Evolução molecular do gene metionina sintase em populações disjuntas de Carapichea ipecacuanha (Rubiaceae)

• Autor(a) principal: Benevenuto, Juliana
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4778
• topic: MetE; Ipeca; Diversidade; Diferenciação; Seleção natural; MetE; Ipecac; Diversity; Differentiation; Natural selection; CNPQ::CIENCIAS BIOLOGICAS::GENETICA::GENETICA VEGETAL

Cobalamin-independent methionine synthase (MetE) is a key enzyme for de novo synthesis of methionine in plants and it is also responsible for the regeneration of S-adenosylmethionine, which is a metabolite associated with the process of interaction with pathogens, plant growth and stresses response. In this study, 95 complete sequences of the gene for methionine synthase were obtained from 26 specimens of Carapichea ipecacuanha (species of Rubiaceae family, which is popularly known as ipecac) with aims to understand and model evolutionary events that occurred on MetE locus and on the specimens from three disjuncts ranges of occurrence of this species (Atlantic, Amazon and Central America ranges). Sequences of ITS and 5.8S from nrDNA and trnT-trnL spacers from cpDNA were also used for a multiloci population analysis. The sequenced region of MetE covered 3,890pb, where 2,298pb correspond to the coding region (composed of 11 exons) and 1,592pb to the noncoding region (comprising 10 introns and a portion of 3'UTR). In the entire sample were obtained 75 haplotypes and a nucleotide diversity of 0.00899. FST and AMOVA analyzes of MetE indicated no structure in three regions, opposite to detected for other loci analyzed here and in previous studies in which high divergence among the specimens from three ranges was observed. However, in the network haplotype was possible to observe the sympatric distribution of the haplotypes. Possibly, excess of tip haplotypes and the small number of mutational steps among neighboring haplotypes from the three ranges do not allow that the differentiation among these was significant. The Bayesian phylogenetic tree rooted by Carapichea lucida (outgroup) using the coding region sequences showed the formation of clades by geographic regions and provided evidence that sequences from "Atlantic" range is closer to the ancestral state of the gene MetE than sequences from others ranges. The heterogeneity of results for neutrality tests and for values of haplotype and nucleotide diversity at different loci suggests that these are evolving independently and also suggests that demographic events do not explain the pattern found. Thereby, tests for the presence of selection site-by-site were performed for the coding region of the gene MetE and protein alignment against others MetE from diferents plant species available in the Genbank was develop too. Four sites under positive selection were found, but the results show that negative selection (purifying selection) is the main force acting on the locus, favoring the conservation of protein structure and function in all gene copies from C. ipecacuanha.