Antibacterial properties and partial cDNA sequences of cecropin-like antibacterial peptides from the common cutworm, Spodoptera litura

The antibacterial properties and cDNA sequences of two types of antibacteri al peptides from the haemolymph of immunized common cutworm, Spodoptera lit ura larvae, were determined. Since the primary structures of peptides deduc ed from cDNA sequences showed significant homologies to cecropins A and B: they were named as Spodoptera cecropins A and B. Spodoptera cecropins were broadly effective against Gram-positive and negative bacteria. They also re tained antibacterial activities in all conditions tested (at pH 5.6-8.0 and in the presence of 50-150 mM NaCl) that was adapted to confirm the antibac terial properties of Spodoptera cecropins. These results indicate that the change of pH and the increase of salt concentration in the media do not inf luence the activities of Spodoptera cecropins. For the reverse transcriptio n (RT)-polymerase chain reaction (PCR) to obtain the complete primary seque ncer the primer designed according to the conserved region of the cecropin leader sequences was used, which was determined by the comparison of the cD NA sequences of known cecropins. The results from RT-PCR presented that the partial cDNAs of Spodoptera cecropins A and B encode 57 and 58 amino acids , including the sequences of mature peptides, respectively. In addition, No rthern blot analysis with P-32-labeled PCR product coding for Spodoptera ce cropin A revealed that Spodoptera cecropin genes are expressed in immunized fat body, but not in normal fat body, (C) 2000 Elsevier Science Inc. All r ights reserved.