Environmental conditions modulate the effect of epigenetic factors controlling the response of Arabidopsis thaliana to Plasmodiophora brassicae.

The resistance of Arabidopsis thaliana to clubroot, a major disease of Brassicaceae caused by the obligate protist Plasmodiophora brassicae, is controlled in part by epigenetic factors. The detection of some of these epigenetic quantitative trait loci (QTLepi) has been shown to depend on experimental conditions. The aim of the present study was to assess whether and how temperature and/or soil water availability influenced both the detection and the extent of the effect of response QTLepi. The epigenetic recombinant inbred line (epiRIL) population, derived from the cross between ddm1-2 and Col-0 (partially resistant and susceptible to clubroot, respectively), was phenotyped for response to P. brassicae under four abiotic conditions including standard conditions, a 5°C temperature increase, drought, and flooding. The abiotic constraints tested had a significant impact on both the leaf growth of the epiRIL population and the outcome of the epiRIL-pathogen interaction. Linkage analysis led to the detection of a total of 31 QTLepi, 18 of which were specific to one abiotic condition and 13 common to at least two environments. EpiRIL showed significant plasticity under epigenetic control, which appeared to be specific to the traits evaluated and to the abiotic conditions. These results highlight that the environment can affect the epigenetic architecture of plant growth and immune responses and advance our understanding of the epigenetic factors underlying plasticity in response to climate change.

Growth kinetics, spatialization and quality of potato tubers monitored in situ by MRI - long-term effects of water stress.

Understanding the potato tuber development and effects of drought at key stages of sensitivity on yield is crucial, particularly when considering the increasing incidence of drought due to climate change. So far, few studies addressed the time course of tuber growth in soil, mainly due to difficulties in accessing underground plant organs in a non-destructive manner. This study aims to understand the tuber growth and quality and the complex long-term effects of realistic water stress on potato tuber yield. MRI was used to monitor the growth kinetics and spatialization of individual tubers in situ and the evolution of internal defects throughout the development period. The intermittent drought applied to plants reduced tuber yield by reducing tuber growth and increasing the number of aborted tubers. The reduction in the size of tubers depended on the vertical position of the tubers in the soil, indicating water exchanges between tubers and the mother plant during leaf dehydration events. The final size of tubers was linked with the growth rate at specific developmental periods. For plants experiencing stress, this corresponded to the days following rewatering, suggesting tuber growth plasticity. All internal defects occurred in large tubers and within a short time span immediately following a period of rapid growth of perimedullary tissues, probably due to high nutrient requirements. To conclude, the non-destructive 3D imaging by MRI allowed us to quantify and better understand the kinetics and spatialization of tuber growth and the appearance of internal defects under different soil water conditions.

Characterization of the Water Shortage Effects on Potato Tuber Tissues during Growth Using MRI Relaxometry and Biochemical Parameters.

The potato is one of the most cultivated crops worldwide, providing an important source of food. The quality of potato tubers relates to their size and dry matter composition and to the absence of physiological defects. It depends on the spatial and temporal coordination of growth and metabolic processes in the major tuber tissues: the cortex, flesh and pith. In the present study, variations in the biochemical traits of each of these tissues were investigated during tuber growth under optimal and water-deficit conditions. MRI relaxometry was used as a non-invasive and quantitative method to access information on cellular water status. The presence of slight but significant variations in organic compound contents quantified in the cortex and flesh revealed a tissue-dependent metabolic pattern. The T2 and relative I0 of the bi-exponential relaxation signal allowed a distinction to be made between the pith and the cortex, whereas the flesh could be differentiated from these tissues only through its relative I0. T2 values did not vary significantly during tuber development, in accordance with the typical growth pattern of tubers, but were shown to be sensitive to water stress. The interpretation of the multi-exponential transverse relaxation times is discussed and could be further developed via microscopic analysis.

Identification and Quantification of Glucosinolates and Phenolics in a Large Panel of Brassica napus Highlight Valuable Genetic Resources for Chemical Ecology and Breeding.

Glucosinolate (GLS) and phenolic contents in Brassicaceae contribute to biotic and abiotic stress responses. Breeding crop accessions harboring agroecologically relevant metabolic profiles require a characterization of the chemical diversity in Brassica germplasm. This work investigates the diversity of specialized metabolites in 281 accessions of B. napus. First, an LC-HRMS2-based approach allowed the annotation of 32 phenolics and 36 GLSs, revealing 13 branched and linear alkyl-GLSs and 4 isomers of hydroxyphenylalkyl-GLSs, many of which have been rarely reported in Brassica. Then, quantitative UPLC-UV-MS-based profiling was performed in leaves and roots for the whole panel. This revealed striking variations in the content of 1-methylpropyl-GLS (glucocochlearin) and a large variation of tetra- and penta-glucosyl kaempferol derivatives among accessions. It also highlighted two main chemotypes related to sinapoyl-O-hexoside and kaempferol-O-trihexoside contents. By offering an unprecedented overview of the phytochemical diversity in B. napus, this work provides a useful resource for chemical ecology and breeding.

