Abstract: Invertebrate intestinal mucin （IIM） is one of the important components of proteins on peritrophic membrane and plays a very important role in the protection against microbial infection of insects. The instestinal protein gene SeM-8 was amplified from 5th instar larvae of Spodoptera exigua by using RT-PCR technique. Sequence analysis showed that its open reading frame （ORF） is 2 703 bp in length, encoding a polypeptide of 900 amino acid residues with the predicted molecular mass of 95.7 kDa. SeM-8 protein shares 48%, 49% and 45% identities in amino acid with homologues from Helicoverpa armigera, Mamestra configurata and Plutella xylostella, respectively. Immuno-localization analysis showed that SeM-8 could be detected in egg, peritrophic membrane, midgut tissue and fecal pellets, but not detected in Malpighian tubules, fat body, salivary glands and haemolymph of 5th instar larvae. The results provided a foundation for pest management by using midgut as target.  

Key words: Spodoptera exigua, peritrophic membrane, invertebrate intestinal mucin, RCAE, cloning, expression, localization