IDENTIFICATION AND PRELIMINARY CHARACTERIZATION OF A CHITINASE GENE IN THE AUTOGRAPHA-CALIFORNICA NUCLEAR POLYHEDROSIS-VIRUS GENOME

A functional chitinase gene (chiA) has been identified in the genome o f the Autographa californica nuclear polyhedrosis virus (AcMNPV). It i s expressed in the late phase of virus replication in insect cells. Hi gh levels of both endo- and exochitinase activity were detected by 12 hr p.i. and remained stable throughout infection. An AcMNPV chiA prote in-specific antibody was prepared using recombinant material prepared in bacteria. This was used to demonstrate that a product of approximat ely 58 kDa was synthesised in virus-infected cells. Immunofluorescence analysis of virus-infected cells showed that most chitinase was locat ed in the cytoplasm. Primer extension analysis of mRNA from AcMNPV-inf ected cells confirmed that transcription initiated from a baculovirus late start site (TAAG), 14 nucleotides upstream from the putative tran slation initiation codon. The predicted protein sequence of the AcMNPV chiA shares extensive sequence similarity with chitinases from bacter ia and, in particular, the Serratia marcescens chitinase A (60.5% iden tical residues). Phylogenetic analyses indicate that AcMNPV, or an anc estral baculovirus, acquired the chitinase gene from a bacterium via h orizontal gene transfer. (C) 1995 Academic Press, Inc.