Species diversity and genetic variability of bipartite begomoviruses in the new world

• Autor(a) principal: Xavier, César Augusto Diniz
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: https://locus.ufv.br//handle/123456789/27397
• topic: Begomovírus; Diversidade genética; Evolução; Filogeografia; Fitopatologia

The genus Begomovirus (family Geminiviridae) includes viruses with mono- and bipartite genome of circular, single-stranded DNA (ssDNA), transmitted by Bemisia tabaci to dicotyledonous plants. These viruses are divided into New World (NW) and Old World (OW) groups based on genomic organization and phylogenetic relationships. The begomoviruses constitute an important group of plant pathogens responsible for severe losses in several crops of economic importance, mainly tropical and subtropical regions. Begomoviruses evolve at high rates, compared to viruses with RNA genomes. Studies to determine the genetic structure and evolutionary dynamics of populations begomoviruses has been based solely on the DNA- A. This study aimed to: (i) carry out the molecular and biological characterization of two new begomoviruses isolated from the non-cultivated host Sida acuta; (ii) perform a comparative analysis of the genetic structure of NW begomoviruses based on the DNA-A and DNA-B components. For the first objective, total DNA was extracted from S. acuta samples collected in Viçosa, state of Minas Gerais in December 2011, and the viral genome was amplified by RCA, cloned and sequenced. Infectious clones were generated to perform the biological characterization. We identified two new species of OW-like begomoviruses present in the NW, named Sida yellow spot virus (SiYSV) and Sida golden yellow mosaic virus (SiGYMV). Moreover, both viruses have a highly divergent capsid protein gene. Interestingly, SiYSV was not transmitted by B. tabaci MEAM1. For the second objective we analyzed a total of 241 DNA-B sequences belonging to four begomovirus species (Bean golden mosaic virus, BGMV; Blainvillea yellow spot virus, BlYSV; Macroptilium yellow spot virus, MaYSV; Tomato severe rugose virus, ToSRV), obtained in this study, in addition to 239 DNA-A and 16 DNA-B sequences retrieved from GenBank. The DNA-B was more variable and more likely to recombine compared to the DNA-A. Analysis of the genetic structure of the viral populations based on either the DNA-A or the DNA-B indicated segregation based on geographical location. Together, our results indicate that while the DNA-A and DNA-B are co-evolving, they are under different selective pressures, with the DNA-B being more permissive to variation.