In vitro synthesis and characterization of DNA complementary to potato spindle tuber viroid

When DNase-digested calf thymus DNA is used as primer, the RNA-directed DNA polymerase of avian myeloblastosis virus will accept potato spindle tuber viroid (PSTV) as a template for DNA synthesis. The DNA obtained hybridizes specifically to PSTV and low molecular weight RNA isolated from PSTV-infected plants; no hybridization to unrelated viral RNAs or tow molecular weight RNA isolated from uninoculated host plants was detectable. Purified PSTV cDNA is heterogeneous in length, but the mean chain length is approximately one-fourth that of PSTV. The kinetics of PSTV PSTV cDNA hybridization and the thermal denaturation profile of the resulting hybrids are consistent with the known molecular weight (1.27 x 10(5)) and G + C content (54.7%) of PSTV.