ABSTRACT
By the genome size and number of genes, the Leviviridae RNA phages are belonging to the smallest organisms that are able nevertheless to regulate their macromolecular syntheses close to perfection. This chapter presents the general genome characteristics including peculiarities of the genome organization and location of the genes, as well as differences in the genomic organization among different phage species. The genomes of the genera Levivirus and Allolevivirus demonstrate a strict difference that generates new Allolevivirus protein, namely, a minor A1 protein. The latter is nothing else than a C-terminally extended coat protein, which appears as a result of ribosomal read-through at a leaky opal termination codon of the Allolevivirus coat gene and is found essential for the formation of viable virions in vivo. The up-to-date analysis of the full-length RNA phage genomes and their phylogenetic relatedness is presented.
