Characterization And CDNA Cloning Of Midgut SeM-8 Protein From Spodoptera Exigua

The digestive tract in insect is commonly lined with a invertebrate unique structure,the peritrophic membrane(PM),playing very important role in the protection of insects from microbial infections,and PM is noncellular matrices of chitin and proteins. In this study,we report to cDNA cloning and sequencing of SeM-8 from mindgut of S. exigua larva. To clone and sequence the cDNA to obtain SeM-8,a cDNA expression library from S. exigua midgut was screened with several antibodies. The results of sequence analysis showed eight chitin binding proteins and two invertebrate intestinal mucins(IIM)from the library,which were similar to SeCBP and Spodoptera frugiperda PM protein 1 by using analysis of structure and function. The deduced protein from the cDNA clone,SeM-8,was a full-length of 2 703 bp and the open reading frame encoded a 95.7 kDa protein which 900 amino acid residues. Analysis of the amino acid sequence (GenBank accession GU255994)showed that the sequence similarity of SeM-8 to those identified from Helicoverpa armigera(Hübner), Mamestra configurata and Plutella xylostella was rates of 48%,49% and 45%,respectively. The protein not only was found in PM and midgut but was found in the late stage of eggs and fecal pellets. However,we didn't find it in malpighian tube,fat body,salivary glands and haemolymph from the 5th instar larvae.