Stress Biomarkers, Mood States, and Sleep during a Major Competition: "Success" and "Failure" Athlete's Profile of High-Level Swimmers.

The aim of this study was to evaluate stress markers, mood states, and sleep indicators in high-level swimmers during a major 7-days competition according to the outcomes. Nine swimmers [six men and three women (age: 22 ± 2 and 22 ± 4 years, respectively)] were examined. Before (PRE) and after (POST) each race (series, semi-finals, and finals), salivary concentrations of cortisol, α-amylase (sAA), and chromogranin-A (CgA) were determined. Mood states were assessed by the profile of mood state (POMS) questionnaire completed before and after the 7-days, and self-reported sleep diaries were completed daily. In the "failure" group, cortisol and sAA significantly increased between PRE-POST measurements (p < 0.05), while sCgA was not changed. Significant overall decrease of cortisol (-52.6%) and increase of sAA (+68.7%) was shown in the "failure group." In this group, fatigue, confusion and depression scores, and sleep duration before the finals increased. The results in the "success" group show tendencies for increased cortisol and sCgA concentrations in response to competition, while sAA was not changed. Cortisol levels before the semi-finals and finals and sCgA levels before the finals were positively correlated to the fatigue score in the "failure" group only (r = 0.89). sAA levels before and after the semi-finals were negatively correlated to sleep duration measured in the subsequent night (r = -0.90). In conclusion, the stress of the competition could trigger a negative mood profile and sleep disturbance which correspond to different responses of biomarkers related to the hypothalamo-pituitary-adrenal axis and the sympathetic nervous system (SNS) activity, cortisol, sAA, and CgA.

Acetylcholine chloride as a potential source of variability in the study of cutaneous vascular function in man.

INTRODUCTION: Laser-Doppler flowmetry (LDF) coupled with acetylcholine chloride (ACh) iontophoresis is increasingly recognized as a reliable non-invasive method to study the endothelial function. However, ACh-vasodilation measurement appears highly variable possibly due to the ACh pharmacological properties itself. These problems may be partially overcome by using methacholine chloride (MCh), a more stable synthetic agonist of muscarinic receptors, instead of ACh. Therefore, we first studied the correlation between the two drugs and then the effects of (1) spatial variability (inter-site measurements), (2) temporal variability (inter-day measurements), (3) intra-day variability (morning versus evening), and (4) age on the variability of both ACh-vasodilation and MCh-vasodilation. METHODS: The endothelium-dependent vasodilation response to simultaneous iontophoretic applications (4 doses of 10s at 0.1mA with 2min of current-free interval) of ACh (11mM) or MCh (10mM) was studied on the forearm of 40 healthy subjects (36 males, median 28yr, range 21-59yr). The percent change in perfusion (CVCpeak) from baseline and the area under the curve (CVC(AUC)) during iontophoresis were assessed. Inter-site, inter-day and intra-day coefficients of variation (CV) were studied for each drug as well as correlations between drugs and age. RESULTS: A linear relationship was found between ACh- and MCh-CVCpeak (r²=0.75, p=0.01) and between ACh- and MCh-CVC(AUC) (r²=0.55, p=0.02). MCh inter-site CV for both CVCpeak (12.2%) and CVC(AUC) (13.8%) was significantly lower than ACh inter-site CV for CVCpeak (15.5%) and CVC(AUC) (15.3%), respectively. MCh inter-day CV for CVCpeak (17.2%) and CVC(AUC) (14.6%) was significantly lower than ACh inter-day CV for CVCpeak (19.7%) and ACh CVC(AUC) (21.2%). For ACh and MCh, the CVCpeak and CVC(AUC) were higher at 16:00pm than at 11:00am (p<0.05 for all). Finally, both ACh- and MCh-CVCpeak exhibited a logarithmic decrease with age (r²=0.61, p<0.01 and r²=0.58, p<0.01). CONCLUSION: Although both drugs exhibited circadian and age variability, MCh exhibited less inter-site and interday variabilities than did ACh for the evaluation of cutaneous endothelium-dependent vasodilation. These findings should be taken into account in studies of cutaneous vascular function by iontophoresis coupled with laser Doppler flowmetry.

Effect of acute sleep deprivation on vascular function in healthy subjects.

