Six of cadherins have been selected from the P. xylostella genome 52 open reading frames are annotated as cadherin-like genes. Compared to other 5 cadherins of P. xylostella (PxCads), PxCad1 has the highest homology with other lepidopteran insect cadherins and PxCad1 was expressed in all developmental stages specially in gut tissue. Expression of PxCad1 was suppressed by feeding its specific double-stranded RNA (dsRNA, 150ng/larva) and treatment of dsPxCad1 significantly reduced susceptibility to Bt Cry1Ac toxin.
To confirm the specific interaction between PxCad1 and Cry1Ac, a toxin-binding assay was performed using enzyme-linked immunosorbent assay (ELISA). The ELISA indicates that BBMV extracted from PxCad1-silenced P. xylostella have significantly lower binding activity to active form of Cry1Ac than control BBMV. Moreover, the analysis of the binding parameters showed that the toxin affinity (Kd) of the control BBMV extract (BBMV-dsCON) was 6.08 ± 0.84 nM, which was not much different to the affinity value (6.72 ± 0.81 nM) of the dsPxCad1 treatment. However, there was a remarkable difference in number of binding sites (Bmax), in which BBMV-dsCON extract had 1.61 ± 0.04, but the BBMV-dsPxCad1 extract had 0.88 ± 0.02.
Taken together, these results are suggest that PxCad1 is a functional receptor for Cry1Ac toxicity against P. xylostella larva.

• Youngjin Park(Department of Bioresource Sciences, Andong National University)
• Yonggyun Kim(Department of Bioresource Sciences, Andong National University)