Association of Knowledge and Health Habits with Physiological Hydration Status.

The association of hydration knowledge and health habits with hydration status and fluid intake is rarely examined. We sought to determine whether knowledge or physical health behaviors predict physiological hydration status and fluid intake. Ninety-six participants (59 female; 27 ± 10 year) completed the previously validated hydration survey. Participants then recorded total fluids consumed (TFC), collected urine, and tracked void frequency for 24 h. Hydration status was assessed via 24 h urine specific gravity (USG) and osmolality (Uosm). Health behaviors included self-reported physical activity, BMI, smoking, alcoholic drinking, and sleep status. TFC was significantly correlated with 24 h USG (r = -0.390; p < 0.001), Uosm (r = -0.486; p < 0.001), total urine volume (r = 0.675; p < 0.001), and void frequency (r = 0.518; p < 0.001). Hydration knowledge was not correlated with 24 h USG (r = 0.085; p = 0.420), Uosm (r = 0.087; p = 0.419), urine total volume (r = 0.019; p = 0.857), void frequency (r = 0.030; p = 0.771), or TFC (r = 0.027; p = 0.813). Hydration knowledge did not predict 24 h USG (LR+ = 1.10; LR- = 0.90), Uosm (LR+ = 0.81; LR- = 1.35), or TFC (LR+ = 1.00; LR- = 1.00). Health habits did not predict 24 h USG, Uosm, or TFC. In conclusion, self-reported 24 h diet and fluid log recording is comparable to hydration status verification via 24 h urine collection. Hydration knowledge and health habits are not related to, or predictive of, hydration status.

Effects of preparticipating hypohydration on cardiac burden in recreational athletes.

The global temperature rise will have extensive consequences on our organ systems, but hypohydration caused by reduced water intake or increased water loss through sweating plays the most relevant role. Many studies have already demonstrated the association between hypohydration and impaired exercise performance, but data related to the cardiac burden of hypohydration are scarce. This study is a sub-investigation of our large, prospective, self-controlled trial on the effects of hypohydration on cardiopulmonary exercise capacity with previously published results. In the current sub-study, we analyzed the impact of hypohydration on cardiac burden in this cohort of fifty healthy, recreational athletes during cardiopulmonary exercise test.Therefore, each participant underwent cardiopulmonary exercise test with a standardized ramp protocol twice, once in hypohydrated state and once in euhydrated state as control, and the cardiac markers Troponin T, NT-pro-BNP and Chromogranin A were measured before and after the exercise test at each state. Mean age was 29.7 years and 34% of probands were female. Hypohydration led to a reduced body water, a significant decrease in oxygen uptake and lower levels of power output. Yet, Troponin T, NT-proBNP, Chromogranin A and lactate levels did not significantly differ between the two conditions.In this study cohort, decreased exercise capacity during hypohydration was more likely due to impaired cardiac output with diminished plasma volume rather than measurable cardiac stress from fluid deprivation. However, whether these data are generalizable to a diseased cohort is left unanswered and should be addressed in future randomized controlled trials.

Gluconeogenesis in frogs during cooling and dehydration exposure: new insights into tissue plasticity of the gluconeogenic pathway dependent on abiotic factors.

