title: Gene expression of a novel defensin antimicrobial peptide in the silkworm, Bombyx mori.
abstract: cDNA encoding a novel defensin (BmDefensinB) was cloned from the fat body of the silkworm, Bombyx mori, and gene expression was analyzed. BmDefensinB showed typical structural characteristics of invertebrate defensins. Phylogenetic and bootstrap analyses indicated that it has no orthologs, whereas previously reported BmDefensinA is the ortholog of Spodoptera frugiperda (Sf)Spodoptericin. The BmDefensinB gene was expressed tissue-specifically in the fat body and was strongly activated by bacteria such as Escherichia coli and Bacillus subtilis, and by an entomopathogenic fungus Beauveria bassiana. In contrast, the BmDefensinA gene was expressed to a much lesser extent. Expression of the BmDefensinB gene was strongly stimulated by B. mori Rel proteins RelB and Relish, supporting the observation that this gene is activated by E. coli, B. subtilis, and B. bassiana. These results suggest that BmDefensinB gene expression is controlled through both the Toll and the Imd pathway, and that this gene plays an important role in B. mori immune reactions against infection by bacteria and fungi.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Kaneko
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Tanaka
authors.forename: Jun
authors.initials: J
authors.lastname: Ishibashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Iwasaki
authors.forename: Minoru
authors.initials: M
authors.lastname: Yamakawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000378:metabolism; D023181:Antimicrobial Cationic Peptides / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D012831:Bombyx / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D023082:Defensins / Q000235:genetics* / Q000378:metabolism; D005216:Fat Body / Q000378:metabolism; D015870:Gene Expression; D017344:Genes, Insect; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny
chemical_list: D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D018076:DNA, Complementary; D023082:Defensins; D019476:Insect Proteins; D010455:Peptides