Cloning of the gene for the capsid protein of potato leafroll virus

DNA complementary to the RNA of purified potato leafroll virus (PLRV) was synthesized and cloned into the lambda insertion vector NM1149. Overlapping PLRV-specific cDNA clones were isolated that represent some 80% of the viral genome. Sequences coding for the capsid protein were identified by subcloning size-selected cDNAs into the lambda expression vector gt11 and screening with PLRV-specific antisera. The gene for the viral capsid protein was shown to reside in the 3' terminal half of the genomic RNA. Sequence comparisons with the recently published genomes of the beet western yellows virus (BWYV) and the barely yellow dwarf virus (BYDV) reveal some 65% protein sequence homology between the capsid proteins of BWYV and PLRV and some 45% homology between BYDV and PLRV. Furthermore, it is evident that the structural organization of the PLRV genome in the CP gene region is similar to that of BWYV and BYDV.