Characterising heart rhythm abnormalities associated with Xp22.31 deletion.

BACKGROUND: Genetic deletions at Xp22.31 are associated with the skin condition X linked ichthyosis (XLI), and with a substantially increased risk of atrial fibrillation/flutter (AF), in males. AF is associated with elevated thrombosis, heart failure, stroke and dementia risk. METHODS: Through: (a) examining deletion carriers with a diagnosis of AF in UK Biobank, (b) undertaking an online survey regarding abnormal heart rhythms (AHRs) in men/boys with XLI and female carriers of XLI-associated deletions and (c) screening for association between common genetic variants within Xp22.31 and idiopathic AF-related conditions in UK Biobank, we have investigated how AHRs manifest in deletion carriers, and have identified associated risk factors/comorbidities and candidate gene(s). Finally, we examined attitudes towards heart screening in deletion carriers. RESULTS: We show that AHRs may affect up to 35% of deletion carriers (compared with <20% of age-matched non-carriers), show no consistent pattern of onset but may be precipitated by stress, and typically resolve quickly and respond well to intervention. Gastrointestinal (GI) conditions and asthma/anaemia were the most strongly associated comorbidities in male and female deletion carriers with AHR, respectively. Genetic analysis indicated significant enrichment of common AF risk variants around STS (7 065 298-7 272 682 bp in GRCh37/hg19 genome build) in males, and of common GI disorder and asthma/anaemia risk variants around PNPLA4 (7 866 804-7 895 780 bp) in males and females, respectively. Deletion carriers were overwhelmingly in favour of cardiac screening implementation. CONCLUSION: Our data suggest AHRs are frequently associated with Xp22.31 deletion, and highlight subgroups of deletion carriers that may be prioritised for screening. Examining cardiac function further in deletion carriers, and in model systems lacking steroid sulfatase, may clarify AF pathophysiology.

Medical and neurobehavioural phenotypes in male and female carriers of Xp22.31 duplications in the UK Biobank.

Deletions spanning the STS (steroid sulfatase) gene at Xp22.31 are associated with X-linked ichthyosis, corneal opacities, testicular maldescent, cardiac arrhythmia, and higher rates of developmental and mood disorders/traits, possibly related to the smaller volume of some basal ganglia structures. The consequences of duplication of the same genomic region have not been systematically assessed in large or adult samples, although evidence from case reports/series has indicated high rates of developmental phenotypes. We compared multiple measures of physical and mental health, cognition and neuroanatomy in male (n = 414) and female (n = 938) carriers of 0.8-2.5 Mb duplications spanning STS, and non-carrier male (n = 192, 826) and female (n = 227, 235) controls from the UK Biobank (recruited aged 40-69 from the UK general population). Clinical and self-reported diagnoses indicated a higher prevalence of inguinal hernia and mania/bipolar disorder respectively in male duplication carriers, and a higher prevalence of gastro-oesophageal reflux disease and blistering/desquamating skin disorder respectively in female duplication carriers; duplication carriers also exhibited reductions in several depression-related measures, and greater happiness. Cognitive function and academic achievement did not differ between comparison groups. Neuroanatomical analysis suggested greater lateral ventricle and putamen volume in duplication carriers. In conclusion, Xp22.31 duplications appear largely benign, but could slightly increase the likelihood of specific phenotypes (although results were only nominally-significant). In contrast to deletions, duplications might protect against depressive symptoms, possibly via higher STS expression/activity (resulting in elevated endogenous free steroid levels), and through contributing towards an enlarged putamen volume. These results should enable better genetic counselling of individuals with Xp22.31 microduplications.

Mood symptoms, neurodevelopmental traits, and their contributory factors in X-linked ichthyosis, ichthyosis vulgaris and psoriasis.

