effect of nutrient deprivation on the susceptibility ofGalleria mellonellalarvae to infection

“…Arylphorin functions in the storage of the aromatic amino acids but it also plays a central role in insect immunity. 20 Spot 5 showed homology to lipocalin, which functions in the immune response by binding to toxins and by complexing invading pathogens 21 and its expression was reduced by approximately 14% in starved larvae. Ferritin (spot 1) and transferrin precursor (spot 6) were reduced in expression by approximately 50% in food-deprived larvae.…”

Identification of ABCC2 as a binding protein of Cry1Ac on brush border membrane vesicles fromHelicoverpa armigeraby an improved pull‐down assay

“…However, it was shown that polycalin is not likely to be involved in toxicity in B. mori (Pandian et al. ).…”

“…Polycalin was reported to bind to Cry toxin in B. mori (Hossain et al 2004;Pandian et al 2008) and H. armigera (Angelucci et al 2008;Ma et al 2012). However, it was shown that polycalin is not likely to be involved in toxicity in B. mori (Pandian et al 2010).…”

Polycalin is involved in the toxicity and resistance to Cry1Ac toxin in Helicoverpa armigera (Hübner)

“…Later, it was found that the polycalin in H. armigera could bind with Cry1A and Cry2A toxins according to liquid chromatograghy–mass spectrometry (LC–MS)/MS, MS data, and binding results (Angelucci et al, 2008; Wang et al, 2019; Zhou et al, 2016). Importantly, some findings showed the macrocomplex of chlorophyllide (Chlide), polycalin and Cry1Ab can reduce the insecticidal activity when comparing with Cry1Ab alone (Pandian et al, 2010). In H. armigera , polycalin not only binds to Cry2Aa, but is also involve in the toxicity of Cry2Aa (Wang et al, 2019).…”