Organization and expression of single stranded positive sense RNA plant viruses

Abstract

a majority of plant viruses have positive-sense RNA as their genome. These viruses are classified as mono-, bi- or tripartite based on the presence of 1, 2, or 3 RNA segments as their genomes. The constraints imposed by eukaryotic protein synthesizing machinery for translation of only the first 5' ORF as well as the need for optimal utilization of the limited genetic material necessitate these viruses to evolve different strategies to express their genes. These strategies include termination at a non-conventional stop signal, read through of leaky termination codon, polyprotem processing, frame shifting, generation of subgenomic mRNAs and internal initiation. Despite wide variation in particle morphology, host plant, vector transmission, etc., an analysis of the genomic sequence and strategies of expression in these viruses has led to their classification into a limited number of super-groups. Many inter-viral mechanisms of viral replication, trans location, etc. Determination of genomic sequences of a large number of viruses will help in further strengthening the established evolutionary relationship among various groups pf plant viruses.