Functional characterization of chitinase from Cydia pomonella granulovirus.

Baculovirus chitinases (V-CHIAs) play a crucial role in the terminal liquefaction of virus-infected larvae after death. Although v-chiAs from nucleopolyhedroviruses (NPVs) have been well characterized, little is known about v-chiAs from granuloviruses (GVs). We characterized the v-chiA of Cydia pomonella GV (CpGV) by constructing a recombinant Bombyx mori NPV (BmNPV) in which BmNPV v-chiA was replaced by CpGV v-chiA (103CpGV virus). CpGV v-chiA encoded an approximately 70-kDa chitinase with an exo-type substrate preference. CpGV V-CHIA lacked a C-terminal KDEL endoplasmic reticulum retention motif and was suggested to be a secretory protein. Terminal host liquefaction of B. mori larvae and proper folding of BmNPV-encoded cysteine protease (BmNPV V-CATH) were observed following infection with 103CpGV, indicating that CpGV v-chiA is able to compensate for the absence of its BmNPV counterpart. Our data suggest that the molecular interaction between V-CHIA and V-CATH may be conserved across a broad range of lepidopteran GVs and NPVs.