IDENTIFICATION OF THE GENE ENCODING THE MAJOR CAPSID PROTEIN OF INSECT IRIDESCENT VIRUS TYPE-6 BY POLYMERASE CHAIN-REACTION

The gene encoding the major capsid protein of Chilo iridescent virus ( CIV) has been identified by PCR using oligonucleotide primers correspo nding to different regions of the major capsid proteins of Tipula irid escent virus (TIV) and iridescent virus 22 (IV22). A DNA fragment of 0 .5 kbp was amplified using two oligonucleotide primers corresponding t o the amino acid positions 146 to 153 and 304 to 313 of the major caps id protein of TIV, respectively. The radioactively labelled DNA fragme nt derived from PCR was hybridized to a CIV gene library. This analysi s revealed that only the EcoRI CIV DNA fragment X [2.85 kbp; 0.589 to 0.603 viral map units (m.u.)] hybridized to the amplified DNA fragment . An RNA transcript of about 1.5 kb was identified when the PCR produc t was used as a hybridization probe. The same RNA transcript was detec ted when the EcoRI fragments X and Q (5.9 kbp; 0.603 to 0.631 viral m. u.) were used as probes. This indicates that the expected gene is loca ted within map coordinates 0-589 to 0-631 and harbours part of the DNA sequences of fragments Q and X. The analysis of the DNA sequences of this particular region of the CIV genome revealed the presence of one open reding frame of 1401 bp. The DNA sequences of this region encode a protein of 467 amino acid residues with an M(r) of 51.4K. A high deg ree (64.7 %) of amino acid sequence identity was detected between the major capsid protein of TIV and/or IV22 and the amino acid composition of the identified CIV protein.