BACKGROUND: High rates of adverse mood/neurodevelopmental traits are seen in multiple dermatological conditions, and can significantly affect patient quality of life. Understanding the sex-specific nature, magnitude, impact and basis of such traits in lesser-studied conditions like ichthyosis, is important for developing effective interventions. AIM: To quantify and compare relevant psychological traits in men with X-linked ichthyosis (XLI, n = 54) or in XLI carrier women (n = 83) and in patients with ichthyosis vulgaris (IV, men n = 23, women n = 59) or psoriasis (men n = 30, women n = 122), and to identify factors self-reported to contribute most towards depressive, anxious and irritable phenotypes. METHODS: Participants recruited via relevant charities or social media completed an online survey of established questionnaires. Data were analysed by sex and skin condition, and compared with general population data. RESULTS: Compared with the general population, there was a higher rate of lifetime prevalence of mood disorder diagnoses across all groups and of neurodevelopmental disorder diagnoses in the XLI groups. The groups exhibited similarly significant elevations in recent mood symptoms (Cohen d statistic 0.95-1.28, P < 0.001) and neurodevelopmental traits (d = 0.31-0.91, P < 0.05) compared with general population controls, and self-reported moderate effects on quality of life and stigmatization. There were strong positive associations between neurodevelopmental traits and recent mood symptoms (r > 0.47, P < 0.01), and between feelings of stigmatization and quality of life, particularly in men. Numerous factors were identified as contributing significantly to mood symptoms in a condition or sex-specific, or condition or sex-independent, manner. CONCLUSION: We found that individuals with XLI, IV or psoriasis show higher levels of mood disorder diagnoses and symptoms than matched general population controls, and that the prevalence and severity of these is similar across conditions. We also identified a number of factors potentially conferring either general or condition-specific risk of adverse mood symptoms in the three skin conditions, which could be targeted clinically and/or through education programmes. In clinical practice, recognizing mood/neurodevelopmental problems in ichthyosis and psoriasis, and addressing the predisposing factors identified by this study should benefit the mental health of affected individuals.

Digitally enabled cardiac rehabilitation following coronary revascularization: results from a single centre feasibility study.

Wearable activity monitors, together with smartphone-based health and fitness applications (apps), are becoming more accessible and their widespread use provides an additional opportunity for the recording of cardiovascular metrics in patients with cardiovascular disease. The use of selected metrics by cardiac rehabilitation (CR) programmes allows the facilitation of individualized and tailored positive lifestyle changes to patients and places the patient at the centre of their recovery programme. To investigate the role of such devices on outcomes with patients on a CR programme, a cohort/case-control study was conducted. Patients post-myocardial infarction who were treated with either percutaneous coronary intervention or surgical coronary revascularisation at a single centre were invited to use a physical activity monitor linked to a customized app at their initial assessment for the rehabilitation programme. Those who accepted were allocated to the treatment group. The control group was selected from a larger pool of 400 historical and concurrent patients. Propensity matching was used to associate each case with their closest control. The changes in self-reported physical activity were similar for both groups at the end of the CR programme (EOP). The digitally monitored group tended to achieve greater METS (metabolic equivalent of task - a measure of exercise intensity) at 12 weeks (P < 0.059); however, no difference was observed in the overall change in METS at EOP (P < 0.333). Although no difference was noted in diastolic blood pressure, a statistically significant drop in the systolic blood pressure in the digitally monitored group (P < 0.004) was detected. In this study, the innovative combination of technology and face-to-face CR showed promising results and assisted the individualization of delivered content. This intervention could easily be replicated and expanded. Challenges are the recruitment of the elderly population, those who may be less engaged with or have less access to technology, and the underrepresentation of women in the study sample.

Stronger Subjects Select a Movement Pattern That May Reduce Anterior Cruciate Ligament Loading During Cutting.

ABSTRACT: Davies, WT, Ryu, JH, Graham-Smith, P, Goodwin, JE, and Cleather, DJ. Stronger subjects select a movement pattern that may reduce anterior cruciate ligament loading during cutting. J Strength Cond Res 36(7): 1853-1859, 2022-Increased strength has been suggested to reduce the incidence of anterior cruciate ligament (ACL) injury as part of wider neuromuscular training programs; however, the mechanism of this is not clear. Cutting is a high-risk maneuver for ACL injury, but limited research exists as to how strength affects sagittal plane biomechanics during this movement. Sixteen subjects were split into a stronger and weaker group based on their relative peak isometric strength in a unilateral squat (stronger: 29.0 ± 3.4 N·kg-1 and weaker: 18.3 ± 4.1 N·kg-1). Subjects performed 45° cuts with maximal intent 3 times, at 3 different approach velocities (2, 4, and 6 m·s-1). Kinematics and ground reaction forces were collected using optical motion capture and a force platform. The stronger group had lower knee extensor moments, larger hip extensor moments, and a greater peak knee flexion angle than the weaker group (p < 0.05). There was a trend for greater knee flexion at initial contact in the stronger group. There were no differences in resultant ground reaction forces between groups. The stronger group relied more on the hip than the knee during cutting and reached greater knee flexion angles. This could decrease ACL loading by reducing the extensor moment required at the knee during weight acceptance. Similarly, the greater knee flexion angle during weight acceptance is likely to be protective of the ACL.

