Variabilidade e estrutura genética de populações do begomovírus Cnidoscolus mosaic leaf deformation vírus (CnMLDV) infectando Cnidoscolus urens (L.) Arthur (Cansanção)

Abstract

Viruses in the Family Geminiviridae have circular single-stranded DNA genome that is encapsidated into twinned quasi-icosahedral particles and are divided into four genera (Becurtovirus, Begomovirus, Curtovirus, Eragrovirus, Mastrevirus, Topocuvirus e Turncurtovirus) based on the type of insect vector, genome organization, host range and phylogenetic relationship. Begomovirus are transmitted by whiteflies within the Bemisia tabaci cryptic species complex and cause great losses in economically important crops worldwide. Besides being able to infect crop plants begomoviruses also infect weed/wild plants which serve as viral reservoir. Aiming to evaluate the genetic variability and population structure of begomoviruses infecting the non-cultivated host Cnidoscolus urens (L.) Arthur, leaf samples showing indicative symptoms of begomoviral infection were collected in different locations within Alagoas State in the years 2015 and 2016. Total DNA was extracted from each sample and used as template for rolling circle amplification (RCA) followed by cloning and sequencing. Pairwise sequence comparisons analysis of DNA-A showed that all isolates belong to a single species: Cnidoscolus mosaic leaf deformation virus (CnMLDV). Phylogenetic and population structure analyses showed that CnMLDV isolates are separated in two subpopulations (North and South) which have high nucleotide variability values. Recombination and network evolution analyses showed strong evidence of recombination events occurring between CnMLDV isolates. Finally, strong negative selection pressure acting upon CP and Rep genes of CnMLDV was detected. Taken together these results show that the high genetic variability observed in CnMLDV isolates is directly related to frequent recombination events occurring along the virus genome and that strong purifying selection acts in a way to maintain the viral proteins amino acid sequences. Furthermore, mutation was determined as one of the main factors acting in the diversification of CnMLDV isolates.