The common or brinjal eggplant (Solanum melongena L.) belongs to the Leptostemonum Clade (the "spiny" solanums) of the species-rich genus Solanum (Solanaceae). Unlike most of the genus, the eggplant ...and its relatives are from the Old World; most eggplant wild relatives are from Africa. An informal system for naming eggplant wild relatives largely based on crossing and other biosystematics data has been in use for approximately a decade. This system recognises several forms of two broadly conceived species, S. incanum L. and S. melongena. Recent morphological and molecular work has shown that species-level differences exist between these entities, and a new species-level nomenclature has been identified as necessary for plant breeders and for the maintenance of accurately named germplasm.
We examined herbarium specimens from throughout the wild species ranges as part of a larger revision of the spiny solanums of Africa. Based on these morphological and molecular studies, we delimited species in the group to which the common eggplant belongs and constructed identification keys for the group. We also examined the monophyly of the group considered as the eggplant relatives by previous authors.
WE RECOGNISE TEN SPECIES IN THIS GROUP: S. aureitomentosum Bitter, S. campylacanthum A.Rich., S. cerasiferum Dunal, S. incanum L., S. insanum L., S. lichtensteinii Willd., S. linnaeanum Hepper & P.-M.L.Jaeger, S. melongena L., S. rigidum Lam. and S. umtuma Voronts. & S.Knapp. We review the history of naming and provide keys and character lists for all species. Ploidy level differences have not been investigated in the eggplant wild relatives; we identify this as a priority for improvement of crop wild relative use in breeding. The application of species-level names to these entities will help focus new collecting efforts for brinjal eggplant improvement and help facilitate information exchange.
•We developed a novel method for isolation of exosomes by sequential filtration.•Exosome isolates from biofluids via the method exhibit uniform size and morphology.•Exosome isolates from biofluids ...via the method express typical exosomal biomarkers.
Early and minimally invasive detection of malignant events or other pathologies is of utmost importance in the pursuit of improved patient care and outcomes. Recent evidence indicates that exosomes and extracellular vesicles in serum and body fluids can contain nucleic acid, protein, and other biomarkers. Accordingly, there is great interest in applying these clinically as prognostic, predictive, pharmacodynamic, and early detection indicators. Nevertheless, existing exosome isolation methods can be time-consuming, require specialized equipment, and/or present other inefficiencies regarding purity, reproducibility and assay cost. We have developed a straightforward, three-step protocol for exosome isolation of cell culture supernatants or large volumes of biofluid based on sequential steps of dead-end pre-filtration, tangential flow filtration (TFF), and low-pressure track-etched membrane filtration that we introduce here. Our approach yields exosome preparations of high purity and defined size distribution and facilitates depletion of free protein and other low-molecular-weight species, extracellular vesicles larger than 100nm, and cell debris. Samples of exosomes prepared using the approach were verified morphologically by nanoparticle tracking analysis and electron microscopy, and mass spectrometry analyses confirmed the presence of previously reported exosome-associated proteins. In addition to being easy-to-implement, sequential filtration yields exosomes of high purity and, importantly, functional integrity as a result of the relatively low-magnitude manipulation forces employed during isolation. This answers an unmet need for preparation of minimally manipulated exosomes for investigations into exosome function and basic biology. Further, the strategy is amenable to translation for clinical exosome isolations because of its speed, automatability, scalability, and specificity for isolating exosomes from complex biological samples.
Most people can name a mammal or bird that has become extinct in recent centuries, but few can name a recently extinct plant. We present a comprehensive, global analysis of modern extinction in ...plants. Almost 600 species have become extinct, at a higher rate than background extinction, but almost as many have been erroneously declared extinct and then been rediscovered. Reports of extinction on islands, in the tropics and of shrubs, trees or species with narrow ranges are least likely to be refuted by rediscovery. Plant extinctions endanger other organisms, ecosystems and human well-being, and must be understood for effective conservation planning.
