Abstract: A full cDNA encoding an acetylcholinesterase (AChE, EC3.1.1.7) from the brown planthopper, Nilaparvata lugens (Homoptera: Delphacidae) was cloned and characterized. The complete cDNA (2 467 bp) contains a 1 938 bp open reading frame encoding 646 amino acid residues (GenBank accession no.AJ852420). The complete amino acid sequence of AChE deduced from the cDNA consists of 30 residues for the putative signal peptide and 616 residues for the mature protein with a predicted molecular weight of 69 418 D. The three residues (Ser242, Glu371 and His485) that putatively form the catalytic triad and six Cys that form intra-subunit disulfide bonds are completely conserved, and 10 out of the 14 aromatic residues lining the active site gorge of the AChE are also conserved. The deduced amino acid sequence is most similar to AChE of Nephotettix cincticeps with 83% amino acid identity. Phylogenetic analysis based on 30 AChEs from 23 insect species showed that the deduced AChE formed a cluster with 6 AChE2s. Additionally, the hypervariable region and amino acids specific to insect AChE2 also exist in N. lugens AChE. The results indicate that the AChE gene cloned in this work belongs to insect AChE2 subgroup, which are homologous to Drosophila AChE2.

Key words: Nilaparvata lugens, acetylcholinesterase, cDNA cloning, phylogenetic tree