Medical and neurobehavioural phenotypes in carriers of X-linked ichthyosis-associated genetic deletions in the UK Biobank.

BACKGROUND: X-linked ichthyosis (XLI) is an uncommon dermatological condition resulting from a deficiency of the enzyme steroid sulfatase (STS), often caused by X-linked deletions spanning STS. Some medical comorbidities have been identified in XLI cases, but small samples of relatively young patients has limited this. STS is highly expressed in subcortical brain structures, and males with XLI and female deletion carriers appear at increased risk of developmental/mood disorders and associated traits; the neurocognitive basis of these findings has not been examined. METHODS: Using the UK Biobank resource, comprising participants aged 40-69 years recruited from the general UK population, we compared multiple medical/neurobehavioural phenotypes in males (n=86) and females (n=312) carrying genetic deletions spanning STS (0.8-2.5 Mb) (cases) to male (n=190 577) and female (n=227 862) non-carrier controls. RESULTS: We identified an elevated rate of atrial fibrillation/flutter in male deletion carriers (10.5% vs 2.7% in male controls, Benjamini-Hochberg corrected p=0.009), and increased rates of mental distress (p=0.003), irritability (p<0.001) and depressive-anxiety traits (p<0.05) in male deletion carriers relative to male controls completing the Mental Health Questionnaire. While academic attainment was unaffected, male and female deletion carriers exhibited impaired performance on the Fluid Intelligence Test (Cohen's d≤0.05, corrected p<0.1). Neuroanatomical analysis in female deletion carriers indicated reduced right putamen and left nucleus accumbens volumes (Cohen's d≤0.26, corrected p<0.1). CONCLUSION: Adult males with XLI disease-causing deletions are apparently at increased risk of cardiac arrhythmias and self-reported mood problems; altered basal ganglia structure may underlie altered function and XLI-associated psychiatric/behavioural phenotypes. These results provide information for genetic counselling of deletion-carrying individuals and reinforce the need for multidisciplinary medical care.

A new molecular risk pathway for postpartum mood disorders: clues from steroid sulfatase-deficient individuals.

Postpartum mood disorders develop shortly after childbirth in a significant proportion of women. These conditions are associated with a range of symptoms including abnormally high or low mood, irritability, cognitive disorganisation, disrupted sleep, hallucinations/delusions, and occasionally suicidal or infanticidal ideation; if not treated promptly, they can substantially impact upon the mother's health, mother-infant bonding, and family dynamics. The biological precipitants of such disorders remain unclear, although large changes in maternal immune and hormonal physiology following childbirth are likely to play a role. Pharmacological therapies for postpartum mood disorders can be effective, but may be associated with side effects, concerns relating to breastfeeding, and teratogenicity risks when used prophylactically. Furthermore, most of the drugs that are used to treat postpartum mood disorders are the same ones that are used to treat mood episodes during non-postpartum periods. A better understanding of the biological factors predisposing to postpartum mood disorders would allow for rational drug development, and the identification of predictive biomarkers to ensure that 'at risk' mothers receive earlier and more effective clinical management. We describe new findings relating to the role of the enzyme steroid sulfatase in maternal postpartum behavioural processes, and discuss how these point to a novel molecular risk pathway underlying postpartum mood disorders. Specifically, we suggest that aberrant steroid hormone-dependent regulation of neuronal calcium influx via extracellular matrix proteins and membrane receptors involved in responding to the cell's microenvironment might be important. Testing of this hypothesis might identify novel therapeutic targets and predictive biomarkers.

Neighbouring plants modify maize root foraging for phosphorus: coupling nutrients and neighbours for improved nutrient-use efficiency.

