Abstract: Phenoloxidase plays an important role in d efense mechanisms in insect immunity. The complemental deoxyribonuc leic acid （cDNA） of Bombyx mandarina prophenoloxidase (PPO) gen e was cloned by means of reverse transcription polymerase chain reaction （RT-P CR） and rapid amplification of cDNA ends (RACE). The cDNA was 2 134 bp in l ength a nd contained an open reading frame (ORF) of 2 082 bp which encoded 693 amino aci d residues．The deduced amino acid sequence showed a high identity to the report ed sequence of PPO2 from other Lepidopterous insects and shared the typical stru ctural features of PPO from other insects. The results of RT-PCR showed that PP O mRNA was expressed in the integument, haemocyte, head, testis, ovary, fat body and midgut of 5th instar larvae and at different developmental stages of B. m andarina. These results provide molecular basis for further studying the funct ion of ppo gene inB. mandarina.

Key words: Bombyx mandarina, prophenoloxidase gene, cloning, sequence analysis, tissue expression