Estudo in silico baseado em sequências de DNA plastidial de espécies de Malvaceae: filogenia e DNA barcode

Abstract

The family Malvaceae, belonging to the order Malvales, has approximately 4300 species distributed in about 300 genera and nine subfamilies. This family is known mainly for presenting species of great economic importance, which includes food species such as cocoa (Theobroma cacao) and okra (Abelmoschus esculentus), ornamental species such as hibiscus (Hibiscus), baobabs (Adansonia) and paineira. (Ceiba), species that are sources of natural fibers such as cotton (Gossypium hirsutum) and species that provide wood such as balsa (Ochroma). The Malvaceae family is cosmopolitan and its species are distributed practically all over the world, with the exception of very cold regions. The classification of this family is problematic and unresolved relationships between the subfamilies were evidenced. The objective of this work was to perform comparative genomics, divergence time and phylogeny analyzes of the Malvaceae family, using plastid markers, as well as to indicate sequences for use as barcode DNA in species of the genus Gossypium. For this, plastid genomes of 102 species of Malvaceae and related species (outgroup) from a database were used. Through the VISTA chart, it was possible to show high conservation and similarity between the plastomes of Malvaceae. The sequences of the selected genes (matK, rbcL, atpB and ndhF) were used to obtain the phylogenetic tree using the maximum likelihood method, with 1000 bootstrap, which resulted in a well-supported monophyletic tree. Malvaceae was divided into two main clades (Malvadendrina and Byttneriina), with high support. In Malvadendrina, the Malvatheca clade (Malvoideae and Bombacoideae) showed a low support value, but this relationship is corroborated by the presence of botanical characteristics such as the presence of monothecal anthers and the absence of androgynophore. This clade formed a well-supported sister group to the subfamilies Dombeyoideae, Brownlowioideae, Helicteroideae, Tiliodeae and Sterculioideae. But relationships between Brownlowioideae, Helicteroideae, Tiliodeae and Sterculioideae have not been resolved. The Byttneriina clade (Grewioideae and Byttnerioideae) was strongly supported. According to the analysis of the divergence time, it was evidenced that the subfamilies of Malvaceae diverged between the Paleocene and Eocene periods. For the analysis of candidate regions for barcode DNA, ten gene regions (accD, atpA, atpB, matK, ndhF, petD, psbA, rbcL, rpoA and rpoC2) and an inter-gene region (trnH-psbA) were used. The analyzes of the 11 loci showed a tendency for the grouping of Gossypium species by type of genome and geographic origin, but it was not possible to differentiate at the level of subspecies and/or variety.