Zhang Li-li;Liang Ge-mei;Gao Xi-wu;Cao Guang-chun;Guo Yu-yuan

Chinese Acad Agr Sci, Inst Plant Protect, State Key Lab Biol Plant Dis & Insect Pests, Beijing 100193, Peoples R China;China Agr Univ, Coll Agr & Biotechnol, Beijing 100193, Peoples R China

beta-1,3-galactosyltransferase;Cry1Ac;resistance;Helicoverpa armigera;RNAi

Carbohydrate chains are the principal antigens by which Bacillus thuringiensis (Bt) identify receptor proteins. The interaction between the antigen and Bt causes a pore in the membrane of midgut epithelial cells of insects. Receptor proteins, such as aminopeptidase N and alkaline phosphatase, are glycoproteins. Cadherin is another cell surface receptor protein which has potential glycosylation sites. Glycosyltransferase is very important for the synthesis and modification of receptor proteins. It can indirectly influence the function of Bt. The 1 950 bp full-length cDNA encoding beta-1,3-galactosyltransferase was cloned from the the midgut of Helicoverpa armigera by degenerative PCR combined with RACE techniques (GAL-Harm, GenBank accession no.: GQ904195.1) with two potential N-glycosylation sites ((NNTI160)-N-157 and (NKTL275)-N-272). Protein sequence alignments revealed that H. armigera beta-1,3-galactosyltransferase shared high identity with beta-1,3-galactosyltransferase in other insect species. The expression level of the beta-1,3-galactosyltransferase gene in Cry1Ac-resistant H. armigera larvae was 9.2-fold higher than that in susceptible strain. The function of beta-1,3-galactosyltransferase was investigated using RNAi technique. The result showed Cry1Ac enhanced the toxicity against the siRNA-treated larvae compared with non-siRNA-treated ones, which indicated beta-1,3-galactosyltransferase played an important role for the insecticidal toxicity of Cry1Ac in H. armigera.