RESUMO
Recent phylogenetic studies on Sisyrinchium strongly suggest that species classified in section Hydastylus and section Viperella belong to a single group of plants in recent adaptive radiation (Clade IV). These species neither present clear morphological differentiation among them nor show clear identification using DNA barcode markers. Thus, the main goal of this study was to develop a set of polymorphic microsatellite markers compatible for representative species of both sections to ensure variability that could be revealed by SSR markers. Therefore, microsatellite primers were isolated and characterized for Sisyrinchium palmifolium and S. marchioides. In addition, transferability of the developed primers was tested in Iridoideae, primarily in closely related species of Sisyrinchium. Sixteen microsatellite loci were developed from enriched genomic libraries, of which ten were polymorphic. GST values indicated higher differentiation among subpopulations of S. palmifolium than those from S. marchioides. Major transferability was obtained using primers isolated from S. marchioides. All primers exhibited higher rates of cross-amplification for species belonging to Clade IV of Sisyrinchium, as well as to the genera Calydorea and Herbertia. These developed microsatellite markers can be used as an efficient tool for characterization of genetic variability in species belonging to Iridoideae, as well as for studies on population dynamics, genetic structure, and mating system in other Sisyrinchium species.
Assuntos
Iridaceae/genética , Repetições de Microssatélites/genética , Filogenia , Polimorfismo Genético , Especificidade da EspécieRESUMO
DNA barcoding aims to develop an efficient tool for species identification based on short and standardized DNA sequences. In this study, the DNA barcode paradigm was tested among the genera of the tribe Sisyrinchieae (Iridoideae). Sisyrinchium, with more than 77% of the species richness in the tribe, is a taxonomically complex genus. A total of 185 samples belonging to 98 species of Sisyrinchium, Olsynium, Orthrosanthus and Solenomelus were tested using matK, trnH-psbA and internal transcribed spacer (ITS). Candidate DNA barcodes were analysed either as single markers or in combination. Detection of a barcoding gap, similarity-based methods and tree-based analyses were used to assess the discrimination efficiency of DNA barcodes. The levels of species identification obtained from plastid barcodes were low and ranged from 17.35% to 20.41% for matK and 5.11% to 7.14% for trnH-psbA. The ITS provided better results with 30.61-38.78% of species identified. The analyses of the combined data sets did not result in a significant improvement in the discrimination rate. Among the tree-based methods, the best taxonomic resolution was obtained with Bayesian inference, particularly when the three data sets were combined. The study illustrates the difficulties for DNA barcoding to identify species in evolutionary complex lineages. Plastid markers are not recommended for barcoding Sisyrinchium due to the low discrimination power observed. ITS gave better results and may be used as a starting point for species identification.
Assuntos
Código de Barras de DNA Taxonômico/métodos , Iridaceae/classificação , Iridaceae/genética , DNA Espaçador Ribossômico/química , DNA Espaçador Ribossômico/genética , Genes de Plantas , Dados de Sequência Molecular , Plastídeos/genética , Análise de Sequência de DNARESUMO
BACKGROUND AND AIMS: The Neotropical tribe Trimezieae are taxonomically difficult. They are generally characterized by the absence of the features used to delimit their sister group Tigridieae. Delimiting the four genera that make up Trimezieae is also problematic. Previous family-level phylogenetic analyses have not examined the monophyly of the tribe or relationships within it. Reconstructing the phylogeny of Trimezieae will allow us to evaluate the status of the tribe and genera and to examine the suitability of characters traditionally used in their taxonomy. METHODS: Maximum parsimony and Bayesian phylogenetic analyses are presented for 37 species representing all four genera of Trimezieae. Analyses were based on nrITS sequences and a combined plastid dataset. Ancestral character state reconstructions were used to investigate the evolution of ten morphological characters previously considered taxonomically useful. KEY RESULTS: Analyses of nrITS and plastid datasets strongly support the monophyly of Trimezieae and recover four principal clades with varying levels of support; these clades do not correspond to the currently recognized genera. Relationships within the four clades are not consistently resolved, although the conflicting resolutions are not strongly supported in individual analyses. Ancestral character state reconstructions suggest considerable homoplasy, especially in the floral characters used to delimit Pseudotrimezia. CONCLUSIONS: The results strongly support recognition of Trimezieae as a tribe but suggest that both generic- and species-level taxonomy need revision. Further molecular analyses, with increased sampling of taxa and markers, are needed to support any revision. Such analyses will help determine the causes of discordance between the plastid and nuclear data and provide a framework for identifying potential morphological synapomorphies for infra-tribal groups. The results also suggest Trimezieae provide a promising model for evolutionary research.
