Sequence reversion in the distal element of Potato leafroll virus coat protein gene stop codon indicates a strong bias toward the stem loop structure to allow efficient read-through    
Y. XU (1), S. Gray (2) (1) Cornell University, U.S.A.; (2) Cornell University; USDA-ARS, Robert W. Holley Center for Agriculture and Health, U.S.A.

Translational read-through of the capsid protein UAG stop codon is an evolutionarily conserved feature that members of the Luteoviridae have adopted as a strategy to produce the minor capsid protein referred to as the readthrough protein (RTP). Distinct domains of the RTP of Potato leafroll virus (PLRV) have been associated with the regulation of virus movement and tissue tropism in plant hosts, and in aphid transmission. The elements regulating PLRV RTP expression are not well understood. We investigated the requirements for this process. A distal element 90 nucleotides in length and predicted to have a complex stem loop structure was located 640 nucleotides downstream of the CP stop codon. Site directed mutational analyses of this element confirmed that conserved nucleotides in the loop and in paired regions of the stem are critical for translational read-through. Deletion and point amino acid mutagenesis suggest that neither the distance between the stop codon and the distal element nor the size of the critical loop within the element are important for translational read-through. Furthermore, reversions of altered sequences that restore critical stem and loop structures are common after long-term infection of Solanum sarrachoides or Nicotiana benthamiana, suggesting there is a strong selection for efficient read-through. Importantly, by substitution and deletion mutagenesis analysis with the related Cereal yellow dwarf virus-RPV, we found the direct RNA communication between this distal element and the cysteine-rich domain is required for efficient translation of the RTP. 

Abstract Number: P12-404
Session Type: Poster