Abstract: Peritrophic membrane (PM) is an acellular semipermeable membrane secreted by midgut epithelial cells in most insects. The insect intestinal mucin is the most important component of PM. A full-length cDNA clone HM72 encoding an intestinal mucin HM72 was identified by screening Helicoverpa armigera midgut cDNA expression library with the polyclonal antiserum against H. armigera PM proteins. The full-length cDNA of HM72 is 2 888 bp in length (GenBank accession no. HM017910), containing an open reading frame (ORF) of 2 469 bp, followed by an AT-rich untranslated region and a putative polyadenylation signal (AATTAA) located at 19 bp upstream of the polyA tail. The deduced protein sequences show that the HM72 is an acidic protein, and is synthesized as a preprotein of 823 amino acid residues with a 16-amino acid signal peptide. After removal of the signal peptide, the secreted HM72 protein is predicted to have a molecular weight of 84.2 kDa and isoelectric point of 3.63. The secreted HM72 has five chitin binding domains, one mucin domain and two glycine-aspartic acid-rich domain. HM72 was recombined into pET21b vector, and expressed by IPTG induction. Western blot analysis revealed that HM72 was more abundant in the exuviae, fecal pellets, peritrophic membrane and the midgut of H. armigera, and was secreted by cells from whole midgut. HM72 was not found in the larval fat bodies, integument, malpighian tubules, salivary glands, midgut fluid and hemolymph. This study provides a foundation for the research of bio-control associated novel genes of H. armigera and the perfection of the insect peritrophic membrane theory.

Key words: Helicoverpa armigera； midgut, epithelial cells, peritrophic membrane, intestinal mucin, cDNA expression library, histolocalization