Genetic polymorphism in Chondrilla (Asteraceae) in southern European Russia and the nature of Chondrilla juncea L

We studied genetic diversity in 54 populations of nine sexual and apomictic species of the genus Chondrilla (C. acantholepis, C. ambigua, C. brevirostris, C. canescens, C. graminea, C. juncea, C. laticoronata, C. latifolia and C. pauciflora) in SE European Russia and neighboring territories of NW Kazakhstan. We analysed the trnT–trnF region of plastid DNA and the internal transcribed spacer of ribosomal DNA (ITS1–5.8S–ITS2) using statistical parsimony, maximum likelihood and neighbor net methods. Two major evolutionary lineages, roughly corresponding to the two subgenera traditionally recognized in the region, were revealed. Within the first evolutionary lineage (subgenus Brachyrhynchus), the sexual diploid C. ambigua and its putatively hybrid apomictic derivatives C. brevirostris, C. laticoronata and C. pauciflora could be recognized. Their identity was also confirmed by analyses of ISSR markers. The second evolutionary lineage (subgenus Chondrilla) comprises C. juncea, C. acantholepis, C. canescens, C. graminea and C. latifolia in European Russia, but analyses of morphological variability and the genealogy of plastid and nuclear markers favor their treatment as the single facultatively apomictic species C. juncea. The results demonstrate that an apomictic mode of reproduction does not necessarily result in the formation of genetically separated microspecies.     

Prebiotic Syntheses Under Shock in the Water – Formamide – Potassium Bicarbonate – Sodium Hydroxide System

Origins of Life and Evolution of Biospheres - Syntheses under shock in nitrogen bubbled samples of the water – formamide – bicarbonate – sodium hydroxide system at...     

Evolution,diversity and interactions with past human populations of recently extinct Pholidoscelis lizards (Squamata: Teiidae) from the Guadeloupe Islands (French West-Indies)

This paper aims to demonstrate how subfossil bone remains from Pleistocene and Holocene deposits can help to reconstruct the history of recently extinct taxa through the example of Pholidoscelis lizards from the Guadeloupe Islands in the French West Indies. To achieve this, we conducted a new anatomical and zooarchaeological study of fossil Pholidoscelis remains collected from 23 archaeological and paleontological deposits on the Guadeloupe Islands from which this genus is nowadays absent. Our results shed light on the past existence of large Pholidoscelis lizards on all the Guadeloupe islands but also on the difficulties of confident specific identification for these remains. Nevertheless, we suggest a possible past occurrence of the now extinct Pholidoscelis major on nearly all of the Guadeloupe islands. In addition, we identified a new Pholidoscelis species, Pholidoscelis turukaeraensis sp. nov., on Marie-Galante Island, where no Pholidoscelis lizards were previously reported. This new species underwent an increase in size after the end of the Pleistocene period, possibly due to reduced predation pressure. We also highlight the consumption of Pholidoscelis lizards by pre-Columbian Amerindians and the huge impact of European colonization, which led to the extinction of all these lizards in less than 300 years.http://zoobank.org/urn:lsid:zoobank.org:pub:15C39436-A083-483F-B35E-78807B606904     

How Do Different Watering Regimes Affect the Growth,Chlorophyll Fluorescence,Phytohormone, and Phenolic Acid Content of Greenhouse-Grown Ceratotheca triloba?

We evaluated the effect of different watering regimes on the growth, chlorophyll fluorescence, phytohormones, and phenolic acids in Ceratotheca triloba (Bernh.) Hook.f., a commonly consumed African indigenous leafy vegetable. The study was conducted in the greenhouse under different watering regimes [seven (daily); three (thrice); two (twice); one (once) day(s) per week] for a period of 2 and 4-months. In each pot (7.5 cm diameter; 150 ml volume), 50 ml of water was applied per treatment. At the end of the experiment, plant growth, chlorophyll fluorescence, phytohormones, and phenolic acids were determined. A decrease in water availability resulted in a consistent decline in plant growth after a 4-month growth period. The severity of reduced water availability was more noticeable in plants watered once a week with a 1.4-fold reduction in growth and quantum efficiency of PSII (Fv/Fm) value of 0.80. The significant decline in growth and chlorophyll fluorescence was probably due to the increased production of abscisic acid (ABA) and cytokinin (CK) content together with the detected phytohormones in plants with restricted water supply. Furthermore, plants watered once a week had a trade-off between growth and phenolic acid production, with significantly higher (threefolds) concentrations of vanillic, ferulic, caffeic, and 4-coumaric acids in 4-month-old plants. Even though C. triloba grew best in well-watered soil, the plant had the potential to adapt and survive in soils with limited water supply for longer periods of growth. These findings suggest that regulation of phytohormones and phenolic acids played an important role in improving the growth of C. triloba under limited water conditions.

