The cataloging of the vascular plants of the Americas has a centuries-long history, but it is only in recent decades that an overview of the entire flora has become possible. We present an integrated ...assessment of all known native species of vascular plants in the Americas. Twelve regional and national checklists, prepared over the past 25 years and including two large ongoing flora projects, were merged into a single list. Our publicly searchable checklist includes 124,993 species, 6227 genera, and 355 families, which correspond to 33% of the 383,671 vascular plant species known worldwide. In the past 25 years, the rate at which new species descriptions are added has averaged 744 annually for the Americas, and we can expect the total to reach about 150,000.
Dating the Species Network Mccann, Jamie; Jang, Tae-Soo; Macas, JiřI ...
Systematic biology,
11/2018, Letnik:
67, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Allopolyploidy has played an important role in the evolution of the flowering plants. Genome mergers are often accompanied by significant and rapid alterations of genome size and structure via ...chromosomal rearrangements and altered dynamics of tandem and dispersed repetitive DNA families. Recent developments in sequencing technologies and bioinformatic methods allow for a comprehensive investigation of the repetitive component of plant genomes. Interpretation of evolutionary dynamics following allopolyploidization requires both the knowledge of parentage and the age of origin of an allopolyploid. Whereas parentage is typically inferred from cytogenetic and phylogenetic data, age inference is hampered by the reticulate nature of the phylogenetic relationships. Treating subgenomes of allopolyploids as if they belonged to different species (i.e., no recombination among subgenomes) and applying cross-bracing (i.e., putting a constraint on the age difference of nodes pertaining to the same event), we can infer the age of allopolyploids within the framework of the multispecies coalescent within BEAST2. Together with a comprehensive characterization of the repetitive DNA fraction using the RepeatExplorer pipeline, we apply the dating approach in a group of closely related allopolyploids and their progenitor species in the plant genus Melampodium (Asteraceae). We dated the origin of both the allotetraploid, Melampodium strigosum, and its two allohexaploid derivatives, Melampodium pringlei and Melampodium sericeum, which share both parentage and the direction of the cross, to the Pleistocene (<1.4 Ma). Thus, Pleistocene climatic fluctuations may have triggered formation of allopolyploids possibly in short intervals, contributing to difficulties in inferring the precise temporal order of allopolyploid species divergence of M. sericeum and M. pringlei. The relatively recent origin of the allopolyploids likely played a role in the near-absence of major changes in the repetitive fraction of the polyploids’ genomes. The repetitive elements most affected by the postpolyploidization changes represented retrotransposons of the Ty1-copia lineage Maximus and, to a lesser extent, also Athila elements of Ty3-gypsy family.
Wet chemical synthesis of hydroxyapatite (HAp) nanostructures was carried out with different solution pH values (9, 10 and 11) and sintering temperatures (300°C, 500°C, 700°C and 900°C). The effects ...of pH and sintering temperature on the structural and morphological properties of nanocrystalline HAp powders were presented. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis were performed to obtain the crystalline structure, chemical composition, morphology and particle size of the HAp powders. The TEM analysis is used in order to observe the rod- and flake-like HAp structures. XRD confirms the presence of both HAp hexagonal and monetite phases, although the monetite phase was less abundant in the resultant powders. Increase in pH reduced the monetite phase and enhanced Ca/P ratio from 1.7 to 1.83. Additionally, an increment in sintering temperature increased the crystallite size from 20 to 56 nm. The SEM analysis revealed the formation of semi-spherical and flake-like HAp structures with preferential flake morphology. An increase in pH and sintering temperature resulted in the growth and coalescence of crystals resulting in a porous capsular morphology. The FTIR analysis confirmed the reduction of carbonate stretching modes with an increase in pH and H–O–H antisymmetric stretching mode is eliminated for powders sintered at 900°C confirming the formation of stable and porous HAp powders.
