Hop mosaic virus: complete nucleotide sequence and relationship to other carlaviruses

Excerpt

Hop mosaic virus (HpMV) is an important virus affecting hop (Humulus lupulus L.). It has been detected in all the major hop-growing regions of the world, and its negative impact upon growth, cone yield and levels of brewing acids has been documented [8]. HpMV belongs to the family Flexiviridae and the genus Carlavirus [1]. Typically, carlaviruses are rod-shaped viruses with a positive, single-strand RNA genome encapsulated by coat protein. The organisation of the genome includes six open reading frames (ORFs), a 5′ cap and a 3′ poly(A) tail. The structure and organisation of the genome is conserved among the carlaviruses [1]. ORF1 encodes the viral replicase and accounts for more than 70% of the length of the genome sequence. This ORF is composed of several functional domains which contribute to viral replication and which have a conserved amino acid sequence and order [7]. ORFs 2, 3 and 4 make up the triple gene block. These coding regions overlap and encode three proteins (TGBP 1, 2 and 3) that are thought to act in concert to enable virus movement between cells. ORF 5 encodes the coat protein and is overlapped by ORF 6, which encodes a nucleic acid-binding protein that has a putative role as a suppressor of RNA silencing [7]. The complete genome sequence has so far been reported for 19 carlaviruses (plus the complete coding sequence for one other) and varies from 8.2 to 9.1 kilobases (kb), excluding the poly(A) tail. …