A multi-environmental study of recent breeding progress on nitrogen use efficiency in wheat (Triticum aestivum L.)

Key message

By comparing 195 varieties in eight trials, this study assesses nitrogen use efficiency improvement in high and low nitrogen conditions in European winter wheat over the last 25 years.

Abstract

In a context where European agriculture practices have to deal with environmental concerns and nitrogen (N) fertiliser cost, nitrogen use efficiency (NUE) has to be improved. This study assessed genetic progress in winter wheat (Triticum aestivum L.) NUE. Two hundred and twenty-five European elite varieties were tested in four environments under two levels of N. Global genetic progress was assessed on additive genetic values and on genotype × N interaction, covering 25 years of European breeding. To avoid sampling bias, quality, precocity and plant height were added as covariates in the analyses when needed. Genotype × environment interactions were highly significant for all the traits studied to such an extent that no additive genetic effect was detected on N uptake. Genotype × N interactions were significant for yield, grain protein content (GPC), N concentration in straw, N utilisation, and NUE. Grain yield improvement (+0.45 % year^?1) was independent of the N treatment. GPC was stable, thus grain nitrogen yield was improved (+0.39 % year^?1). Genetic progress on N harvest index (+0.12 % year^?1) and on N concentration in straw (?0.52 % year^?1) possibly revealed improvement in N remobilisation. There has been an improvement of NUE additive genetic value (+0.33 % year^?1) linked to better N utilisation (+0.20 % year^?1). Improved yield stability was detected as a significant improvement of NUE in low compared to high N conditions. The application of these results to breeding programs is discussed.     

New skull of Lesothosaurus (Dinosauria: Ornithischia) from the Upper Elliot Formation (Lower Jurassic) of southern Africa

A new ornithischian skull from the Elliot Formation of southern Africa is described. The specimen is compared in detail with the fabrosaurid Lesothosaurus diagnosticus. It actually shares many characters with specimens of the syntypes of this species or specimens referred to it. It is nevertheless not identical to any of these specimens and it is, moreover, remarkably larger than them. The possibility of attributing this specimen to a so far undescribed ‘large fabrosaur’ from the same formation is discussed. It is concluded that the specimen in question in this paper, while being ascribable to the genus Lesothosaurus, cannot be determined to a specific level until the existence of two fabrosaurid species in the ‘Stormberg Group’ is demonstrated and their range of morphological and size variation is properly appraised.     

Influence of body reserves and eye opacity on foraging behaviours of tiger snakes

Physiological states such as reproductive stage, parasite load, body condition, and environmental conditions, influence behaviours in complex ways. According to the Clark's asset-protection principle (Clark, 1994. Behav Ecol 5:159-170), individuals in good body condition take fewer predation risks than conspecifics in lesser condition. In many ectotherms, foraging, digestion, and moulting require an elevation of the metabolism achieved through intensive basking, thereby increasing the risk of being detected by predators. Using four experimental groups of snakes, we showed that two independent physiological states, (1) the presence of prey in the stomach and (2) eye opacity associated with moulting, increase predator vulnerability. In a parallel experiment, two groups of snakes were maintained on contrasting diets (high food intake vs. low food intake) for 6 months. Apart from sloughing periods, most individuals (89%) accepted their meal irrespective of food treatment. Consequently, well-fed snakes exhibited higher body condition (one third physiological state) relative to less-fed individuals. During sloughing events, however, well-fed individuals often refused (78%) to eat while the less-fed individuals readily accepted (86%) their meal despite eye opacity. Individuals with less body reserves accepted the cumulative risks owing to eye opacity and stomach fullness. By contrast, well-fed snakes remained more "prudent" (i.e., exhibited behaviours that depended on their internal state). Our results show that snakes can adjust their foraging "decision" by combining different physiological informations.     

Human Discs Large is a new negative regulator of human immunodeficiency virus-1 infectivity

Human immunodeficiency virus (HIV)-1 replication is positively or negatively regulated through multiple interactions with host cell proteins. We report here that human Discs Large (Dlg1), a scaffold protein recruited beneath the plasma membrane and involved in the assembly of multiprotein complexes, restricts HIV-1 infectivity. The endogenous Dlg1 and HIV-1 Gag polyprotein spontaneously interact in HIV-1-chronically infected T cells. Depleting endogenous Dlg1 in either adherent cells or T cells does not affect Gag maturation, production, or release, but it enhances the infectivity of progeny viruses five- to sixfold. Conversely, overexpression of Dlg1 reduces virus infectivity by ~80%. Higher virus infectivity upon Dlg1 depletion correlates with increased Env content in cells and virions, whereas the amount of virus-associated Gag or genomic RNA remains identical. Dlg1 knockdown is also associated with the redistribution and colocalization of Gag and Env toward CD63 and CD82 positive vesicle-like structures, including structures that seem to still be connected to the plasma membrane. This study identifies both a new negative regulator that targets the very late steps of the HIV-1 life cycle, and an assembly pathway that optimizes HIV-1 infectivity.     

