Erratum to: Genomic classification of betanodavirus by molecular phylogenetic analysis of the coat protein gene

Abstract

The classification of betanodavirus into four species was reviewed including newer and well-characterised isolates. Six major clusters were identified, four of which were similar to the classic species. Two single isolate clusters were worth consideration as new species. Betanodaviruses are small (37 nm average) icosahedral viruses with two positive-stranded non-polyadenylated RNAs as its genome. RNA1 (3.1 kb) codes for the viral RNA-dependent RNA polymerase (protein A), while RNA2 (1.4 kb) codes for the coat protein [16]. A subgenomic RNA3 synthesized from RNA1 during early viral replication codes for protein B2 [17], which functions against the host RNA interference system [3, 8]. These viruses cause viral nervous necrosis (VNN) or viral encephalopathy and retinopathy (VER) in fin fishes. They were first identified as picorna-like virus particles [5] and later described as members of the family Nodaviridae [12]. Taxonomically, these viruses belong to the genus Betanodavirus of family Nodaviridae, with four species recognised so far [16] based on similarities in the variable region of the viral coat protein (CP) gene (nt 604-1030) [14]. The currently recognized species are Redspotted grouper nervous necrosis virus (RGNNV), Striped jack nervous necrosis virus (SJNNV), Tiger puffer nervous necrosis virus (TPNNV) and Barfin flounder nervous necrosis virus (BFNNV), with SJNNV as the type species. The preferred temperature ranges of members of these species are 25-30 C, 20-25 C, 20 C and 15-20 C, respectively. Over 40 fish species have been reported to be susceptible to betanodaviruses, and the number is steadily increasing [10, 13]. Since the first description 15 years ago, the taxonomy of betanodavirus has remained more or less the same irrespective of the huge number of virus isolates being reported from different geographical environments and from different fish hosts. Some modifications were proposed to the system [4, 11, 15, 19], but these have been largely restricted to the geographical area of the researcher. The study presented here is an attempt to analyze the global phylogenetic relationships among the viruses by comparing all isolates for which full-length coat protein (CP) gene ORF sequence information is available in the NCBI GenBank database. A short variable region in the CP gene is shown to be sufficient for determining the phylogenetics of these viruses [14], but the full-length CP gene ORF is used in this study to obtain more reliable results. Sequences of the full-length coat protein gene ORF of betanodaviruses were retrieved from the NCBI GenBank database with due care to include members of the species described in Eighth Report of the International Committee on Taxonomy of Viruses [16]. A total of 78 sequences were retrieved from the database. The sequences were labelled with their geographical location of isolation for ease of compilation for analysing the distribution pattern of the isolates included in this study. Betanodaviruses show high temperature specificity [6] and low host specificity [19], and this is expected to be reflected in their geographical distribution. The nucleotide and deduced amino acid sequences were aligned using the MUSCLE program [2] in MEGA software [18]. Neighbour-joining trees were C. P. Binesh (&) Sacred Heart College, Thevara, Cochin 682013, Kerala, India e-mail: bineshkanayi@gmail.com C. Greeshma Department of Life Sciences, Calicut University, Thenjippalam, Malappauram, Kerala, India e-mail: greeshmakongatta@gmail.com 123 Arch Virol (2013) 158:1589–1594 DOI 10.1007/s00705-012-1549-7