Análise comparativa do genoma de dois isolados de Cowpea aphid-borne mosaic virus (CABMV) obtidos de diferentes hospedeiros

• Autor(a) principal: Barros, Danielle Ribeiro de
• Data de Publicação: 2007
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1016
• topic: Cowpea aphid-borne mosaic virus; Potyvirus; Virus de planta; Cowpea aphid-borne mosaic virus; Potyvirus; Plant virus; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA

In Brazil and in other countries where passionfruit is grown, the viral disease known as passionfruit woodiness is a limiting factor for production. For many years this disease was associated with a single potyvirus, Passion fruit woodiness virus (PWV). However, studies conducted over the last 20 years demonstrated that two additional potyviruses, Cowpea aphidborne mosaic virus (CABMV) and East Asian Passiflora virus (EAPV) can also cause passionfruit woodiness. Plants infected by either one of these three viruses display mosaic in the leaves and woodiness of the pericarp of the fruit. In Brazil, molecular analysis has shown that several potyvirus isolates previously classified as PWV based on biological and serological properties are actually CABMV isolates. These isolates are capable of infecting legume crops such as common bean (Phaseolus vulgaris) and cowpea (Vigna unguiculata). To this date, only one CABMV isolate (CABMV- Zimbabwe, obtained from cowpea) has been completely sequenced. For some Brazilian isolates, the capsid protein (CP) coding region and the 3 -untranslated region have been sequenced. Sequence analysis did not indicate any features that could be correlated with biological differences among the isolates. The objective of this work was to determined the complete genomic sequence of two CABMV isolates from Brazil, one obtained from passionfruit with woodiness symptoms (isolate MGAvr, which also infects bean and cowpea), and one obtained from peanut (isolate BR1, which also infects bean and cowpea, but does not infect passionfruit). Both isolates were maintained in cowpea plants of the cultivar Pitiúba. Viral RNA was purified from concentrated virions and used as a template for cDNA synthesis, which was then used as a template for long range PCR using a high fidelity DNA polymerase and different combinations of degenerate and specific primers. The nucleotide sequences of isolates BR1 and MG-Avr are 95% identical and display 87 and 86% identity with CABMV-Z, respectively. Both isolates have the typical potyvirus genome features, including the potential to encode a polyprotein which can generate 8 to 10 putative viral proteins by autoproteolysis. Among these putative viral proteins, P3 and VPg are the most conserved between the two isolates, with 99% amino acid sequence identity, and the CP is the least conserved, with 85% identity. Phylogenetic analysis indicates that the two Brazilian isolates group with CABMV-Z in the legume-infecting species cluster, and in the Bean common mosaic virus (BCMV) subgroup. Mutagenesis studies and phenotypic analysis could identify genomic regions or amino acids involved in the biological differences between the two isolates.