Nutrient distribution and neighbours can impact plant growth, but how neighbours shape root-foraging strategy for nutrients is unclear. Here, we explore new patterns of plant foraging for nutrients as affected by neighbours to improve nutrient acquisition. Maize (Zea mays) was grown alone (maize), or with maize (maize/maize) or faba bean (Vicia faba) (maize/faba bean) as a neighbour on one side and with or without a phosphorus (P)-rich zone on the other in a rhizo-box experiment. Maize demonstrated root avoidance in maize/maize, with reduced root growth in 'shared' soil, and increased growth away from its neighbours. Conversely, maize proliferated roots in the proximity of neighbouring faba bean roots that had greater P availability in the rhizosphere (as a result of citrate and acid phosphatase exudation) compared with maize roots. Maize proliferated more roots, but spent less time to reach, and grow out of, the P patches away from neighbours in the maize/maize than in the maize/faba bean experiment. Maize shoot biomass and P uptake were greater in the heterogeneous P treatment with maize/faba bean than with maize/maize system. The foraging strategy of maize roots is an integrated function of heterogeneous distribution of nutrients and neighbouring plants, thus improving nutrient acquisition and maize growth. Understanding the foraging patterns is critical for optimizing nutrient management in crops.

Elevated [CO2 ] alleviates the impacts of water deficit on xylem anatomy and hydraulic properties of maize stems.

Plants can modify xylem anatomy and hydraulic properties to adjust to water status. Elevated [CO2 ] can increase plant water potential via reduced stomatal conductance and water loss. This raises the question of whether elevated [CO2 ], which thus improves plant water status, will reduce the impacts of soil water deficit on xylem anatomy and hydraulic properties of plants. To analyse the impacts of water and [CO2 ] on maize stem xylem anatomy and hydraulic properties, we exposed potted maize plants to varying [CO2 ] levels (400, 700, 900, and 1,200 ppm) and water levels (full irrigation and deficit irrigation). Results showed that at current [CO2 ], vessel diameter, vessel roundness, stem cross-section area, specific hydraulic conductivity, and vulnerability to embolism decreased under deficit irrigation; yet, these impacts of deficit irrigation were reduced at elevated [CO2 ]. Across all treatments, midday stem water potential was tightly correlated with xylem traits and displayed similar responses. A distinct trade-off between efficiency and safety in stem xylem water transportation in response to water deficit was observed at current [CO2 ] but not observed at elevated [CO2 ]. The results of this study enhance our knowledge of plant hydraulic acclimation under future climate environments and provide insights into trade-offs in xylem structure and function.

Responses of water accumulation and solute metabolism in tomato fruit to water scarcity and implications for main fruit quality variables.

Fruit is important for human health, and applying deficit irrigation in fruit production is a strategy to regulate fruit quality and support environmental sustainability. Responses of different fruit quality variables to deficit irrigation have been widely documented, and much progress has been made in understanding the mechanisms of these responses. We review the effects of water shortage on fruit water accumulation considering water transport from the parent plant into the fruit determined by hydraulic properties of the pathway (including xylem water transport and transmembrane water transport regulated by aquaporins) and the driving force for water movement. We discuss water relations and solute metabolism that affect the main fruit quality variables (e.g. size, flavour, nutrition, and firmness) at the cellular level under water shortage. We also summarize the most recent advances in the understanding of responses of the main fruit quality variables to water shortage, considering the effects of variety, the severity of water deficit imposed, and the developmental stage of the fruit. We finally identify knowledge gaps and suggest avenues for future research. This review provides new insights into the stress physiology of fleshy fruit, which will be beneficial for the sustainable production of high-quality fruit under deficit irrigation.

Heart Failure Drug Modifies the Intrinsic Dynamics of the Pre-Power Stroke State of Cardiac Myosin.

Omecamtiv mecarbil (OM), currently investigated for the treatment of heart failure, is the first example of a new class of drugs (cardiac myotropes) that can modify muscle contractility by directly targeting sarcomeric proteins. Using atomistic molecular dynamics simulations, we show that the binding of OM to the pre-power stroke state of cardiac myosin inhibits the functional motions of the protein and potentially affects Pi release from the nucleotide binding site. We also show that the changes in myosin ATPase activity induced by a set of OM analogues can be predicted from their relative affinity to the pre-power stroke state compared to the near rigor one, indicating that conformational selectivity plays an important role in determining the activity of these compounds.

