Infectious RNA derived by transcription from cloned cDNA copies of the genomic RNA of an insect virus.

RNA transcripts of cloned cDNA of the genomic RNAs of BBV (black beetle virus) are infectious to cultured cells of Drosophila melanogaster. Individual transcripts had approximately 10% of the infectivity of the corresponding authentic virion RNA. Progeny virus resulting from transcript infection was phenotypically indistinguishable from the progenitor virus used to generate the original cDNA forms as judged by sucrose density gradient sedimentation, specific infectivity, plaque morphology, and serology. Although the transcript RNAs used to produce this virus had 20 nonviral bases headed by a capping group at their 5' termini, these 20 bases were absent in the progeny viral RNAs. The cDNA forms, and therefore the resulting transcript RNAs, should be readily modifiable by the techniques of recombinant DNA technology both for viral studies and for the insertion of foreign genes into the viral genome and thus into the host cytoplasm.