Water stress as a factor influencing the distribution of the ericoid shrub Philippia evansii in the Natal Drakensberg mountains, South Africa

Xylem pressure potential (Ψp) was measured in Philippia evansii plants growing on a cool, south aspect and a warm, valley bottom site. There were no significant differences in the minimum Ψp values (min Ψp) between sites during the day despite differences in the water vapour pressure deficit (VPD). It is deduced that P. evansii plants are sensitive to water loss with Ψp values stabilizing at ca − 1100kPa by the control of transpirational flux. In spite of the higher VPD measured at the warmer site, pre-dawn values of Ψp (base Ψp) were more negative at the cool site. Since plants were experiencing water stress on the cool southern slopes at night, it appears that conditions on the northern slopes would be too dry for colonization by P. evansii plants. It is concluded that the indirect effects of radiation on the water balance are important factors controlling the distribution of P. evansii

Aluminium induced changes in the morphology of the quiescent centre, proximal meristem and growth region of the root of Zea mays

Treatment of the primary root with 8 mg dm-3 Al altered the pattern of cell growth so that with 48–h treatment, the root apex was no longer an organized, cytologically heterogeneous complex. An increase in mean cell volume was first observed with 2–h treatment, primarily in the cells of the quiescent centre where cell enlargement was associated with the removal of the constraint to quiescence by Al and in the mid-cortex 1–2 mm from the root tip where growth stimulation was associated with a departure from osmotic equilibrium. An initial increase in the osmotic potential of the root cell sap arising from Al treatment (1 h) was not maintained and subsequent decreases in the osmotic potential coincided with changes in the cell growth direction. Stress patterns arising from the anisotropic growth response of cortical cells with 20–h root exposure to Al were associated with the collapse of the conducting tissue of the stele and disintegration of the outer cells of the root. Advanced vacuolation of the cells of the root apex, first observed with 5–h treatment, was a feature of Al-stressed roots. Alteration to the nuclear structure in cells of the proximal meristem involving the degree of chromatin condensation and structure of the nucleolus was considered indicative of senescence. S. Afr. J. Bot. 1985, 51: 355–362Behandeling van die primêre wortel met 8 mg dm−3 Al het die patroon van selgroei verander, sodat die wortelpunt na blootstelling van 48 h nie meer ‘n sitologies-georganiseerde geheel was nie. ‘n Toename in die gemiddelde selvolume is na blootstelling van 2 h waargeneem, hoofsaaklik in die selle van die rustende gebied, waar die vergroting van selle geassosieer is met die opheffing van die rustoestand, en in die sentrale korteks, 1–2 mm vanaf die wortelpunt, waar die aanvangsgroei gestimuleer is deur ‘n afwyking vanaf osmotiese ewewig. Die aanvanklike verhoging in die osmotiese potensiaal van die selsap, as gevolg van die Al-behandeling (1 h), is nie volgehou nie; die verlaging in osmotiese potensiaal het ooreengestem met veranderings in die rigting van selgroei. Spanningspatrone wat voortspruit uit die anisotropiese groeireaksie van die korteksselle na 20 h se blootstelling van die wortel aan Al, is geassosieer met die ineenstorting van die geleidingsweefsel van die stele en die disintegrasie van die wortels se epidermis. Gevorderde vakuolering van die wortelpuntselle wat vir die eerste keer opgemerk is met die 5 h-blootstelling is ‘n kenmerk van wortels wat aan Al blootgestel is. Veranderings in die kernstruktuur van die selle van die proksimale meristeem ten opsigte van die graad van chromatienkondensering in die struktuur van die nukleolus is beskou as aanduidings van veroudering. S.-Afr. Tydskr. Plantk. 1985, 51: 355–36

Solving the Eating Disorders Puzzle Piece by Piece

Albeit slowly, we are beginning to piece together the complex biological puzzle of anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED). The article by Lutter et al. in this issue of Biological Psychiatry brings us one step closer to understanding these illnesses

Rigor and reproducibility in genetic research on eating disorders

Objective: We explored both within-method and between-method rigor and reproducibility in the field of eating disorders genetics. Method: We present critical evaluation and commentary on component methods of genetic research (family studies, twin studies, molecular genetic studies) and discuss both successful and unsuccessful efforts in the field. Results: Eating disorders genetics has had a number of robust results that converge across component methodologies. Familial aggregation of eating disorders, twin-based heritability estimates of eating disorders, and genome-wide association studies (GWAS) all point toward a substantial role for genetics in eating disorders etiology and support the premise that genes do not act alone. Candidate gene and linkage studies have been less informative historically. Discussion: The eating disorders field has entered the GWAS era with studies of anorexia nervosa. Continued growth of sample sizes is essential for rigorous discovery of actionable variation. Molecular genetic studies of bulimia nervosa, binge-eating disorder, and other eating disorders are virtually nonexistent and lag seriously behind other major psychiatric disorders. Expanded efforts are necessary to reveal the fundamental biology of eating disorders, inform clinical practice, and deliver new therapeutic targets

Botrytis cinerea loss and restoration of virulence during in vitro culture follows flux in global DNA methylation