Versatile optical setup customized to verify the quality of spherical and aspheric intraocular lenses.

This paper proposes a customized and versatile optical setup to evaluate the optical performance of different commercially available intraocular lenses (IOLs). The setup was used to measure the wavefront error induced by different IOL models, verifying and analyzing the magnitude of low- and high-order aberrations induced by currently available IOLs. Independent analyses included non-toric spherical and aspheric IOLs from three different manufacturers. Three different dioptric powers were tested: 15, 20, and 25 D from each model. Dioptric power, induced cylinder, and spherical aberration were measured in each tested lens. All lenses had dioptric power within the tolerated margin of error. Induced cylinder was also within the current standards and clinically irrelevant. Spherical aberration varied according to the analyzed dioptric power and to the IOL model. We reported on the importance of the plane where the spherical aberration is reported, IOL or cornea. All analyzed IOLs were within current standards for the dioptric power and induced cylinder. Spherical IOLs had higher spherical aberration measured at the IOL plane.

Ozone pollution will compromise efforts to increase global wheat production.

Introduction of high-performing crop cultivars and crop/soil water management practices that increase the stomatal uptake of carbon dioxide and photosynthesis will be instrumental in realizing the United Nations Sustainable Development Goal (SDG) of achieving food security. To date, however, global assessments of how to increase crop yield have failed to consider the negative effects of tropospheric ozone, a gaseous pollutant that enters the leaf stomatal pores of plants along with carbon dioxide, and is increasing in concentration globally, particularly in rapidly developing countries. Earlier studies have simply estimated that the largest effects are in the areas with the highest ozone concentrations. Using a modelling method that accounts for the effects of soil moisture deficit and meteorological factors on the stomatal uptake of ozone, we show for the first time that ozone impacts on wheat yield are particularly large in humid rain-fed and irrigated areas of major wheat-producing countries (e.g. United States, France, India, China and Russia). Averaged over 2010-2012, we estimate that ozone reduces wheat yields by a mean 9.9% in the northern hemisphere and 6.2% in the southern hemisphere, corresponding to some 85 Tg (million tonnes) of lost grain. Total production losses in developing countries receiving Official Development Assistance are 50% higher than those in developed countries, potentially reducing the possibility of achieving UN SDG2. Crucially, our analysis shows that ozone could reduce the potential yield benefits of increasing irrigation usage in response to climate change because added irrigation increases the uptake and subsequent negative effects of the pollutant. We show that mitigation of air pollution in a changing climate could play a vital role in achieving the above-mentioned UN SDG, while also contributing to other SDGs related to human health and well-being, ecosystems and climate change.

Impact of CMOS Pixel and Electronic Circuitry in the Performance of a Hartmann-Shack Wavefront Sensor.

This work presents a numerical simulation of a Hartmann-Shack wavefront sensor (WFS) that assesses the impact of integrated electronic circuitry on the sensor performance, by evaluating a full detection chain encompassing wavefront sampling, photodetection, electronic circuitry and wavefront reconstruction. This platform links dedicated C algorithms for WFS to a SPICE circuit simulator for integrated electronics. The complete codes can be easily replaced in order to represent different detection or reconstruction methods, while the circuit simulator employs reliable models of either off-the-shelf circuit components or custom integrated circuit modules. The most relevant role of this platform is to enable the evaluation of the applicability and constraints of the focal plane of a given wavefront sensor prior to the actual fabrication of the detector chip. In this paper, we will present the simulation results for a Hartmann-Shack wavefront sensor with an orthogonal array of quad-cells (QC) integrated along with active-pixel (active-pixel sensor (APS)) circuitry and analog-to-digital converters (ADC) on a "complementary metal oxide semiconductor" (CMOS) process and deploying a modal wavefront reconstructor. This extended simulation capability for wavefront sensors enables the test and verification of different photosensitive and circuitry topologies for position-sensitive detectors combined with the simulation of sampling microlenses and reconstruction algorithms, with the goal of enhancing the accuracy in the prediction of the wavefront-sensor performance before a detector CMOS chip is actually fabricated.

