The ATP‐binding cassette transporter subfamily C member 2 in Bombyx mori larvae is a functional receptor for Cry toxins from Bacillus thuringiensis

Abstract

Bacillus thuringiensis is the most widely used biopesticide, and its Cry toxin genes are essential transgenes for the generation of insect‐resistant transgenic crops. Recent reports have suggested that ATP‐binding cassette transporter subfamily C2 (ABCC2) proteins are implicated in Cry intoxication, and that a single amino acid insertion results in high levels of resistance to Cry1 toxins. However, there is currently no available direct evidence of functional interactions between ABCC2 and Cry toxins. To address this important knowledge gap, we investigated the role of Bombyx mori ABCC2 (BmABCC2) or its mutant from a Cry1Ab‐resistant B. mori strain on Cry1A toxin action. When we expressed BmABCC2 ectopically on Sf9 cells, it served as a functional receptor, and the single amino acid insertion found in BmABCC2 from Cry1Ab‐resistant larvae resulted in lack of susceptibility to Cry1Ab and Cry1Ac. Using the same expression system, we found that Bo. mori cadherin‐like receptor (BtR175) conferred susceptibility to Cry1A toxins, albeit to a lower degree than BmABCC2. Coexpression of BtR175 and BmABCC2 resulted in the highest cell susceptibility to Cry1A, Cry1F, and even the phylogenetically distant Cry8Ca toxin, when compared with expression of either receptor alone. The susceptibility observed in the coexpressing cells and that in Bo. mori larvae are likely to be correlated, suggesting that BtR175 and BmABCC2 are important factors determining larval susceptibility. Our study demonstrates, for the first time, Cry toxin receptor functionality for ABCC2, and highlights the crucial role of this protein and cadherin in the mechanism of action of Cry toxin.

Down-regulation of a novel ABC transporter gene (Pxwhite) is associated with Cry1Ac resistance in the diamondback moth, Plutella xylostella (L.)

“…Recently, mutations of an ABCC gene (ABCC2) have been found to be linked with Bt Cry resistance in several lepidopteran insects (Gahan et al, 2010;Baxter et al, 2011;Atsumi et al, 2012;Park et al, 2014;Xiao et al, 2014), and it has been speculated that ABCC2 might play a role in facilitating the insertion of oligomeric pre-pore structure into the insect midgut membrane in the mode of action of Bt Cry toxins (Heckel, 2012). ABCC2 has recently been proved to be a functional Cry toxin receptor in B. mori (Tanaka et al, 2013), and we suspect that the role of the possibly formed white heterodimer in P. xylostella is similar to that of ABCC2 in B. mori. However, a recent study has indicated that the pre-pore oligomer does not require additional receptors in order to insert into the midgut membrane (G omez et al, 2014), suggesting that ABCC2 or white heterodimer proteins may be involved in other steps resulting in Cry toxin activity rather than being involved in the insertion of the toxin into the membrane.…”

Sodium Solute Symporter and Cadherin Proteins Act as Bacillus thuringiensis Cry3Ba Toxin Functional Receptors in Tribolium castaneum

“…In Lepidoptera, it has been demonstrated that interaction of Cry1 toxins with aminopeptidase N (APN) and cadherin (CAD)-like) midgut proteins (2, 3) is required for toxic action, and alkaline phosphatase and ABC transporter have also been proposed as Cry1 receptors (4,5). In mosquito larvae, homologous APN, CAD-like, and alkaline phosphatase proteins have been described as Cry11 and Cry4 receptor proteins (6), and in Coleoptera a cadherin-like protein has been demonstrated to act as a Cry3Aa receptor (7).…”

Construction of a simple evaluation system for the intestinal absorption of an orally administered medicine using <i>Bombyx mori</i> larvae

“…However, the function of most ABC transporter genes has not been analyzed without the B. mori ABC transporter subfamily C member 2 (BmABCC2), which relays transported Cry toxins from Bacillus thuringiensis (22). Aditionally, a single amino acid mutation of BmABCC2 causes a resistance to Cry toxin in B. mori (23).…”