The application of nano-biotechnology to crop-science/agriculture (‘nanoagriculture’) is a recent development. While carbon nanotubes (CNTs) have been shown to dramatically improve germination of ...some comestible plants, deficiencies in consistency of behavior and reproducibility arise, partially from the variability of the CNTs used. In this work, factory-synthesized multi-walled-CNTs (MWCNTs) of quality-controlled specifications were seen to enhance the germinative growth of maize seedlings at low concentrations but depress it at higher concentrations. Growth enhancement principally arose through improved water delivery by the MWCNT. Polarized EDXRF spectrometry showed that MWCNTs affect mineral nutrient supply to the seedling through the action of the mutually opposing forces of inflow with water and retention in the medium by the ion-CNT transient-dipole interaction. The effect varied with ion type and MWCNT concentration. The differences of the Fe tissue concentrations when relatively high equimolar Fe
2+
or Fe
3+
was introduced, implied that the ion-CNT interaction might induce redox changes to the ion. The tissue Ca
2+
concentration manifested as the antipode of the Fe
2+
concentration indicating a possible cationic exchange in the cell wall matrix. SEM images showed that MWCNTs perforated the black-layer seed-coat that could explain the enhanced water delivery. The absence of perforations with the introduction of FeCl
2
/FeCl
3
reinforces the idea of the modification of MWCNT functionality by the ion-CNT interaction. Overall, in normal media, low dose MWCNTs were seen to be beneficial, improving water absorption, plant biomass and the concentrations of the essential Ca, Fe nutrients, opening a potential for possible future commercial agricultural applications.
Polyploidy, an important factor in eukaryotic evolution, is especially abundant in angiosperms, where it often acts in concert with hybridization to produce allopolyploids. The application of ...molecular phylogenetic techniques has identified the origins of numerous allopolyploids, but little is known on genomic and chromosomal consequences of allopolyploidization, despite their important role in conferring divergence of allopolyploids from their parental species. Here, using several plastid and nuclear sequence markers, we clarify the origin of tetra-and hexaploids in a group of American daisies, allowing characterization of genome dynamics in polyploids compared to their diploid ancestors. All polyploid species are allopolyploids. Among the four diploid gene pools, the propensity for allopolyploidization is unevenly distributed phylogenetically with a few species apparently more prone to participate, but the underlying causes remain unclear. Polyploid genomes are characterized by differential loss of ribosomal DNA loci (5S and 35S rDNA), known hotspots of chromosomal evolution, but show genome size additivity, suggesting limited changes beyond those affecting rDNA loci or the presence of processes counterbalancing genome reduction. Patterns of rDNA sequence conversion and provenance of the lost loci are highly idiosyncratic and differ even between allopolyploids of identical parentage, indicating that allopolyploids deriving from the same lower-ploid parental species can follow different evolutionary trajectories.
Apiaries must be located in areas with abundant flora as they are the nutritional base for
. Asteraceae is one of the most diverse plant families in Mexico and several of its species are of interest ...for beekeepers. The objective of this study was to determine the best sites for the placement of apiaries with the use of ecological niche models (ENM) of some Asteraceae species important for bees in two basins of the state of Michoacán, Mexico. ENM for thirty species were obtained through records of their presence, twenty abiotic variables and one biotic variable, and a map of species richness was made to determine which sites would be environmentally appropriate for apiaries. The models were statistically evaluated using the AUC_Maxent, partial_ROC and the binomial tests and were verified in the field. The first two tests’ models had values of 0.70 to 1 and the binomial test’s models had values of 1. The map showed six suitable areas with the greatest richness of species. The corroboration in the field proved ENM effective by finding twenty-two of the thirty modeled species inside the predicted areas. Our results support that ENM are a good strategy to predict the ideal habitat for species important for beekeeping, and thus determine the best places to establish apiaries in the region.
Introduction
Previous studies report the isolation mainly of terthiophene derivatives and flavonoids from Dyssodia species. Terthiophenes are known as photosensitizers by their capacity to generate ...singlet oxygen (1O2), and flavonoid antioxidant activity is recognized. These opposite properties could represent interesting options in photodynamic therapy.
Objective
To determine the antioxidant and photosensitizer activities of extracts and isolates of Dyssodia pinnata by electron paramagnetic resonance (EPR).
Methodology
Extracts and isolates were evaluated as antioxidants by the interactions with copper ion (Cu2+) observed in EPR, and by the 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH) and the thiobarbituric reactive substances (TBARS) methods. Their abilities as 1O2 producers were also estimated by EPR.