Percutaneous Device Closure of Paravalvular Leak: Combined Experience From the United Kingdom and Ireland.

BACKGROUND: Paravalvular leak (PVL) occurs in 5% to 17% of patients following surgical valve replacement. Percutaneous device closure represents an alternative to repeat surgery. METHODS: All UK and Ireland centers undertaking percutaneous PVL closure submitted data to the UK PVL Registry. Data were analyzed for association with death and major adverse cardiovascular events (MACE) at follow-up. RESULTS: Three hundred eight PVL closure procedures were attempted in 259 patients in 20 centers (2004-2015). Patient age was 67±13 years; 28% were female. The main indications for closure were heart failure (80%) and hemolysis (16%). Devices were successfully implanted in 91% of patients, via radial (7%), femoral arterial (52%), femoral venous (33%), and apical (7%) approaches. Nineteen percent of patients required repeat procedures. The target valve was mitral (44%), aortic (48%), both (2%), pulmonic (0.4%), or transcatheter aortic valve replacement (5%). Preprocedural leak was severe (61%), moderate (34%), or mild (5.7%) and was multiple in 37%. PVL improved postprocedure (P<0.001) and was none (33.3%), mild (41.4%), moderate (18.6%), or severe (6.7%) at last follow-up. Mean New York Heart Association class improved from 2.7±0.8 preprocedure to 1.6±0.8 (P<0.001) after a median follow-up of 110 (7-452) days. Hospital mortality was 2.9% (elective), 6.8% (in-hospital urgent), and 50% (emergency) (P<0.001). MACE during follow-up included death (16%), valve surgery (6%), late device embolization (0.4%), and new hemolysis requiring transfusion (1.6%). Mitral PVL was associated with higher MACE (hazard ratio [HR], 1.83; P=0.011). Factors independently associated with death were the degree of persisting leak (HR, 2.87; P=0.037), New York Heart Association class (HR, 2.00; P=0.015) at follow-up and baseline creatinine (HR, 8.19; P=0.001). The only factor independently associated with MACE was the degree of persisting leak at follow-up (HR, 3.01; P=0.002). CONCLUSION: Percutaneous closure of PVL is an effective procedure that improves PVL severity and symptoms. Severity of persisting leak at follow-up is independently associated with both MACE and death. Percutaneous closure should be considered as an alternative to repeat surgery.

Phenotypic and genome-wide association analysis of spike ethylene in diverse wheat genotypes under heat stress.

The gaseous phytohormone ethylene plays an important role in spike development in wheat (Triticum aestivum). However, the genotypic variation and the genomic regions governing spike ethylene (SET) production in wheat under long-term heat stress remain unexplored. We investigated genotypic variation in the production of SET and its relationship with spike dry weight (SDW) in 130 diverse wheat elite lines and landraces under heat-stressed field conditions. We employed an Illumina iSelect 90K single nucleotide polymorphism (SNP) genotyping array to identify the genetic loci for SET and SDW through a genome-wide association study (GWAS) in a subset of the Wheat Association Mapping Initiative (WAMI) panel. The SET and SDW exhibited appreciable genotypic variation among wheat genotypes at the anthesis stage. There was a strong negative correlation between SET and SDW. The GWAS uncovered five and 32 significant SNPs for SET, and 22 and 142 significant SNPs for SDW, in glasshouse and field conditions, respectively. Some of these SNPs closely localized to the SNPs for plant height, suggesting close associations between plant height and spike-related traits. The phenotypic and genetic elucidation of SET and its relationship with SDW supports future efforts toward gene discovery and breeding wheat cultivars with reduced ethylene effects on yield under heat stress.

Applying 'drought' to potted plants by maintaining suboptimal soil moisture improves plant water relations.

