Requirement for eukaryotic translation initiation factors in cap-independent translation differs between bipartite genomic RNAs of red clover necrotic mosaic virus

Abstract

The bipartite genomic RNAs of red clover necrotic mosaic virus (RCNMV) lack a 5′ cap and a 3′ poly(A) tail. RNA1 encodes viral replication proteins, and RNA2 encodes a movement protein (MP). These proteins are translated in a cap-independent manner. We previously identified two cis-acting RNA elements that cooperatively recruit eukaryotic translation initiation factor (eIF) complex eIF4F or eIFiso4F to RNA1. Such cis-acting RNA elements and host factors have not been identified in RNA2. Here we found that translation of RNA1 was significantly compromised in Arabidopsis thaliana carrying eif4f mutation. RNA1 replicated efficiently in eifiso4f1 mutants, suggesting vigorous translation of the replication proteins from RNA1 in the plants. In contrast, MP accumulation was decreased in eifiso4f1 mutants but not in eif4f mutants. Collectively, these results suggest that RCNMV uses different eIF complexes for translation of its bipartite genomic RNAs, which may contribute to fine-tuning viral gene expression during infection.