Anurans undergo significant physiological changes when exposed to environmental stressors such as low temperatures and humidity. Energy metabolism and substrate management play a crucial role in their survival success. Therefore, understanding the role of the gluconeogenic pathway and demonstrating its existence in amphibians is essential. In this study, we exposed the subtropical frog Boana pulchella to cooling (-2.5°C for 24 h) and dehydration conditions (40% of body water loss), followed by recovery (24 h), and assessed gluconeogenesis activity from alanine, lactate, glycerol and glutamine in the liver, muscle and kidney. We report for the first time that gluconeogenesis activity by 14C-alanine and 14C-lactate conversion to glucose occurs in the muscle tissue of frogs, and this tissue activity is influenced by environmental conditions. Against the control group, liver gluconeogenesis from 14C-lactate and 14C-glycerol was lower during cooling and recovery (P<0.01), and gluconeogenesis from 14C-glutamine in the kidneys was also lower during cooling (P<0.05). In dehydration exposure, gluconeogenesis from 14C-lactate in the liver was lower during recovery, and that from 14C-alanine in the muscle was lower during dehydration (P<0.05). Moreover, we observed that gluconeogenesis activity and substrate preference respond differently to cold and dehydration. These findings highlight tissue-specific plasticity dependent on the nature of the encountered stressor, offering valuable insights for future studies exploring this plasticity, elucidating the importance of the gluconeogenic pathway and characterizing it in anuran physiology.

The Cognitive Function and Taekwondo-Specific Kick Performance of Taekwondo Athletes at Different Hydration Statuses.

PURPOSE: Successful participation in taekwondo (TKD) requires athletes to possess quick decision-making abilities and demonstrate technical proficiency during competition. Dehydration, occurring during both training and competition, is widely recognized to have various negative effects. METHODS: This study investigated the impact of different levels of dehydration on cognitive function, as measured by the Vienna Test System, and the specific performance of kicking techniques among TKD athletes. Using a randomized crossover design, 12 participants were involved in the study. Before and after 1 hour of training at 80% of maximal heart rate, participants were weighed and provided urine samples. All participants were randomly assigned to 3 different hydration conditions: the euhydrated (EUH) group had unrestricted access to fluid consumption, while the hypohydrated (HYP) and severely HYP (S-HYP) groups experienced reductions of 2.0% and 4.0% of their initial body weight, respectively. RESULTS: The EUH group exhibited better reaction speed in reaction-time test-form S1 than the HYP and S-HYP groups. Notably, the EUH group demonstrated a significantly higher success rate in the front-side kick (EUH 98%, HYP 90%, S-HYP 88%; P < .05). However, the success rates of back roundhouse kick and free head kick were similar among the 3 statuses. Furthermore, postexercise heart rates were found to be significantly higher in the HYP and S-HYP groups compared with the EUH group. CONCLUSIONS: This study provides insight into the negative effects of dehydration on cognitive function and TKD-specific performance. It is recommended that TKD athletes maintain optimal hydration levels during training and competition to ensure optimal performance.

Water deprivation in poultry in connection with transport to slaughter-a review.

Poultry are deprived of water when transported to slaughter, beginning shortly prior to catching of the first bird and lasting through catching and loading, the journey on the vehicle, time spent in lairage, and up until time of death. Our aim was to review existing knowledge on variables which may be useful in determining the length of time that poultry may go without water in connection with transport before their welfare begins to deteriorate. During transport, it is likely that birds experience a motivation to drink, which may transition into the negative emotional state of thirst if water is unavailable. Determining when drinking motivation reaches a threshold where welfare is negatively impacted is challenging. In the absence of water, birds may over time experience dehydration which may be detected through physiological indicators as their body attempts to maintain homeostasis. In poultry, plasma osmolality, arginine vasotocin, and chloride have been suggested as being most suitable for assessing dehydration resulting from periods of water deprivation that correspond with typical transport durations, due to their particular sensitivity during this period. While initial dehydration may not be associated with negative emotional states, it is likely that it eventually leads to discomfort, but additional behavioral and motivational studies are necessary to infer when this begins. Impacts of thermal conditions, genetics, and the condition of the individual bird on the development of a dehydrated state were also assessed, though more information is needed to fully understand these interactions. With the available literature, this review concludes that total transport (i.e., from the initial deprivation from water until time of slaughter) durations of longer than 6 h are likely associated with measurable physiological indicators of dehydration and may potentially be associated with negative emotional states, although more research is needed to clarify this. Current available knowledge and assessment tools are not sufficient to detect the degradation of welfare derived from thirst itself, which should be further examined to protect poultry welfare during transport.

