Gene structure and expression profile of Manduca sexta prophenoloxidase-activating proteinase-3 (PAP-3), an immune protein containing two clip domains.

Prophenoloxidase-activating proteinase-3 (PAP-3) is a component of the defence system in Manduca sexta. We have isolated genomic clones and elucidated the organization of this gene. The 3' end of exon 2, the entire exon 3 and the 5' end of exon 4 encode the two amino-terminal clip domains. Southern blot analysis suggested a single copy of the PAP-3 gene in the genome. We identified several putative immune-responsive elements in the upstream region. The PAP-3 gene is not highly expressed in the fat body during larval development until the wandering stage begins. The mRNA level is high in the epithelium, fat body and haemocytes. Tissue-specific alternative splicing occurs in the fat body and trachea. A bacterial injection markedly induced the gene expression in the fat body and haemocytes.