RESUMO
RNA 2 and RNA 3 of lilac leaf chlorosis virus (LLCV) were sequenced and shown to be 2,762 nucleotides (nt) and 2,117 nts in length, respectively. RNA 2 encodes a putative 807-amino-acid (aa) RNA-dependent RNA polymerase associated protein with an estimated M (r) of 92.75 kDa. RNA 3 is bicistronic, with ORF1 encoding a putative movement protein (277 aa, M (r) 31.45 kDa) and ORF2 encoding the putative coat protein (221 aa, M (r) 24.37 kDa). The genome organization is similar to that typical for members of the genus Ilarvirus. Phylogenetic analyses indicate a close evolutionary relationship between LLCV, ApMV, and PNRSV.
Assuntos
Ilarvirus , Folhas de Planta/virologia , Proteínas do Movimento Viral em Plantas/genética , RNA Viral/genética , Análise de Sequência de DNA , Syringa/virologia , Proteínas Virais/genética , Ilarvirus/classificação , Ilarvirus/genética , Ilarvirus/isolamento & purificação , Dados de Sequência Molecular , Fases de Leitura Aberta/genética , Filogenia , Doenças das Plantas/virologia , Proteínas do Movimento Viral em Plantas/metabolismo , RNA Polimerase Dependente de RNA/química , RNA Polimerase Dependente de RNA/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Proteínas Virais/químicaRESUMO
Colombian datura virus (CDV) was first described in 1968 (3) and has since been reported in Europe (4), Japan (see 4 for additional references), and the United States (1,2). CDV is a member of the family Potyviridae with flexuous, filamentous nucleocapsids that can be transmitted by mechanical inoculation and grafting and is known to be vectored by the common aphid Myzus persicae. In the fall of 2007, five Brugmansia plants of unknown species from a Parks Board Collection in a Lower Mainland nursery, British Columbia, Canada, were found to be displaying symptoms typical of a viral infection: chlorotic flecking and mottling on leaves, leaf shrivel, and vein banding. Symptomatic leaves from these five plants were tested by ELISA (Immuno Strip Test, Agdia, Elkhart, IN) for several common viruses including Impatiens necrotic spot, Tobacco mosaic, Cucumber mosaic, and Tomato spotted wilt viruses and found to be negative for all. However, rub inoculations onto the herbaceous indicators Nicotiana occidentalis and N. benthamiana resulted in severe symptom formation including necrosis, wilting, shriveling, stunted growth, petiole and stem tip collapse, as well as collapse from the base of the plants, and plant death within 2 weeks after inoculation. A leaf dip assay of the original infected Brugmansia sample and infected N. benthamiana tissue revealed flexuous, potyvirus-like particles with the electron microscope (EM). On the basis of the Brugmansia leaf symptoms and the EM results, a possible infection with CDV was suspected. Primers CDV-3 and CDV-NIb5, specific to CDV (4), were used in a reverse transcription (RT)-PCR assay that amplified an approximate 1,600-bp fragment from the original Brugmansia sample and inoculated N. bentamiana and N. occidentalis plants. The amplified portion of the genome is the extreme 3' terminus and includes the 3' noncoding sequence, the viral coat protein gene, and part of the viral replicase gene. Fragments were cloned into pCR2.1-TOPO (Invitrogen, San Diego, CA) and two clones from each plant (total of six clones) were sequenced in both directions. Sequences of all clones were essentially identical, with only three nucleotide differences among the clones (GenBank Accession No. EU571230). BLASTn analysis revealed the highest match to several CDV isolates ranging from 98.7 to 99.5% nucleotide sequence identity. BLASTp analysis of the 451 amino acid viral polyprotein translation product gave a similarly high match with CDV isolates, with the highest match to a Hungarian isolate of CDV (GenBank Accession No. CAD26690) of 99.8% identity, or only one mismatch out of 451 amino acids. An additional group of 15 large symptomless Brugmansia plants, located approximately 6 m from the five symptomatic plants, were also tested by RT-PCR and found to be positive. These 15 plants were of a different but also unknown species of Brugmansia. In conclusion, analysis of symptomatic Brugmansia from a Canadian collection by transfer of disease to herbaceous indicators, EM, RT-PCR, and genomic sequence comparisons, are consistent with the detection and identification of the potyvirus Colombian datura virus. To our knowledge, this is the first report of this viral pathogen in Canada. References: (1) S. Adkins et al. Phytopathology (Abstr.) 95(suppl.):S2, 2005. (2) C. R. Fry et al. J. Phytopathol. 152:200, 2004. (3) R. P. Kahn and R. Bartels. Phytopathology 58:58, 1968. (4) J. Schubert et al. J. Phytopathol. 154:343, 2006.