CHARACTERIZATION OF CITRUS TRISTEZA VIRUS SUBGENOMIC RNAS IN INFECTEDTISSUE

Citrus tristeza virus (CTV) specific RNAs extracted from infected citr us tissue were analyzed by Northern blot hybridization. RNAs were char acterized by size and identified using cDNA probes specific to nine op en reading frames (ORFs) identified by the analysis of sequence obtain ed from cDNA clones of the T36 isolate of CTV. Sequence specific cDNA probes identified the genomic RNA as well as subgenomic RNAs represent ing the p33, p65, p61, p27, p25, p18, p13, p20, and p23 ORFs in extrac ts of total or double-stranded RNA (dsRNA) isolated from infected tiss ue. A probe derived from the 3' terminal ORF (p23) hybridized to each of these subgenomic RNAs, indicating that the RNAs are 3' coterminal. The relative amounts of the different subgenomic RNAs varied widely. T he RNAs for the p20 and p23 ORFs were the most abundant and surpassed the amount of the p25 or capsid protein specific subgenomic RNA. The n umber and sizes of the CTV subgenomic RNAs were the same in total RNA and dsRNA preparations. Propagation of T36 in seven different citrus h osts did not alter the pattern of subgenomic RNAs.