Variability among the Isolates of Broad Bean Mottle Virus and Encapsidation of Host RNAs

Abstract

Broad bean mottle bromovirus infects legume plants and is transmissible by insects. Several broad bean mottle virus (BBMV) isolates have been identified, including one in England (isolate Ba) and five in the Mediterranean countries: Libya (LyV), Morocco (MV), Syria (SV), Sudan (TU) and Tunisia (TV). Previously, we analyzed the nucleotide sequence of the Ba RNA and here we report on and compare it with another five Mediterranean variants. The RNA segments in the latter ones were extensively homologous, with some SNPs, single nucleotide deletions and insertions, while the number of mutations was higher in isolate Ba. Both the 5′ and 3′ untranslated terminal regions (UTRs) among the corresponding RNAs are highly conserved, reflecting their functionality in virus replication. The AUG initiation codons are within suboptimal contexts, possibly to adjust/regulate translation. The proteins 1a, 2a, 3a and coat protein (CP) are almost identical among the five isolates, but in Ba they have more amino acid (aa) substitutions. Phylogenetic analysis revealed the isolates from Morocco and Syria clustering with the isolate from England, while the variants from Libya, Tunisia and Sudan created a different clade. The BBMV isolates encapsidate a high content of host (ribosomal and messenger) RNAs. Our studies present BBMV as a useful model for bromoviruses infecting legumes.

Characterization of Variant RNAs Encapsidated during Bromovirus Infection by High-Throughput Sequencing

“…RNA 359 (15), 906 (11), 950 (26), 1585 (27), 1586 (11), 1731 (15), 1801 (14) 359 (15), 1584 (25), 1585 (29), 1586 (16), 1801 (18) a Only events supported by ≥10 reads were counted.…”

“…The various kinds of BMV RNA recombinants described to date were analyzed in total RNA extracts from the infected tissue. We previously described that BMV and broad bean mottle virus (BBMV) virions could package the host cellular RNA sequences [24,25]. To find out if virions could package the recombinant variants, in this work we analyzed BMV or CCMV RNAs extracted from extensively purified viral preparations.…”