Molecular Characterization and Variation of the Broad bean wilt virus 2 Isolates Based on Analyses of Complete Genome Sequences

Abstract

The full-genome sequences of fourteen isolates of Broad bean wilt virus 2 (BBWV2), collected from broad bean, pea, spinach, bell pepper and paprika plants in Korea during the years 2006–2012, were determined and analyzed comparatively along with fifteen previously reported BBWV2 genome sequences. Sequence analyses showed that RNA-1 and RNA-2 sequences of BBWV2 Korean isolates consisted of 5950–5956 and 3568–3604 nucleotides, respectively. Full-length genome sequence-based phylogenetic analyses revealed that the BBWV2 Korean isolates could be divided into three major groups comprising GS-I (isolates BB2 and RP7) along with isolate IP, GS-II (isolates BB5, P2, P3 and RP3) along with isolate B935, and GS-III including 16 BBWV2 Korean isolates. Interestingly, GS-III appears to be newly emerged and predominant in Korea. Recombination analyses identified two recombination events in the analyzed BBWV2 population: one in the RNA-1 of isolate K and another one in the RNA-2 of isolate XJ14-3. However, no recombination events were detected in the other 21 Korean isolates. On the other hand, out of 29 BBWV2 isolates, 16 isolates were found to be reassortants, of which each RNA segment (i.e. RNA1 and RNA2) was originated from different parental isolates. Our findings suggested that reassortment rather than recombination is a major evolutionary force in the genetic diversification of BBWV population in Korea.

Viral Strain-Specific Activation of Pathogen-Associated Molecular Pattern-Triggered Immunity Enhances Symptom Severity in Broad Bean Wilt Virus 2 Infection

“…Broad bean wilt virus 2 is an emerging virus in various economically important crops worldwide. BBWV2 has a wide host range, and the viral strains isolated from different hosts are genetically and pathogenically differentiated (Ferrer et al, 2011;Kwak et al, 2013aKwak et al, , 2016. Symptomatic variation among different virus strains in a host plant is primarily due to strainspecific viral proteins.…”

“…While more than 100 viruses infect pepper plants worldwide (Kenyon et al, 2014), broad bean wilt virus 2 (BBWV2; genus Fabavirus, family Secoviridae) is an emerging virus in many global areas (Kwak et al, 2013a,b;Ferriol et al, 2014). The incidence of BBWV2 in pepper has increased rapidly over the past decade, because the virus can be easily transmitted by aphids and infect a wide range of plants, including various weed hosts that inhabit areas near pepper fields (Kwak et al, 2013a;Kim et al, 2014a). The BBWV2 genome is composed of two segments of positivesense single-stranded RNAs, RNA1 (~5.8 knt) and RNA2 (~3.3 knt; Ferrer et al, 2011).…”

A Plant Virus-Based Vector System for Gene Function Studies in Pepper

“…Pepper seedlings at different ages (2, 3, and 4 weeks old) were selected for inoculation. For Agrobacterium tumefaciensmediated inoculation of recombinant BBWV2 clones, plasmid DNA of each BBWV2 construct was transformed into A. tumefaciens strain EHA105, and agroinfiltration was performed as described previously (Seo et al, 2009a;Kwak et al, 2013). To detect virus infection in the inoculated plants, RT-PCR was performed using a BBWV2-specific primer pair (59-CAGAGAAGTGGTTGG TCCCGTG-39 and 59-ATGGGAGGCTAGTGACCTACG-39) as described previously (Kwak et al, 2013).…”

“…Broad bean wilt virus2 (BBWV2), which belongs to the genus Fabavirus in the family Secoviridae, has a wide host range, including many economically important crops, such as pepper, cucumber (Cucumis sativus), broad bean (Vicia faba), and sesame (Sesamum indicum; Lisa and Boccardo, 1996;Kwak et al, 2013;Seo et al, 2017). The BBWV2 genome is composed of two singlestranded positive-sense RNA molecules, RNA1 and RNA2, which are approximately 5,960 and 3,600 nucleotides in length, respectively (Kwak et al, 2016).…”

The VP53 protein encoded by RNA2 of a fabavirus, broad bean wilt virus 2, is essential for viral systemic infection

“…In recent years, BBWV2 has emerged as a prevalent virus, displaying increasing incidence and severity in several horticultural crops in Korea, such as pepper, Chinese yam, and sesame 7 – 9 . Extensive studies have identified numerous strains and isolates of BBWV2 infecting various plant species, enabling the determination of their genome sequences 8 , 10 , 11 . Population genetic analyses conducted on these BBWV2 strains and isolates have provided insights into the high evolutionary plasticity of the BBWV2 genome, contributing to genetic and pathogenic diversification 8 , 12 .…”