Related RNAs in lepidopteran cells after in vitro infection with Hyposoterdidymator virus define a new polydnavirus gene family

In the present study, we describe the isolation and the characterization of three different Hyposoter didymator virus (HdV) lepidopteran host-expresse d genes, the products of which might interfere with the host physiology dur ing parasitism. In this report, we study the expression of HdV genes in Sf9 cells infected with HdV since results indicate that the Sf9 model mimics t o some extent the in vivo model and may be utilized to study expression of HdV genes in lepidopteran host cells. This system allowed us to isolate thr ee HdV-specific cDNAs, termed M24, M27, and M40. cDNA nucleotide sequence a nalysis demonstrated significant regions of homology. The three cDNAs displ ayed repeated sequences arranged in tandem array that might have evolved th rough domain duplication. Similar to other previously described polydnaviru s host-expressed genes, two intron positions have been found in the M24 lea der region. The cDNAs corresponded to RNAs of 1.6, 1.6, and 2.3 kb that are also detected in parasitized Spodoptera littoralis larvae. They are encode d by different genes likely located on different HdV DNA molecules. Corresp onding RNAs are detected early postinfection and remain detectable for at l east 10 days postinfection. They encode secreted glycine- and proline-rich proteins. An antiserum raised against a baculovirus recombinant M24-encoded protein detected similar proteins in the culture medium of infected lepido pteran cells and in parasitized host hemolymph. We propose that the three c loned genes belong to an HdV gene family specifically expressed in parasiti zed lepidopteran hosts, (C) 1999 Academic Press.