High‐Throughput DNA sequencing of ancient wood

Reconstructing the colonization and demographic dynamics that gave rise to extant forests is essential to forecasts of forest responses to environmental changes. Classical approaches to map how population of trees changed through space and time largely rely on pollen distribution patterns, with only a limited number of studies exploiting DNA molecules preserved in wooden tree archaeological and subfossil remains. Here, we advance such analyses by applying high‐throughput (HTS) DNA sequencing to wood archaeological and subfossil material for the first time, using a comprehensive sample of 167 European white oak waterlogged remains spanning a large temporal (from 550 to 9,800 years) and geographical range across Europe. The successful characterization of the endogenous DNA and exogenous microbial DNA of 140 (~83%) samples helped the identification of environmental conditions favouring long‐term DNA preservation in wood remains, and started to unveil the first trends in the DNA decay process in wood material. Additionally, the maternally inherited chloroplast haplotypes of 21 samples from three periods of forest human‐induced use (Neolithic, Bronze Age and Middle Ages) were found to be consistent with those of modern populations growing in the same geographic areas. Our work paves the way for further studies aiming at using ancient DNA preserved in wood to reconstruct the micro‐evolutionary response of trees to climate change and human forest management.     

On-Going Frontal Alpha Rhythms Are Dominant in Passive State and Desynchronize in Active State in Adult Gray Mouse Lemurs

The gray mouse lemur (Microcebus murinus) is considered a useful primate model for translational research. In the framework of IMI PharmaCog project (Grant Agreement n°115009, www.pharmacog.org), we tested the hypothesis that spectral electroencephalographic (EEG) markers of motor and locomotor activity in gray mouse lemurs reflect typical movement-related desynchronization of alpha rhythms (about 8–12 Hz) in humans. To this aim, EEG (bipolar electrodes in frontal cortex) and electromyographic (EMG; bipolar electrodes sutured in neck muscles) data were recorded in 13 male adult (about 3 years) lemurs. Artifact-free EEG segments during active state (gross movements, exploratory movements or locomotor activity) and awake passive state (no sleep) were selected on the basis of instrumental measures of animal behavior, and were used as an input for EEG power density analysis. Results showed a clear peak of EEG power density at alpha range (7–9 Hz) during passive state. During active state, there was a reduction in alpha power density (8–12 Hz) and an increase of power density at slow frequencies (1–4 Hz). Relative EMG activity was related to EEG power density at 2–4 Hz (positive correlation) and at 8–12 Hz (negative correlation). These results suggest for the first time that the primate gray mouse lemurs and humans may share basic neurophysiologic mechanisms of synchronization of frontal alpha rhythms in awake passive state and their desynchronization during motor and locomotor activity. These EEG markers may be an ideal experimental model for translational basic (motor science) and applied (pharmacological and non-pharmacological interventions) research in Neurophysiology.     

A robust approach to estimate relative phytoplankton cell abundances from metagenomes

Phytoplankton account for >45% of global primary production, and have an enormous impact on aquatic food webs and on the entire Earth System. Their members are found among prokaryotes (cyanobacteria) and multiple eukaryotic lineages containing chloroplasts. Genetic surveys of phytoplankton communities generally consist of PCR amplification of bacterial (16S), nuclear (18S) and/or chloroplastic (16S) rRNA marker genes from DNA extracted from environmental samples. However, our appreciation of phytoplankton abundance or biomass is limited by PCR-amplification biases, rRNA gene copy number variations across taxa, and the fact that rRNA genes do not provide insights into metabolic traits such as photosynthesis. Here, we targeted the photosynthetic gene psbO from metagenomes to circumvent these limitations: the method is PCR-free, and the gene is universally and exclusively present in photosynthetic prokaryotes and eukaryotes, mainly in one copy per genome. We applied and validated this new strategy with the size-fractionated marine samples collected by Tara Oceans, and showed improved correlations with flow cytometry and microscopy than when based on rRNA genes. Furthermore, we revealed unexpected features of the ecology of these ecosystems, such as the high abundance of picocyanobacterial aggregates and symbionts in the ocean, and the decrease in relative abundance of phototrophs towards the larger size classes of marine dinoflagellates. To facilitate the incorporation of psbO in molecular-based surveys, we compiled a curated database of >18,000 unique sequences. Overall, psbO appears to be a promising new gene marker for molecular-based evaluations of entire phytoplankton communities.     

Genetic signatures of a range expansion in natura: when clones play leapfrog

The genetic consequences of range expansions have generally been investigated at wide geographical and temporal scales, long after the colonization event. A unique ecological system enabled us to both monitor the colonization dynamics and decipher the genetic footprints of expansion over a very short time period. Each year an epidemic of the poplar rust (Melampsora larici‐populina) expands clonally and linearly along the Durance River, in the Alps. The colonization dynamics observed in 2004 showed two phases with different genetic outcomes. Upstream, fast colonization maintained high genetic diversity. Downstream, the colonization wave progressively faltered, diversity eroded, and differentiation increased, as expected under recurrent founder events. In line with the high dispersal abilities of rust pathogens, we provide evidence for leapfrog dispersal of clones. Our results thus emphasize the importance of colonization dynamics in shaping spatial genetic structure in the face of high gene flow.     

Discovery and structure-guided drug design of inhibitors of 11β-hydroxysteroid-dehydrogenase type I based on a spiro-carboxamide scaffold

Spiro-carboxamides were identified as inhibitors of 11β-hydroxysteroid-dehydrogenase type 1 by high-throughput screening. Structure-based drug design was used to optimise the initial hit yielding a sub-nanomolar IC₅₀ inhibitor (0.5 nM) on human 11β-HSD1 with a high binding efficiency index (BEI of 32.7) which was selective against human 11β-HSD2 (selectivity ratio > 200000).