Pot-based phenotyping of drought response sometimes maintains suboptimal soil water content by applying high-frequency deficit irrigation (HFDI). We examined the effect of this treatment on water and abscisic acid (ABA) relations of two species (Helianthus annuus and Populus nigra). Suboptimal soil water content was maintained by frequent irrigation, and compared with the effects of withholding water and with adequate irrigation. At the same average whole-pot soil moisture, frequent irrigation resulted in larger soil water content gradients, lower root and xylem ABA concentrations ([X-ABA]), along with higher transpiration rates or stomatal conductance, compared with plants from which water was withheld. [X-ABA] was not uniquely related to transpiration rate or stomatal conductance, as frequently irrigated plants showed partial stomatal closure compared with well-watered controls, without differing in [X-ABA] and, in H. annuus, [ABA]leaf. In two P. nigra genotypes differing in leaf area, the ratio between leaf area and root weight in the upper soil layer influenced the soil water content of this layer. Maintaining suboptimal soil water content alters water relations, which might become dependent on root distribution and leaf area, which influences soil water content gradients. Thus genotypic variation in 'drought tolerance' derived from phenotyping platforms must be carefully interpreted.

Stomatal and growth responses to hydraulic and chemical changes induced by progressive soil drying.

A better understanding of physiological responses of crops to drought stress is important for ensuring sustained crop productivity under climate change. Here, we studied the effect on 15-day-old maize (Zea mays L.) plants of a 6 d non-lethal period of soil drying [soil water potential (SWP) decreased from -0.20 MPa to -0.81 MPa]. Root growth was initially stimulated during drying (when SWP decreased from -0.31 MPa to -0.38 MPa, compared with -0.29 MPa in well-watered pots), followed by inhibition during Days 5-6 (SWP from -0.63 MPa to -0.81 MPa). Abscisic acid (ABA) in the root began to accumulate as the root water potential declined during Days 2-3. Leaf elongation was inhibited from Day 4 (SWP less than -0.51 MPa), just after leaf ABA content began to increase, but coinciding with a decline in leaf water potential. The stomatal conductance was restricted earlier in the younger leaf (fourth) (on Day 3) than in the older leaf (third). The ethylene content of leaves and roots decreased during drying, but after the respective increase in ABA contents. This work identified critical timing of hydraulic and chemical changes at the onset of soil drying, which can be important in initiating early stomatal and growth responses to drought.

Increased soil phosphorus availability induced by faba bean root exudation stimulates root growth and phosphorus uptake in neighbouring maize.

Root growth is influenced by soil nutrients and neighbouring plants, but how these two drivers affect root interactions and regulate plant growth dynamics is poorly understood. Here, interactions between the roots of maize (Zea mays) and faba bean (Vicia faba) are characterized. Maize was grown alone (maize) or with maize (maize/maize) or faba bean (maize/faba bean) as competitors under five levels of phosphorus (P) supply, and with homogeneous or heterogeneous P distribution. Maize had longer root length and greater shoot biomass and P content when grown with faba bean than with maize. At each P supply rate, faba bean had a smaller root system than maize but greater exudation of citrate and acid phosphatase, suggesting a greater capacity to mobilize P in the rhizosphere. Heterogeneous P availability enhanced the root-length density of maize but not faba bean. Maize root proliferation in the P-rich patches was associated with increased shoot P uptake. Increased P availability by localized P application or by the presence of faba bean exudation stimulated root morphological plasticity and increased shoot growth in maize in the maize/faba bean mixture, suggesting that root interactions of neighbouring plants can be modified by increased P availability.

How can we improve crop genotypes to increase stress resilience and productivity in a future climate? A new crop screening method based on productivity and resistance to abiotic stress.

The need to accelerate the selection of crop genotypes that are both resistant to and productive under abiotic stress is enhanced by global warming and the increase in demand for food by a growing world population. In this paper, we propose a new method for evaluation of wheat genotypes in terms of their resilience to stress and their production capacity. The method quantifies the components of a new index related to yield under abiotic stress based on previously developed stress indices, namely the stress susceptibility index, the stress tolerance index, the mean production index, the geometric mean production index, and the tolerance index, which were created originally to evaluate drought adaptation. The method, based on a scoring scale, offers simple and easy visualization and identification of resilient, productive and/or contrasting genotypes according to grain yield. This new selection method could help breeders and researchers by defining clear and strong criteria to identify genotypes with high resilience and high productivity and provide a clear visualization of contrasts in terms of grain yield production under stress. It is also expected that this methodology will reduce the time required for first selection and the number of first-selected genotypes for further evaluation by breeders and provide a basis for appropriate comparisons of genotypes that would help reveal the biology behind high stress productivity of crops.