How quick was marine recovery after the end-Triassic mass extinction and what role did anoxia play?

Oxygen restricted conditions were widespread in European shelf seas after the end-Triassic mass extinction event and they are reported to have hindered the recovery of marine benthos. Here we reconstruct the redox history of the Early Jurassic Blue Lias Formation of southwest Britain using pyrite framboid size analysis and compare this with the recovery of bivalves based on field and museum collections. Results suggest widespread dysoxia punctuated by periods of anoxia in the region, with the latter developing frequently in deeper water settings. Despite these harsh conditions, initial benthic recovery occurred rapidly in the British Jurassic, especially in shallowest settings, and shows no relationship with the intensity of dysoxia. A stable diversity was reached by the first recognised ammonite zone after the end-Triassic mass extinction. This contrasts with the deeper-water, more oxygen-poor sections where the diversity increase was still continuing in the earliest Sinemurian Stage, considerably longer than previously reported. Similar recovery rates are seen amongst other groups (brachiopods and ammonites). Oxygen-poor conditions have been suggested to delay recovery after the Permo-Triassic mass extinction, but this is not the case after the end-Triassic crisis. We suggest that this was because the European dysoxia was only a regional phenomenon and there were plenty of well-ventilated regions available to allow an untrammelled bounce back

The novel proteins Rng8 and Rng9 regulate the myosin-V Myo51 during fission yeast cytokinesis.

The myosin-V family of molecular motors is known to be under sophisticated regulation, but our knowledge of the roles and regulation of myosin-Vs in cytokinesis is limited. Here, we report that the myosin-V Myo51 affects contractile ring assembly and stability during fission yeast cytokinesis, and is regulated by two novel coiled-coil proteins, Rng8 and Rng9. Both rng8Δ and rng9Δ cells display similar defects as myo51Δ in cytokinesis. Rng8 and Rng9 are required for Myo51's localizations to cytoplasmic puncta, actin cables, and the contractile ring. Myo51 puncta contain multiple Myo51 molecules and walk continuously on actin filaments in rng8(+) cells, whereas Myo51 forms speckles containing only one dimer and does not move efficiently on actin tracks in rng8Δ. Consistently, Myo51 transports artificial cargos efficiently in vivo, and this activity is regulated by Rng8. Purified Rng8 and Rng9 form stable higher-order complexes. Collectively, we propose that Rng8 and Rng9 form oligomers and cluster multiple Myo51 dimers to regulate Myo51 localization and functions

Mendelian adult-onset leukodystrophy genes in Alzheimer´s disease. Critical influence of CSF1R and NOTCH3

Mendelian adult-onset leukodystrophies are a spectrum of rare inherited progressive neurodegenerative disorders affecting the white matter of the central nervous system. Among these, Cerebral Autosomal Dominant and Recessive Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL and CARASIL), Cerebroretinal vasculopathy (CRV), Metachromatic leukodystrophy (MLD), Hereditary diffuse Leukoencephalopathy with spheroids (HDLS), Vanishing white matter disease (VWM) present with rapidly progressive dementia as dominant feature and are caused by mutations in NOTCH3, HTRA1, TREX1, ARSA, CSF1R, EIF2B1, EIF2B2, EIF2B3, EIF2B4, EIF2B5, respectively. Given the rare incidence of these disorders and the lack of unequivocally diagnostic features, leukodystrophies are frequently misdiagnosed with common sporadic dementing diseases such as Alzheimer’s disease (AD), raising the question of whether these overlapping phenotypes may be explained by shared genetic risk factors. To investigate this intriguing hypothesis, we have combined gene expression analysis 1) in 6 different AD mouse strains (APPPS1, HOTASTPM, HETASTPM, TPM, TAS10 and TAU), at 5 different developmental stages (Embryo [E15], 2 months, 4 months, 8 months and 18 months), 2) in APPPS1 primary cortical neurons under stress conditions (oxygen-glucose deprivation) and single-variant and single-gene (c-alpha and SKAT tests) based genetic screening in a cohort composed of 332 Caucasian late-onset AD patients and 676 Caucasian elderly controls. Csf1r was significantly overexpressed (Log2FC>1, adj. p-val<0.05) in the cortex and hippocampus of aged HOTASTPM mice with extensive Aβ core dense plaque pathology. We identified 3 likely pathogenic mutations in CSF1R TK domain (p.L868R, p.Q691H and p.H703Y) in our discovery and validation cohort, composed of 465 AD and MCI Caucasian patients from the UK. Moreover, NOTCH3 was a significant hit in the c-alpha test (adj p-val = 0.01). Adult onset Mendelian leukodystrophy genes are not common factors implicated in AD. Nevertheless, our study suggests a potential pathogenic link between NOTCH3, CSF1R and sporadic LOAD, that warrants further investigation

Body size trends and recovery amongst bivalves following the end-Triassic mass extinction

Fossils in the immediate aftermath of mass extinctions are often of small size, a phenomenon attributed to the Lilliput Effect (temporary, size reduction of surviving species). There has been little attempt to study size trends during subsequent recovery intervals nor has the relationship between size, diversity and environmental controls been evaluated. Here we examine the recovery following the end-Triassic mass extinction amongst bivalves of the British Lower and Middle Lias. Three distinct phases of size change are seen that are independent of other recovery metrics: initially bivalves are small but the Lilliput Effect is a minor factor, the majority of small taxa belong to new species that undergo a later within-species size increase (the Brobdingnag Effect) throughout the subsequent Hettangian Stage. New species that appeared during the Hettangian were also progressively larger and Cope's Rule (size increase between successive species) is seen – notably amongst ammonites. The size increase was reversed during the Sinemurian Stage, when bivalves once again exhibited small body sizes. During the Pliensbachian Stage another phase of size increase occurred with further evidence of the Brobdingnag Effect. These three phases of size change are seen across all suspension feeding ecological guilds of bivalve but are not expressed among deposit feeders. Local environmental conditions explain some aspects of size patterns, but factors such as temperature, marine oxygenation and sea level, do not correlate with the long-term size trends. The Brobdingnag Effect may reflect increased availability/quality of food during the recovery interval: a factor that controlled bivalve size but not evolution

Hybrid-maize—a maize simulation model that combines two crop modeling approaches

A new maize (Zea mays L.) simulation model, Hybrid-Maize, was developed by combining the strengths of two modeling approaches: the growth and development functions in maize-specific models represented by CERES- Maize, and the mechanistic formulation of photosynthesis and respiration in generic crop models such as INTERCOM and WOFOST. It features temperature-driven maize phenological development, vertical canopy integration of photosynthesis, organ-specific growth respiration, and temperature-sensitive maintenance respiration. The inclusion of gross assimilation, growth respiration and maintenance respiration makes the Hybrid- Maize model potentially more responsive to changes in environmental conditions than models such as CERES-Maize. Hybrid-Maize also requires fewer genotype-specific parameters without sacrificing prediction accuracy. A linear relationship between growing degree-days (GDD) from emergence to silking and GDD from emergence to physiological maturity was used for prediction of day of silking when the former is not available. The total GDD is readily available for most commercial maize hybrids. Preliminary field evaluations at two locations under high-yielding growth conditions indicated close agreement between simulated and measured values for leaf area, dry matter accumulation, final grain and stover yields, and harvest index (HI). Key areas for further model improvement include LAI prediction at high plant density, and biomass partitioning, carbohydrate translocation, and maintenance respiration in response to above-average temperature, especially during reproductive growth. The model has not been evaluated under conditions of water and/or nutrient stress, and efforts are currently in progress to develop and validate water and nitrogen balance components for the Hybrid- Maize model