Molecular cloning and expression patterns of a serpin-2 from the beet armyworm, Spodoptera exigua

Serpins; are known to play a critical role in insect immunity and physiology. Here, we present a 1,296 nucleotide sequence of a serpin gene from the beet armyworm, Spodoptera exigua. The putative gene product is a 376 amino acid protein containing the conserved reactive center loop (RCL) residues found in serpin, and has the highest identity to Bombyx mori serpin-2 (67 %). In addition, it has a homology to serpins of other insects such as Lonomia obliqua (66 %), Manduca sexta (52 %), and Plutella xylostella (41 %). RT-PCR analysis shows that it is not induced in response to laminarin and lipoteichoic acid (LTA), whereas SeCecropinB is induced under the same condition. In addition, it is not induced by nucleopolyhedrosis virus of S. exigua (SeNPV), whereas SeCecropinB and inhibitor of apoptosis (SeNPV-IAP) are induced by SeNPV infection. The lack of dramatic induction of S. exigua serpin-2 under these immune challenged conditions suggests that it may have an unknown function during the developmental stages albeit it remains to he further elucidated.