Terahertz imaging demonstrates its diagnostic potential and reveals a relationship between cutaneous dehydration and neuropathy for diabetic foot syndrome patients.

Diabetic foot syndrome, a long term consequence of Diabetes Mellitus, is the most common cause of non-traumatic amputations. Around 8% of the world population suffers from diabetes, 15% of diabetic patients present a diabetic foot ulcer which leads to amputation in 2.5% of the cases. There is no objective method for the early diagnosis and prevention of the syndrome and its consequences. We test terahertz imaging, which is capable of mapping the cutaneous hydration, for the evaluation of the diabetic foot deterioration as an early diagnostic test as well as ulcers prevention and tracking tool. Furthermore, the analysis of our terahertz measurements combined with neurological and vascular assessment of the patients indicates that the dehydration is mainly related to the peripheral neuropathy without a significant vascular cause.

Dehydration Status Aggravates Early Renal Impairment in Children: A Longitudinal Study.

Dehydration is common in children for physiological and behavioral reasons. The objective of this study was to assess changes in hydration status and renal impairment across school weekdays. We conducted a longitudinal study of three repeated measures of urinalysis within one week in November 2019 in a child cohort in Beijing, China. We measured urine specific gravity (USG) to determine the dehydration status, and the concentration of ß2-microglobulin (ß2-MG) and microalbumin (MA) to assess renal function impairment among 1885 children with a mean age of 7.7 years old. The prevalence of dehydration was 61.9%, which was significantly higher in boys (64.3%). Using chi-square tests and linear mixed-effects regression models, we documented the trends of the renal indicators' change over time among different hydration statuses. Compared to Mondays, there were apparent increases of ß2-MG concentrations on Wednesdays (ß = 0.029, p < 0.001) and Fridays (ß = 0.035, p < 0.001) in the dehydrated group, but not in the euhydrated group. As for the MA concentrations, only the decrease on Fridays (ß = -1.822, p = 0.01) was significant in the euhydrated group. An increased trend of elevated ß2-MG concentration was shown in both the euhydrated group (Z = -3.33, p < 0.001) and the dehydrated group (Z = -8.82, p < 0.001). By contrast, there was a decreased trend of elevated MA concentrations in the euhydrated group (Z = 3.59, p < 0.001) but not in the dehydrated group. A new indicator ratio, ß2-MG/MA, validated the consistent trends of renal function impairment in children with dehydration. Renal impairment trends worsened as a function of school days during the week and the dehydration status aggravated renal impairment during childhood across school weekdays, especially tubular abnormalities in children.

Screening of cowpea (Vigna unguiculata (L.) Walp.) genotypes for waterlogging tolerance using morpho-physiological traits at early growth stage.

The majority of cowpea (Vigna unguiculata (L.) Walp.) produced in the U.S. is planted shortly after the summer rains and subsequently depends on rain or artificial irrigation. Therefore, excessive precipitation and poor soil drainage will cause cowpea plants to suffer temporary waterlogging, reducing the submerged tissue's oxygen level. Although cowpea is sensitive to waterlogging, excessive moisture can induce several morpho-physiological changes with adverse impacts on yield in its early stages of development. The current study subjected 30 cowpea genotypes to 10-days of waterlogging at the seedling stage under a controlled environment. The dynamic changes of 24 morpho-physiological parameters under waterlogging and optimal water conditions were analyzed to understand cowpea's response to waterlogging. Significant waterlogging treatment, cowpea genotypes, and their interactions (P < 0.001) were observed for most of the measured parameters. The results indicated that plant height (PH), leaf area (LA), fresh (FW) and dry weight (DW) of cowpea genotypes were significantly decreased under waterlogging compared to the control treatments. Similar results were obtained for net photosynthesis (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration rate (E). However, the water use efficiency (WUE) and adventitious roots (ARs) increased linearly under waterlogging conditions. Waterlogging also declined chlorophyll fluorescence parameters except non-photochemical quenching (qN), which increased with excess soil moisture. In addition, waterlogging tolerance coefficient (WTC) and multivariate analysis (MCA) methods were used to characterize cowpea genotypes for waterlogging tolerance. Accordingly, the cowpea genotype Dagupan Pangasinan, UCR 369, and Negro were classified as waterlogging tolerant, while EpicSelect.4 and ICARDA 140071, as the most waterlogging sensitive. The cowpea genotypes and morpho-physiological traits determined from this study may be useful for genetic engineering and breeding programs that integrate cowpea waterlogging tolerance.