Assuntos
Núcleo Celular/genética , Flores/anatomia & histologia , Iridaceae/classificação , Iridaceae/genética , Folhas de Planta/anatomia & histologia , Plastídeos/genética , Teorema de Bayes , DNA de Plantas , Evolução Molecular , Iridaceae/anatomia & histologia , Filogenia , Análise de Sequência de DNARESUMO
BACKGROUND AND AIMS: Sisyrinchium (Iridaceae: Iridoideae: Sisyrinchieae) is one of the largest, most widespread and most taxonomically complex genera in Iridaceae, with all species except one native to the American continent. Phylogenetic relationships within the genus were investigated and the evolution of oil-producing structures related to specialized oil-bee pollination examined. METHODS: Phylogenetic analyses based on eight molecular markers obtained from 101 Sisyrinchium accessions representing 85 species were conducted in the first extensive phylogenetic analysis of the genus. Total evidence analyses confirmed the monophyly of the genus and retrieved nine major clades weakly connected to the subdivisions previously recognized. The resulting phylogenetic hypothesis was used to reconstruct biogeographical patterns, and to trace the evolutionary origin of glandular trichomes present in the flowers of several species. KEY RESULTS AND CONCLUSIONS: Glandular trichomes evolved three times independently in the genus. In two cases, these glandular trichomes are oil-secreting, suggesting that the corresponding flowers might be pollinated by oil-bees. Biogeographical patterns indicate expansions from Central America and the northern Andes to the subandean ranges between Chile and Argentina and to the extended area of the Paraná river basin. The distribution of oil-flower species across the phylogenetic trees suggests that oil-producing trichomes may have played a key role in the diversification of the genus, a hypothesis that requires future testing.
Assuntos
Abelhas/fisiologia , Evolução Biológica , Flores/metabolismo , Iridaceae/classificação , Iridaceae/genética , Óleos de Plantas/metabolismo , Animais , Teorema de Bayes , DNA de Plantas/química , DNA de Plantas/genética , Genes de Plantas/genética , Geografia , Iridaceae/metabolismo , Funções Verossimilhança , Mitocôndrias/genética , América do Norte , Filogenia , Plastídeos/genética , Polinização , Alinhamento de Sequência , América do SulRESUMO
Eukaryotic chromosomes are organized into two large and distinct domains, euchromatin and heterochromatin, which are cytologically characterized by different degrees of chromatin compaction during interphase/prophase and by post-synthesis modifications of histones and DNA methylation. Typically, heterochromatin remains condensed during the entire cell cycle whereas euchromatin is decondensed at interphase. However, a fraction of the euchromatin can also remain condensed during interphase and appears as early condensing prophase chromatin. 5S and 45S rDNA sites and telomere DNA were used to characterize these regions in metaphase and interphase nuclei. We investigated the chromosomal distribution of modified histones and methylated DNA in the early and late condensing prophase chromatin of two species with clear differentiation between these domains. Both species, Costus spiralis and Eleutherine bulbosa, additionally have a small amount of classical heterochromatin detected by CMA/DAPI staining. The distribution of H4 acetylated at lysine 5 (H4K5ac), H3 phosphorylated at serine 10 (H3S10ph), H3 dimethylated at lysine 4 or 9 (H3K4me2, H3K9me2), and 5-methylcytosine was compared in metaphase, prophase, and interphase cells by immunostaining with specific antibodies. In both species, the late condensing prophase chromatin was highly enriched in H4K5ac and H3K4me2 whereas the early condensing chromatin was very poor in these marks. H3K9me2 was apparently uniformly distributed along the chromosomes whereas the early condensing chromatin was slightly enriched in 5-methylcytosine. Signals of H3S10ph were restricted to the pericentromeric region of all chromosomes. Notably, none of these marks distinguished classical heterochromatin from the early condensing euchromatin. It is suggested that the early condensing chromatin is an intermediate type between classical heterochromatin and euchromatin.
Assuntos
Cromatina/metabolismo , Costus , Metilação de DNA , DNA de Plantas/metabolismo , Histonas/metabolismo , Iridaceae , Costus/genética , Costus/metabolismo , Corantes Fluorescentes/metabolismo , Hibridização in Situ Fluorescente , Iridaceae/genética , Iridaceae/metabolismo , Coloração e RotulagemRESUMO
Tigridia pavonia (L.f.) DC. is one of the important phytogenetic resources of México. This species is used as ornamental, food and medicinal purposes. Despite its ornamental and economic potential, there is little information about the genetic variability. In this study, randomly amplified polymorphic DNA (RAPD) primers of 10, 15 and 20 bases were used to assess the level of genetic variation among nine botanical varieties of Tigridia pavonia collected in three localities within State of México. The total number fragments, polymorphic fragments, percentage of polymorphism and resolving power were greater for 15 base (55, 52, 94.5 and 5, respectively) and 20 base (47, 45, 95.7 and 3.8, respectively), in comparison with those obtained from 10 base primers (44, 41, 93.1 and 3.6, respectively).Results showed the major effectiveness of 15 and 20 bases RAPD primers in the genetic differentiation of varieties as compared to 10 bases RAPD primers. The dendrograms based on un-weighted pair group method arithmetic average (UPGMA) analysis of the 10, 15, 20 and the pooled (10, 15 and 20) bases RAPD data were consistent in the clustering varieties, grouping them in two main clusters.