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Identification of Henosepilachna vigintioctomaculata (Coleoptera: Coccinellidae) midgut putative receptor for Bacillus thuringiensis insecticidal Cry7Ab3 toxin

Song, Ping, Wang, QinYing, Nangong, ZiYan, Su, JunPing, Ge, DongHua
Journal of invertebrate pathology 2012 v.109 no.3 pp. 318-322
Bacillus thuringiensis, Epilachna, cadherins, death, epithelium, histopathology, ingestion, insecticidal properties, larvae, matrix-assisted laser desorption-ionization mass spectrometry, midgut, trypsin
Bt WZ-9 strain, containing a single Cry7Ab3 toxin, had effective insecticidal activity against larvae of Henosepilachna vigintioctomaculata. By incubation with larvae midgut homogenate and trypsin in vitro, 130kDa Cry7Ab3 protoxin was degraded into the ∼75kDa proteinase-resistant fragments. In vivo analysis, 130kDa Cry7Ab3 protoxin was also processed into ∼75kDa fragment. Histopathological observations indicated that Cry7Ab3 ingestion by H. vigintioctomaculata larvae causes acceleration in the blebbing of the midgut epithelium cells into the gut lumen and eventual lysis of the epithelium cells resulting in larval death. A ligand blotting experiment demonstrated that Cry7Ab3 toxin bound a 220kDa BBMV protein. This receptor protein was identified as cadherin by matrix assisted laser desorption-time of flight-mass spectrometry (MALDI-TOF-MS). The cadherin protein may be the receptor of Cry7Ab3. The data obtained may contribute to a better understanding of the mechanism of Cry7Ab3 toxin against H. vigintioctomaculata larvae.