The potential of dynamic physiological traits in young tomato plants to predict field-yield performance.

To address the challenge of predicting tomato yields in the field, we used whole-plant functional phenotyping to evaluate water relations under well-irrigated and drought conditions. The genotypes tested are known to exhibit variability in their yields in wet and dry fields. The examined lines included two lines with recessive mutations that affect carotenoid biosynthesis, zeta z2083 and tangerine t3406, both isogenic to the processing tomato variety M82. The two mutant lines were reciprocally grafted onto M82, and multiple physiological characteristics were measured continuously, before, during and after drought treatment in the greenhouse. A comparative analysis of greenhouse and field yields showed that the whole-canopy stomatal conductance (gsc) in the morning and cumulative transpiration (CT) were strongly correlated with field measurements of total yield (TY: r2 = 0.9 and 0.77, respectively) and plant vegetative weight (PW: r2 = 0.6 and 0.94, respectively). Furthermore, the minimum CT during drought and the rate of recovery when irrigation was resumed were both found to predict resilience.

Zinc-finger protein MdBBX7/MdCOL9, a target of MdMIEL1 E3 ligase, confers drought tolerance in apple.

Water deficit is one of the main challenges for apple (Malus × domestica) growth and productivity. Breeding drought-tolerant cultivars depends on a thorough understanding of the drought responses of apple trees. Here, we identified the zinc-finger protein B-BOX 7/CONSTANS-LIKE 9 (MdBBX7/MdCOL9), which plays a positive role in apple drought tolerance. The overexpression of MdBBX7 enhanced drought tolerance, whereas knocking down MdBBX7 expression reduced it. Chromatin immunoprecipitation-sequencing (ChIP-seq) analysis identified one cis-element of MdBBX7, CCTTG, as well as its known binding motif, the T/G box. ChIP-seq and RNA-seq identified 1,197 direct targets of MdBBX7, including ETHYLENE RESPONSE FACTOR (ERF1), EARLY RESPONSIVE TO DEHYDRATION 15 (ERD15), and GOLDEN2-LIKE 1 (GLK1) and these were further verified by ChIP-qPCR and electronic mobility shift assays. Yeast two-hybrid screen identified an interacting protein of MdBBX7, RING-type E3 ligase MYB30-INTERACTING E3 LIGASE 1 (MIEL1). Further examination revealed that MdMIEL1 could mediate the ubiquitination and degradation of MdBBX7 by the 26S proteasome pathway. Genetic interaction analysis suggested that MdMIEL1 acts as an upstream factor of MdBBX7. In addition, MdMIEL1 was a negative regulator of the apple drought stress response. Taken together, our results illustrate the molecular mechanisms by which the MdMIEL1-MdBBX7 module influences the response of apple to drought stress.

Differential response of the photosynthetic machinery to dehydration in older and younger resurrection plants.