Protein-rich clusters of steady submicron size and narrow size distribution exist in protein solutions in apparent violation of the classical laws of phase equilibrium. Even though they contain a ...minor fraction of the total protein, evidence suggests that they may serve as essential precursors for the nucleation of ordered solids such as crystals, sickle-cell hemoglobin polymers, and amyloid fibrils. The cluster formation mechanism remains elusive. We use the highly basic protein lysozyme at nearly neutral and lower pH as a model and explore the response of the cluster population to the electrostatic forces, which govern numerous biophysical phenomena, including crystallization and fibrillization. We tune the strength of intermolecular electrostatic forces by varying the solution ionic strength I and pH and find that despite the weaker repulsion at higher I and pH, the cluster size remains constant. Cluster responses to the presence of urea and ethanol demonstrate that cluster formation is controlled by hydrophobic interactions between the peptide backbones, exposed to the solvent after partial protein unfolding that may lead to transient protein oligomers. These findings reveal that the mechanism of the mesoscopic clusters is fundamentally different from those underlying the two main classes of ordered protein solid phases, crystals and amyloid fibrils, and partial unfolding of the protein chain may play a significant role.
The ecology of Madagascar's grasslands is under-investigated and the dearth of ecological understanding of how disturbance by fire and grazing shapes these grasslands stems from a perception that ...disturbance shaped Malagasy grasslands only after human arrival. However, worldwide, fire and grazing shape tropical grasslands over ecological and evolutionary timescales, and it is curious Madagascar should be a global anomaly. We examined the functional and community ecology of Madagascar's grasslands across 71 communities in the Central Highlands. Combining multivariate abundance models of community composition and clustering of grass functional traits, we identified distinct grass assemblages each shaped by fire or grazing. The fire-maintained assemblage is primarily composed of tall caespitose species with narrow leaves and low bulk density. By contrast, the grazer-maintained assemblage is characterized by mat-forming, high bulk density grasses with wide leaves. Within each assemblage, levels of endemism, diversity and grass ages support these as ancient assemblages. Grazer-dependent grasses can only have co-evolved with a now-extinct megafauna. Ironically, the human introduction of cattle probably introduced a megafaunal substitute facilitating modern day persistence of a grazer-maintained grass assemblage in an otherwise defaunated landscape, where these landscapes now support the livelihoods of millions of people.
Aim Successful colonization after long-distance dispersal (LDD) depends on the availability of suitable habitats and competitive ability. In this study, we address the hypothesis that two widely ...distributed sister grass lineages (broad- and fine-leaved Loliinae; hereafter BL and FL) that differ in their habitat requirements and competitive ability also differ in their biogeographic history, with particular reference to LDD. Location Global. Methods We reconstructed a comprehensive phylogeny of Loliinae, based on nuclear and plastid markers and estimated divergence times using fossil calibrations. Biogeographical events were estimated using analysis of range evolution, comparing different models. Numbers and rates of dispersals were estimated for BL and FL using stochastic mapping with best-performing and baseline biogeographical models, and examined for correlation with distance, disjunction type, and phenotypic syndrome. Results The most recent common ancestor of Loliinae likely split at the Oligocene-Miocene transition (22.50 ± 3.95 Ma), pre-dating previous estimates, whereas the ancestors of the BL and FL Loliinae likely began to diversify in the Early Miocene (18.91 ± 4.15 and 17.50 ± 3.50 Ma, respectively). A model of range evolution integrating founder events and scaling of dispersal by shortest distance between areas performed best amongst a set of alternative models and recovered a mean of 83 dispersal events in Loliinae. Overall dispersal rates were significantly higher in BL than in FL. Per-route dispersal rates showed a significant negative exponential relationship to shortest distance but were not affected by phenotypic syndrome or disjunction type. Main conclusions Loliinae originated in the Northern Hemisphere and evolved through recurrent LDDs. Higher competitive ability, potentially related to the broad-leaved syndrome (i.e. tall strong-rhizomatous plants, long-living individuals, occupancy of more stable habitats), may explain higher observed dispersal rates in BL compared with FL Loliinae. However, the dominant factor impacting dispersal in both BL and FL Loliinae is the distance between suitable areas.
