A Grapholita molesta (Lepidoptera: Tortricidae) cadherin in the 99C cadherin clade binds to Bacillus thuringiensis Cry1A proteins

Bt-cadherins, a particular type of midgut cadherins, act as receptors for Bacillus thuringiensis Cry1A pesticidal proteins. The aim of this work was to identify and validate the Cry1A cadherin receptor in Grapholita molesta (GmCad1). The GmCad1 gene was annotated by Blast genome mining using lepidopteran Bt-related cadherins. The phylogenetic analyses grouped GmCad1 with other Torticidae cadherins, in a different clade than the lepidopteran Bt-related cadherins. The in silico analysis of the GmCad1 showed a structure similar to that of the Bt-related cadherins, with 11 cadherin repeats (CRs), a transmembrane region, and an intracellular domain. The full-length mRNA sequencing confirmed GmCad1 expression in vivo in G. molesta guts. To validate the binding ability of Cry1A proteins to GmCad1, a cadherin fragment (CR7-CR11) was expressed and in vitro binding was studied demonstrating that Cry1Aa, Cry1Ab, and Cry1Ac bind to this region in a dose-dependent manner. In silico molecular docking analysis suggested that the interaction may involve mainly the Domains II of Cry1Ab and Cry1Ac, and the Domain III of Cry1Aa. This study provides the first evidence of a 99-C cadherin serving as a receptor for Cry1A in G. molesta.