     

Distribution,degree of damage and risk of spread of Trioza erytreae (Hemiptera: Triozidae) in Kenya

The African citrus triozid (ACT), Trioza erytreae Del Guercio, is a destructive pest particularly on citrus, and vectors, “Candidatus” Liberibacter africanus (CLaf), which is the causal agent of the African citrus greening disease. Our study seeks to establish the distribution and host‐plant relationship of ACT across citrus production areas in Kenya. We also modelled the risk of spread using the maximum entropy modelling algorithm with known occurrence data. Our results infer that ACT is widely distributed and causes severe damage to four alternative host plants belonging to the family Rutaceae. The adults, immature stages (eggs and nymphs), galls and the percentage of infested leaves were significantly higher in shaded than unshaded trees. However, adult ACTs preferred Kenyan highlands to Victoria Lake and coastal regions. The average area under the curve of the model predictions was 0.97, indicating an optimal model performance. The environmental variables that most influenced the prediction were the precipitation of wettest quarter, precipitation of wettest month, mean diurnal range, temperature seasonality and mean temperature of the coldest quarter. The current prediction of ACT exceeded its existing range, especially in the Western, Nyanza, Central, Rift valley and Eastern regions of Kenya. The model predicted a contraction of suitable habitats for a potential spread in 2040 with an inland shift to higher altitudes in the cooler regions. The potential for further expansion to climatically suitable areas was more pronounced for the 2080 forecast. These findings provide relevant information to improve monitoring/surveillance and designing IPM strategies to limit its spread and damage.     

Efficient target cleavage by Type V Cas12a effectors programmed with split CRISPR RNA

CRISPR RNAs (crRNAs) that direct target DNA cleavage by Type V Cas12a nucleases consist of constant repeat-derived 5′-scaffold moiety and variable 3′-spacer moieties. Here, we demonstrate that removal of most of the 20-nucleotide scaffold has only a slight effect on in vitro target DNA cleavage by a Cas12a ortholog from Acidaminococcus sp. (AsCas12a). In fact, residual cleavage was observed even in the presence of a 20-nucleotide crRNA spacer moiety only. crRNAs split into separate scaffold and spacer RNAs catalyzed highly specific and efficient cleavage of target DNA by AsCas12a in vitro and in lysates of human cells. In addition to dsDNA target cleavage, AsCas12a programmed with split crRNAs also catalyzed specific ssDNA target cleavage and non-specific ssDNA degradation (collateral activity). V-A effector nucleases from Francisella novicida (FnCas12a) and Lachnospiraceae bacterium (LbCas12a) were also functional with split crRNAs. Thus, the ability of V-A effectors to use split crRNAs appears to be a general property. Though higher concentrations of split crRNA components are needed to achieve efficient target cleavage, split crRNAs open new lines of inquiry into the mechanisms of target recognition and cleavage and may stimulate further development of single-tube multiplex and/or parallel diagnostic tests based on Cas12a nucleases.     

A locus conferring tolerance to Theileria infection in African cattle

East Coast fever, a tick-borne cattle disease caused by the Theileria parva parasite, is among the biggest natural killers of cattle in East Africa, leading to over 1 million deaths annually. Here we report on the genetic analysis of a cohort of Bos indicus (Boran) cattle demonstrating heritable tolerance to infection with T. parva (h² = 0.65, s.e. 0.57). Through a linkage analysis we identify a 6 Mb genomic region on bovine chromosome 15 that is significantly associated with survival outcome following T. parva exposure. Testing this locus in an independent cohort of animals replicates this association with survival following T. parva infection. A stop gained variant in a paralogue of the FAF1 gene in this region was found to be highly associated with survival across both related and unrelated animals, with only one of the 20 homozygote carriers (T/T) of this change succumbing to the disease in contrast to 44 out of 97 animals homozygote for the reference allele (C/C). Consequently, we present a genetic locus linked to tolerance of one of Africa’s most important cattle diseases, raising the promise of marker-assisted selection for cattle that are less susceptible to infection by T. parva.     

Drug development for the treatment of onchocerciasis: Population pharmacokinetic and adverse events modeling of emodepside

BackgroundTo accelerate the progress towards onchocerciasis elimination, a macrofilaricidal drug that kills the adult parasite is urgently needed. Emodepside has shown macrofilaricidal activity against a variety of nematodes and is currently under clinical development for the treatment of onchocerciasis. The aims of this study were i) to characterize the population pharmacokinetic properties of emodepside, ii) to link its exposure to adverse events in healthy volunteers, and iii) to propose an optimized dosing regimen for a planned phase II study in onchocerciasis patients.Methodology / Principal findingsPlasma concentration-time profiles and adverse event data were obtained from 142 subjects enrolled in three phase I studies, including a single-dose, and a multiple-dose, dose-escalation study as well as a relative bioavailability study. Nonlinear mixed-effects modeling was used to evaluate the population pharmacokinetic properties of emodepside. Logistic regression modeling was used to link exposure to drug-related treatment-emergent adverse events (TEAEs). Emodepside pharmacokinetics were well described by a transit-absorption model, followed by a 3-compartment disposition model. Body weight was included as an allometric function and both food and formulation had a significant impact on absorption rate and relative bioavailability. All drug-related TEAEs were transient, and mild or moderate in severity. An increase in peak plasma concentration was associated with an increase in the odds of experiencing a drug-related TEAE of interest.Conclusions/SignificancePharmacokinetic modeling and simulation was used to derive an optimized, body weight-based dosing regimen, which allows for achievement of extended emodepside exposures above target concentrations while maintaining acceptable tolerability margins.