Pathogenic fungi can lose virulence after protracted periods of culture, but little is known of the underlying mechanisms. Here, we present the first analysis of DNA methylation flux at a single-base resolution for the plant pathogen B. cinerea and identify differentially methylated genes/genomic regions associated with virulence erosion during in vitro culture. Cultures were maintained for eight months, with subcultures and virulence testing every month. Methylationsensitive amplified polymorphisms were performed at monthly intervals to characterise global changes to the pathogen’s genome during culture and also on DNA from mycelium inoculated onto Arabidopsis thaliana after eight months in culture. Characterisation of culture-induced epialleles was assessed by whole-genome re-sequencing and whole-genome bisulfite sequencing. Virulence declined with time in culture and recovered after inoculation on A. thaliana. Variation detected by methylation-sensitive amplified polymorphisms followed virulence changes during culture. Wholegenome (bisulfite) sequencing showed marked changes in global and local methylation during culture but no significant genetic changes. We imply that virulence is a non-essential plastic character that is at least partly modified by the changing levels of DNA methylation during culture. We hypothesise that changing DNA methylation during culture may be responsible for the high virulence/low virulence transition in B. cinerea and speculate that this may offer fresh opportunities to control pathogen virulence.James Breen, Luis Alejandro Jose Mur, Anushen Sivakumaran, Aderemi Akinyemi, Michael James Wilkinson, and Carlos Marcelino Rodriguez Lope

Conference Report: Psychiatric Genomics Consortium Meeting: Pathways to Drugs, London, March 2017

[No abstract available

Wine terroir and the soil bacteria: an amplicon sequencing-based assessment of the Barossa Valley and its sub-regions

A wines' terroir, represented as wine traits with regional distinctiveness, is a reflection of both the biophysical and human-driven conditions in which the grapes were grown and wine made. Soil is an important factor contributing to the uniqueness of a wine produced by vines grown in specific conditions. Here, we evaluated the impact of environmental variables on the soil bacteria of 22 Barossa Valley vineyard sites based on the 16S rRNA gene hypervariable region 4. In this study, we report that both dispersal isolation by geographic distance and environmental heterogeneity (soil plant-available P content, elevation, rainfall, temperature, spacing between row and spacing between vine) contribute to microbial community dissimilarity between vineyards. Vineyards located in cooler and wetter regions showed lower beta diversity and a higher ratio of dominant taxa. Differences in soil bacterial community composition were significantly associated with differences in fruit and wine composition. Our results suggest that environmental factors affecting wine terroir, may be mediated by changes in microbial structure, thus providing a basic understanding of how growing conditions affect interactions between plants and their soil bacteria.Jia Zhou, Timothy R. Cavagnaro, Roberta De Bei, Tiffanie M. Nelson, John R. Stephen, Andrew Metcalfe, Matthew Gilliham, James Breen, Cassandra Collins and Carlos M. Rodríguez Lópe

Significant locus and metabolic genetic correlations revealed in genome-wide association study of anorexia nervosa

OBJECTIVE: The authors conducted a genome-wide association study of anorexia nervosa and calculated genetic correlations with a series of psychiatric, educational, and metabolic phenotypes. METHOD: Following uniform quality control and imputation procedures using the 1000 Genomes Project (phase 3) in 12 case-control cohorts comprising 3,495 anorexia nervosa cases and 10,982 controls, the authors performed standard association analysis followed by a meta-analysis across cohorts. Linkage disequilibrium score regression was used to calculate genome-wide common variant heritability (single-nucleotide polymorphism [SNP]-based heritability [h2SNP]), partitioned heritability, and genetic correlations (rg) between anorexia nervosa and 159 other phenotypes. RESULTS: Results were obtained for 10,641,224 SNPs and insertion-deletion variants with minor allele frequencies >1% and imputation quality scores >0.6. The h2SNP of anorexia nervosa was 0.20 (SE=0.02), suggesting that a substantial fraction of the twin-based heritability arises from common genetic variation. The authors identified one genome-wide significant locus on chromosome 12 (rs4622308) in a region harboring a previously reported type 1 diabetes and autoimmune disorder locus. Significant positive genetic correlations were observed between anorexia nervosa and schizophrenia, neuroticism, educational attainment, and high-density lipoprotein cholesterol, and significant negative genetic correlations were observed between anorexia nervosa and body mass index, insulin, glucose, and lipid phenotypes. CONCLUSIONS: Anorexia nervosa is a complex heritable phenotype for which this study has uncovered the first genome-wide significant locus. Anorexia nervosa also has large and significant genetic correlations with both psychiatric phenotypes and metabolic traits. The study results encourage a reconceptualization of this frequently lethal disorder as one with both psychiatric and metabolic etiology

Psychiatric genomics: An update and an Agenda

The Psychiatric Genomics Consortium (PGC) is the largest consortium in the history of psychiatry. This global effort is dedicated to rapid progress and open science, and in the past decade it has delivered an increasing flow of new knowledge about the fundamental basis of common psychiatric disorders. The PGC has recently commenced a program of research designed to deliver “actionable” findings—genomic results that 1) reveal fundamental biology, 2) inform clinical practice, and 3) deliver new therapeutic targets. The central idea of the PGC is to convert the family history risk factor into biologically, clinically, and therapeutically meaningful insights. The emerging findings suggest that we are entering a phase of accelerated genetic discovery for multiple psychiatric disorders. These findings are likely to elucidate the genetic portions of these truly complex traits, and this knowledge can then be mined for its relevance for improved therapeutics and its impact on psychiatric practice within a precision medicine framework