Contrastando padrões de recombinação em isolados de Potyvírus obtidos de plantas monocotiledôneas e dicotiledôneas

Abstract

Viruses are able to induce diseases in many economically important plant species causing severe losses in agriculture. Potyviruses (genus Potyvirus, family Potyviridae) account for about 90% of the species known in the family. They possess RNA as genetic material and their populations show a high degree of genetic variability. The main mechanisms that act on the evolution of viruses are mutation and recombination. Mutations may occur spontaneously due to misincorporation of nucleotides during viral replication. Recombination consists in the exchange of genetic material fragments between distinct viruses during mixed infections. The high frequency of recombination is responsible for the emergence of new genetic characteristics in the viruses, as the ability to infect new hosts and to overcome the host genetic resistance. In order to better understand the factors involved in the high genetic variability of these virus populations, recombination events were detected using bioinformatics tools based on complete genomic sequences of potyviruses. Two data sets were analyzed: the first one composed of potyvirus isolates that infect predominantly monocotyledonous plants and the second one composed of isolates that typically infect dicotyledonous plants. The complete genomes were obtained from GenBank by using the Taxonomy browser and were subsequently analyzed into two programs, MEGA (Molecular Evolutionary Genetics Analysis) and RDP (Recombination Detection Program) and the results were interpreted from breakpoint distribution plots. The results of this study indicate that the recombination occurs frequently in the viral isolates analyzed and the breakpoint distribution patterns are different between potyviruses that predominantly infect monocotyledonous or dicotyledonous plants. While the genomes of monocot-infecting potyviruses show a higher frequency of recombination in the 3' portion, the genomes of dicot-infecting potyviruses are more prone to recombination in the 5' portion.