CLONING OF MESSENGER-RNA SEQUENCES FOR 2 ANTIBACTERIAL PEPTIDES IN A HEMIPTERAN INSECT, RIPTORTUS-CLAVATUS

Escherichia coil injection rapidly induced bactericidal activity in th e hemolymph of a hemipteran insect, Riptortus clavatus. This activity reached its maximum at 9 hr after injection and thereafter declined sl owly. Two types of cDNA clones involved in this response were isolated by differential screening. The predominant type encoded for an open r eading frame of 678 amino acids, which consisted of fourteen tandem re peats. Each repeat was rich in charged residues and had a proline-rich region which had striking sequence similarities to proline-rich antib acterial peptides from other insect species, indicating these clones e ncode a multipeptide precursor of antibacterial peptides. The other ty pe encoded for a glycine-rich peptide similar to a known antibacterial peptide as well. Northern blot analyses revealed rapid induction of m RNAs corresponding to these clones after the injection. To our knowled ge, this is the first report on the mRNA sequences of antibacterial pe ptides of hemimetabolous insects, and the second report on the occurre nce of multipeptide precursor structure in insect antibacterial peptid es.