Effects of inactivation of the coat protein and movement genes of Tomato bushy stunt virus on early accumulation of genomic and subgenomic RNAs

Abstract

Accumulation of RNA of Tomato bushy stunt virus (TBSV) was examined within the first few hours after infection of Nicotiana benthamiana protoplasts to determine the influence of the coat protein (CP), the movement-associated proteins P22 and P19 and RNA sequences at very early stages of replication. The results showed that P19 had no effect on early RNA replication, whereas the absence of CP and/or P22 expression delayed RNA accumulation only marginally. Removal of CPcoding sequences had no added negative effects, but when the deletion extended into the downstream p22 gene, it not only eliminated synthesis of subgenomic RNA2 but also delayed accumulation of genomic RNA by 10 h. At times beyond 20 h post-transfection, RNA accumulated to normal high levels for all mutants. This illustrates that TBSV RNA sequences that have negligible impact on overall RNA levels observed late in infection can actually have pronounced effects at very early stages.

Further Molecular Characterization and Effect on Host Photosynthetic Pigments and Carbohydrate Pools of an Egyptian Isolate of TBSV

“…The start codon for translation of sgRNA1 is in a favourable context to yield high levels of CP [7]. Time-course experiments at an early time-point after infection suggest that transcription of sgRNA1, and subsequent accumulation of CP, is relatively late events [34]. This is in agreement with a model that virion assembly in infected cells occurs after the infection has already progressed to neighboring cells.…”

“…The nucleotide sequence when submitted to the NCBI nucleotide sequence database, GenBank was accepted and received an accession number JX418297. Accumulation of sgRNA2 is a relatively early event in TBSV infection [34]. P22 and P19 are known to be located in a nested form at the 3'-proximal end and translation of the nested P22 and P19 genes from sgRNA2 occurs via contextdependent ribosome leaky scanning [7,8].…”

Analysis of a 3′-translation enhancer in a tombusvirus: A dynamic model for RNA–RNA interactions of mRNA termini

“…Interestingly, even if the sg mRNA 59-adapter sequences were able to interact with the 39CITE in the context of the genome, the proposed 59-end loading mechanism for TBSV translation would not support initiation events at these internal sites. Preventing such events may be important, as spurious initiations within the viral genome could be deleterious to the virus by interfering with the timing and/or amount of 39-proximally encoded proteins produced-which, in TBSV, are controlled primarily at the level of sg mRNA transcription (Zhang et al 1999;Qiu and Scholthof 2001;Choi and White 2002;Lin and White 2004).…”

Subgenomic mRNA transcription in Tombusviridae

“…In the tombusvirus Tomato bushy stunt virus (TBSV), sg mRNA2 transcription precedes that of the larger sg mRNA1. 11 Conversely, in the necrovirus Tobacco necrosis virus-A, the larger sg mRNA1 appears earlier than sg mRNA2. 12 Thus, the relative size of the sg mRNA does not dictate the timing of its appearance.…”