A baculovirus homolog of a Cu/Zn superoxide dismutase gene

A gene with greater than 50% amino acid sequence identity to eukaryotic Cu/Zn superoxide dismutase genes (sod) was found at 19 map units in the genome of the baculovirus Autographa californica nuclear polyhedrosis virus (AcMNPV). This gene was transcribed into 1.4- and 1.5-kb RNAs late in virus infection. The two late RNAs have coterminal 3' ends but initiate from two different start points, both of which map to the central adenine of the sequence motif ATTAAG. The late gene product was found to be a low abundance 20-kDa polypeptide which was observed only upon partial purification by chloroform/ethanol extraction. Viruses with mutations in sod were able to replicate normally both in cell culture and in insect larvae. Viruses lacking an intact sod showed no evidence of a replication disadvantage even in the presence of paraquat, an inducer of superoxide anions. A viral-encoded superoxide dismutase (SOD) activity was not detected although endogenous insect SODs appeared to be induced in insect hemolymph and in other tissues following virus infection. The function of sod in the baculovirus infection process remains unclear.