Results
Terthiophenes were obtained from hexane (DPH) and acetone (DPA) extracts, and flavonoids from DPA and methanol (DPM) extracts. The interaction with Cu2+ of extracts and isolated compounds of Dyssodia pinnata showed two effects in EPR: reduction and chelation; flavonoids exhibited both effects, while terthiophenes showed only reduction. DPA, DPM, and flavonoids were active in DPPH and TBARS assays. Quercetagetin‐7‐O‐β‐glucoside showed the highest antioxidant and chelating activities, 3‐glycosidated flavonoids were less active. Upon irradiation extracts and terthiophenes induced 1O2 formation.
Conclusion
Flavonoid reducing activity on Cu2+ and free radical scavenging capacity were related to the number of hydroxy groups and to the conjugation between the B and C rings. All tested flavonols showed a major complex with Cu2+, with the most probable site of chelation between the 5‐hydroxy and 4‐oxo groups. Extracts and terthiophene derivatives showed photosensitizer activity. Thus, EPR is useful to evaluate free radical scavenging and pro‐oxidant properties.
The phytochemical study of Dyssodia pinnata led to the isolation of terthiophenes and flavonoids. The antioxidant activity of extracts and isolates was evaluated by the reductive and chelating effects on Cu+2 observed in EPR, and by the 2,2‐diphenyl‐1‐picrylhydrazyl radical and the thiobarbituric reactive substances methods. Their abilities as singlet oxygen producers were estimated by EPR. Results show that EPR could be a useful technique to determine the potential of natural products to prevent oxidative damage, and to evaluate pro‐oxidant properties.
The present work studies the effect of Mn doping on the crystalline structure of the Hap synthesized by the hydrothermal method at 200 °C for 24 h, from Ca(OH)
2
and (NH
4
)
2
HPO
4
, incorporating ...MnCl
2
to 0.1, 0.5, 1.0, 1.5 and 2.0 %wt of Mn concentrations. Samples were characterized by the X-Ray Diffraction technique, which revealed the diffraction peaks that corresponded to the hexagonal and monoclinic phase of the Hap; it was observed that the average size of crystallite decreased from 23.67 to 22.69 nm as the concentration of Mn increased. TEM shows that in all samples, there are two distributions of particle sizes; one corresponds to nanorods with several tens of nanometers in length, and the other in which the diameter and length are very close. FTIR analysis revealed absorption bands corresponding to the PO
4
−3
and OH
−
groups characteristic of the Hap. It was possible to establish a substitution mechanism between the Mn and the ions of Ca
+2
of the Hap. From the Alamar blue test, a cell viability of 86.88% ± 5 corresponding to the sample of Hap at 1.5 %wt Mn was obtained, considered non-cytotoxic according to ISO 10993-5. It also evaluated and demonstrated the good osteoinductive properties of the materials, which were verified by histology and immunofluorescence expression of osteogenic markers. Adhesion, viability, biocompatibility and osteoinductive properties, make these materials candidates for future applications in bone tissue engineering with likely uses in regenerative medicine.
Graphical Abstract
Plant genomes vary greatly in composition and size mainly due to the diversity of repetitive DNAs and the inherent propensity for their amplification and removal from the host genome. Most studies ...addressing repeatome dynamics focus on model organisms, whereas few provide comprehensive investigations across the genomes of related taxa. Herein, we analyze the evolution of repeats of the 13 species in
sect.
, representing all but two of its diploid taxa, in a phylogenetic context. The investigated genomes range in size from 0.49 to 2.27 pg/1C (ca. 4.5-fold variation), despite having the same base chromosome number (
= 10) and very strong phylogenetic affinities. Phylogenetic analysis performed in BEAST and ancestral genome size reconstruction revealed mixed patterns of genome size increases and decreases across the group. High-throughput genome skimming and the RepeatExplorer pipeline were utilized to determine the repeat families responsible for the differences in observed genome sizes. Patterns of repeat evolution were found to be highly correlated with phylogenetic position, namely taxonomic series circumscription. Major differences found were in the abundances of the SIRE (
), Athila (
), and
(DNA transposon) lineages. Additionally, several satellite DNA families were found to be highly group-specific, although their overall contribution to genome size variation was relatively small. Evolutionary changes in repetitive DNA composition and genome size were complex, with independent patterns of genome up- and downsizing throughout the evolution of the analyzed diploids. A model-based analysis of genome size and repetitive DNA composition revealed evidence for strong phylogenetic signal and differential evolutionary rates of major lineages of repeats in the diploid genomes.
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