Molecular characterization of two genotypes of a new polerovirus infecting brassicas in China

Abstract

The genomic RNA sequences of two genotypes of a brassica-infecting polerovirus from China were determined. Sequence analysis revealed that the virus was closely related to but significantly different from turnip yellows virus (TuYV). This virus and other poleroviruses, including TuYV, had less than 90% amino acid sequence identity in all gene products except the coat protein. Based on the molecular criterion (>10% amino acid sequence difference) for species demarcation in the genus Polerovirus, the virus represents a distinct species for which the name Brassica yellows virus (BrYV) is proposed. Interestingly, there were two genotypes of BrYV, which mainly differed in the 5'-terminal half of the genome.

Simultaneous detection and differentiation of three genotypes of Brassica yellows virus by multiplex reverse transcription-polymerase chain reaction

“…Four primers BrYA484F/ BrYB88F/ BrYC257F/ BrY761R were newly designed in the conserved regions within ORF0 of each genotype to allow for mRT-PCR. The three genotypes of BrYV were closely related to, but distinct from, TuYV in terms of P0, P3, P4 and P5 gene sequences [1, 4]. In order to detect TuYV at the same time, a pair of primers TuY4959F/TuY5163R in the conserved regions within ORF5 were designed (Table 1).…”

“…Brassica yellows virus (BrYV) is an aphid-transmitted and phloem-limited virus as other poleroviruses do (unpublished data). BrYV is distributed widely in mainland China, as well as in South Korea and Japan [1–3]. BrYV can infect nine cruciferous plant species including cabbage ( Brassica oleracea var.…”

“…oleifera ). It can cause yellowing and leaf malformation or mottling symptoms on cruciferous crops [1, 2]. …”

“…BrYV has a single-stranded, positive-sense RNA genome containing six open reading frames (ORFs), and the three genotypes of BrYV have greater divergence in ORFs 0, 1 and 2 than in ORFs 3, 4 and 5 [1, 4]. For convenience of the virus research, the full-length infectious cDNA clones of the three genotypes were constructed under control of the cauliflower mosaic virus 35S promoter.…”

“…RT-PCR with universal primers (PoconF/ PococpR) was used for the amplification of a 1.4 kb band for poleroviruses [1, 6]. As to BrYV, it can be further determined by western blot and northern blot detection [5].…”