C ₄ photosynthesis is a series of anatomical and biochemical modifications to the typical C ₃ pathway that increases the productivity of plants in warm, sunny, and dry conditions. Despite its ...complexity, it evolved more than 62 times independently in flowering plants. However, C ₄ origins are absent from most plant lineages and clustered in others, suggesting that some characteristics increase C ₄ evolvability in certain phylogenetic groups. The C ₄ trait has evolved 22–24 times in grasses, and all origins occurred within the PACMAD clade, whereas the similarly sized BEP clade contains only C ₃ taxa. Here, multiple foliar anatomy traits of 157 species from both BEP and PACMAD clades are quantified and analyzed in a phylogenetic framework. Statistical modeling indicates that C ₄ evolvability strongly increases when the proportion of vascular bundle sheath (BS) tissue is higher than 15%, which results from a combination of short distance between BS and large BS cells. A reduction in the distance between BS occurred before the split of the BEP and PACMAD clades, but a decrease in BS cell size later occurred in BEP taxa. Therefore, when environmental changes promoted C ₄ evolution, suitable anatomy was present only in members of the PACMAD clade, explaining the clustering of C ₄ origins in this lineage. These results show that key alterations of foliar anatomy occurring in a C ₃ context and preceding the emergence of the C ₄ syndrome by millions of years facilitated the repeated evolution of one of the most successful physiological innovations in angiosperm history.
The two-step mechanism of nucleation of crystals in solutions posits that the formation of crystal nuclei occurs within structures of extended lifetimes, in which the nucleating solute is at high ...concentration. The validity of this mechanism has been demonstrated for proteins, small-molecule organic and inorganic materials, colloids, and polymers. Due to large molecule sizes, proteins are an ideal system to study the details of this nucleation pathway, in particular the formation mechanisms of the nucleation precursors and the associated physico-chemical rules. The precursors of protein crystal nuclei are protein-rich clusters of sizes ∼100 nm that contain 10,000-100,000 molecules and occupy less than 10(-3) of the total solution volume. Here we demonstrate, using oblique illumination microscopy, the liquid nature of the clusters of the protein lysozyme and reveal their inhomogeneous structure. We test a hypothesis put forth by theory that clusters primarily consist of transient protein oligomers. For this, we explore how varying the strength of the Coulomb interaction affects the cluster characteristics. We find that the cluster's size is insensitive to variations of pH and ionic strength. In contrast, the addition of urea, a chaotropic agent that leads to protein unfolding, strongly decreases the cluster size. Shear stress, a known protein denaturant, induced by bubbling of the solutions with an inert gas, elicits a similar response. These observations support partial protein unfolding, followed by dimerization, as the mechanism of cluster formation. The amide hydrogen-deuterium exchange, monitored by nuclear magnetic resonance, highlights that lysozyme conformational flexibility is a condition for the formation of the protein-rich clusters and facilitates the nucleation of protein crystals.
Aim
Grasses (Poaceae) are found in all major habitats of Madagascar and have a particular importance in C4 grasslands, whose origins are controversial. We aimed to estimate the number, age and ...origins of endemic grass lineages in the Madagascar region, and to compare the diversification of C3 and C4 taxa.
Location
Madagascar and the surrounding Indian Ocean islands, integrated within a global dataset.
Methods
We estimated 11 time‐calibrated molecular phylogenies including 73% of Madagascar's known grass flora (65% of endemics), using two calibration scenarios. Integrating the available sequences from worldwide grass species, a total of 1928 accessions were analysed. We tested range evolution models, estimated ancestral ranges, and compared the patterns of lineage accumulation between endemic C3 and C4 grasses.
Results
We recovered 69 lineages endemic to or with an estimated origin in the Madagascar region, 25 of them C3 and 44 C4. Range evolution analysis suggests widespread distance‐scaling of dispersal and strongest historical links to Africa. Extant grass diversity largely accumulated since the Miocene, with parallel increases in C3 and C4 taxa. Two large C3 groups in the “Forest shade clade” (Paniceae: Boivinellinae) and the bamboos (subtribe Hickeliinae) have an estimated origin in the Madagascar region. Divergences and crown ages of endemic C4 lineages largely coincide with the Miocene grassland expansion.
Main conclusions
Madagascar's extant grass flora is the result of multiple overseas dispersals, predominantly from Africa, and diversified from the Miocene onwards. C3 grasses are characterized by two large presumed in situ radiations of shade grasses in the Paniceae and bamboos. Endemic C4 lineages result from twice as many immigration events, resulting in smaller clades. Ages of C4 lineages are consistent with a Pliocene or Late Miocene origin of grasslands in Madagascar, but estimating the nature and expanse of such early grasslands will require further research.
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