Barley yellow dwarf virus RNA requires a cap-independent translation sequence because it lacks a 5' cap

A 3' translation enhancer (3'TE) sequence that facilitates cap-independent translation is located near the 3' end of barley yellow dwarf luteovirus RNA. Here, we show that the 3'TE is required for translation of the viral genome and thus for viral replication. Antisense inhibition showed that the 3'TE has significant secondary structure and is required for translation of virion RNA from infected plants and uncapped genomic transcripts but not for translation of capped transcripts. Direct end-labeling of RNAs verified the absence of a 5' modification on virion RNA. Thus barley yellow dwarf virus differs from related viruses by having neither a genome-linked protein nor a 5' cap.