Sleep disorders are associated with inflammation and sympathetic activation, which are suspected to induce endothelial dysfunction, a key factor in the increased risk of cardiovascular disease. Less is known about the early effects of acute sleep deprivation on vascular function. We evaluated microvascular reactivity and biological markers of endothelial activation during continuous 40 h of total sleep deprivation (TSD) in 12 healthy men (29 +/- 3 yr). The days before [day 1 (D1)] and during TSD (D3), at 1200 and 1800, endothelium-dependent and -independent cutaneous vascular conductance was assessed by iontophoresis of acetylcholine and sodium nitroprusside, respectively, coupled to laser-Doppler flowmetry. At 0900, 1200, 1500, and 1800, heart rate (HR) and instantaneous blood pressure (BP) were recorded in the supine position. At D1, D3, and the day after one night of sleep recovery (D4), markers of vascular endothelial cell activation, including soluble intercellular adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin, and interleukin-6 were measured from blood samples at 0800. Compared with D1, plasma levels of E-selectin were raised at D3, whereas intercellular adhesion molecule-1 and interleukin-6 were raised at D4 (P < 0.05). The endothelium-dependent and -independent CVC were significantly decreased after 29 h of TSD (P < 0.05). By contrast, HR, systolic BP, and the normalized low-frequency component of HR variability (0.04-0.15 Hz), a marker of the sympathetic activity, increased significantly within 32 h of TSD (P < 0.05). In conclusion, acute exposure to 40 h of TSD appears to cause vascular dysfunction before the increase in sympathetic activity and systolic BP.

Heart rate variability in novice pilots during and after a multi-leg cross-country flight.

BACKGROUND: A pilot's workload induces autonomic nervous system modulations which could be related to a decrease of vigilance that could impair safety. Kinetics during flight and recovery are not well known. OBJECTIVE: The aim of this study was to assess linear and nonlinear heart rate variability (HRV) modulations and vigilance during a high mental workload induced by a complex flight and subsequent recovery. METHODS: There were 10 novice pilots (37.8 +/- 4.4 yr, 115.8 +/- 15.7 h flight experience) who performed a 3 h 30 min (09:30-13:00) multi-leg cross-country flight (Piper Pa28 airplane: 160 hp). We recorded electrocardiogram (ECG) during the flight and performed tests during the 24 h before and after the flight (13:30, 16:00, 18:30, 21:00, and 06:45). Tests included a stand test (10 min supine, 10 min standing), a Mackworth 'clock' vigilance test, and a Karolinska Sleepiness Scale questionnaire. We assessed HRV components by time and frequency domains in parallel with the Poincaré plot analysis. RESULTS: The flight induced a progressive decrease of RR intervals, standard deviation between normal-to-normal intervals (SDNN), Poincaré SD1 and SD2 indices, and an increase of the low-frequency to high-frequency ratio (LF/HF). During recovery, vigilance remained depressed for 2 h 30 min after the flight. The decreased RR intervals and SD1 persisted for 5 h postflight both in supine and standing positions. LF/HF stayed elevated for 2 h 30 min after the flight. CONCLUSION: A multi-leg cross-country flight involves a vagal withdrawal and an increase of sympathetic activity lasting 5 h after landing. This delay could be recommended as a safety period.

Heart rate and autonomic balance during stand tests before and after fighter combat missions.

BACKGROUND: High workload during combat missions is a critical factor in the use of modern aircraft. Our objective was to evaluate the impact of piloting in war zones on the kinetics of the sympathovagal balance during recovery. METHODS: There were 40 military pilots who were monitored during operational flights in Afghanistan. Electrocardiographic activity was recorded during stand tests performed 1 h before takeoff (T-1), immediately after landing (L+0), 2 h after (L+2), and 4 h after (L+4) the flight. Missions were divided in two groups according to flight duration. RESULTS: The mean length of long flights was 4:31 +/- 0:53 h and of short flights 1:27 +/- 0:09 h. For long flights, at L+0, all indices related to parasympathetic modulation rose significantly in comparison to T-1, L+2, and L+4 (total power L+0: 2083 +/- 414 ms2 x Hz(-1),T-1: 1269 +/- 158 ms2 x Hz(-1), L+2: 1095 +/- 148 ms2 x Hz(-1), and L+4: 1238 +/- 124 ms2 x Hz(-1); high-frequency normalized units (HFnu) L+0: 16 +/- 2%, T-1: 11 +/- 1%, L+2: 10 +/- 1%, and L+4: 11 +/- 1%). At the same time the sympathetic frequency components significantly decreased (low-frequency normalized units (LFnu) L+0: 83 +/- 2%, T-1: 88 +/- 1%, L+2: 90 +/- 1%, and L+4: 89 +/- 1%; LF/HF L+0: 7 +/- 1, T-1: 11 +/- 1, L+2: 13 +/- 2, and L+4: 16 +/- 3). For short flights, the sympathetic components were higher at L+0 (LFnu: 77 +/- 2%; LF/HF: 14 +/- 3) than at T-1 (LFnu: 66 +/- 5%; LF/HF: 6 +/- 1). A concomitant reduction of vagal components was observed. CONCLUSIONS: Modulations of autonomic balance differed with the type of mission. A postflight sympathetic increase represents an autonomic adaptation due to stress and flight. A raise of parasympathetic modulation after flight may be related to the decrease of alertness.