cDNA cloning and gene expression of cecropin D, an antibacterial protein in the silkworm, Bombyx mori.
We have isolated a cDNA clone encoding a cecropin D precursor from the fat body of Bombyx mori larvae immunized with bacteria by means of differential display. The cDNA contains 298 bp with a coding region of 183 bp for 61 amino acids plus a termination codon (TAG), a 5'-untranslated region of 36 bp, and a 3'-untranslated region of 79 bp including the poly(A) tail. There is a polyadenylation signal sequence of AATAAA at position 266, 43 nucleotides downstream from the termination codon TAG. The homology of the deduced amino acids is greater to the cecropin D precursor from Hyalophora cecropia (67% identity) than to the precursors of cecropins A and B from B. mori (49% to both). Northern blotting analyses reveal that the gene expression of cecropin D is detectable by 4 h after the bacterial injection and reaches the maximal level at 24 h. That high level is maintained up to 48 h post-immunization. Additionally, the gene is expressed mainly in the fat body and slightly in hemocytes, but it is undetectable in other tissues such as the midgut, the Malpighian tubule and silk gland.
Laboratory of Biological Defense, National Institute of Sericultural and Entomological Science, Ibaraki, Japan.
J
J
Yang
S
S
Furukawa
A
A
Sagisaka
J
J
Ishibashi
K
K
Taniai
T
T
Shono
M
M
Yamakawa
D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics*; D018076:DNA, Complementary / Q000378:metabolism*; D015870:Gene Expression; D019476:Insect Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D014018:Tissue Distribution
D000900:Anti-Bacterial Agents; D018076:DNA, Complementary; D019476:Insect Proteins; C036149:cecropin D protein, Hyalophora cecropia