A group of vascular plants called homoiochlorophyllous resurrection plants evolved unique capabilities to protect their photosynthetic machinery against desiccation-induced damage. This study examined whether the ontogenetic status of the resurrection plant Craterostigma pumilum has an impact on how the plant responds to dehydration at the thylakoid membrane level to prepare cells for the desiccated state. Thus, younger plants (<4 months) were compared with their older (>6 months) counterparts. Ultrastructural analysis provided evidence that younger plants suppressed senescence-like programs that are realized in older plants. During dehydration, older plants degrade specific subunits of the photosynthetic apparatus such as the D1 subunit of PSII and subunits of the cytochrome b6f complex. The latter leads to a controlled down-regulation of linear electron transport. In contrast, younger plants increased photoprotective high-energy quenching mechanisms and maintained a high capability to replace damaged D1 subunits. It follows that depending on the ontogenetic state, either more degradation-based or more photoprotective mechanisms are employed during dehydration of Craterostigma pumilum.

The positive feedback regulatory loop of miR160-Auxin Response Factor 17-HYPONASTIC LEAVES 1 mediates drought tolerance in apple trees.

Drought stress tolerance is a complex trait regulated by multiple factors. Here, we demonstrate that the miRNA160-Auxin Response Factor 17 (ARF17)-HYPONASTIC LEAVES 1 module is crucial for apple (Malus domestica) drought tolerance. Using stable transgenic plants, we found that drought tolerance was improved by higher levels of Mdm-miR160 or MdHYL1 and by decreased levels of MdARF17, whereas reductions in MdHYL1 or increases in MdARF17 led to greater drought sensitivity. Further study revealed that modulation of drought tolerance was achieved through regulation of drought-responsive miRNA levels by MdARF17 and MdHYL1; MdARF17 interacted with MdHYL1 and bound to the promoter of MdHYL1. Genetic analysis further suggested that MdHYL1 is a direct downstream target of MdARF17. Importantly, MdARF17 and MdHYL1 regulated the abundance of Mdm-miR160. In addition, the Mdm-miR160-MdARF17-MdHYL1 module regulated adventitious root development. We also found that Mdm-miR160 can move from the scion to the rootstock in apple and tomato (Solanum lycopersicum), thereby improving root development and drought tolerance of the rootstock. Our study revealed the mechanisms by which the positive feedback loop of Mdm-miR160-MdARF17-MdHYL1 influences apple drought tolerance.

Overexpression of ZmPP2C55 positively enhances tolerance to drought stress in transgenic maize plants.

Serine/threonine protein phosphatases play essential roles in plants. PP2C has diverse functions related to development and stress response, while little is known about the functions of PP2C genes with respect to a variety of stresses in maize. In the present study, three ZmPP2C genes, ZmPP2C55, ZmPP2C28, and ZmPP2C71, were identified. Subcellular localization demonstrated that ZmPP2C28 and ZmPP2C71 were nuclear proteins, and ZmPP2C55 was located in both the nucleus and cytoplasm. qRT-PCR analysis showed that ZmPP2C55, ZmPP2C28, and ZmPP2C71 were expressed in roots, leaves and stems, and the three genes were responsive to drought, salt, high-temperature stress and exogenous ABA treatment. To explore the function of the ZmPP2C gene, ZmPP2C55-overexpressing transgenic lines were generated. The transgenic plants exhibited higher RWC, proline content, POD and SOD activities, GSH content and GSH/GSSG ratio and lower MDA content, electrolyte leakage and GSSG content compared with WT plants under natural stress treatment when seedlings were at the three-leaf. Our results illustrated that the overexpression of ZmPP2C55 positively enhanced tolerance to drought stress.

Transcription factors AcERF74/75 respond to waterlogging stress and trigger alcoholic fermentation-related genes in kiwifruit.

Kiwifruit plants have a fleshy, shallow root system which is sensitive to waterlogging stress, which results in a decrease in crop yield or even plants death. Although the waterlogging stress responses in kiwifruit have attracted much attention, the underlying molecular mechanism remains unclear. In this study, waterlogging led to drastic inhibition of root growth of 'Donghong' kiwifruit (Actinidia chinensis) plants grown in vitro, which was accompanied by significant elevation of endogenous acetaldehyde and ethanol contents. RNA-seq of roots of plants waterlogged for 0, 1 and 2 days revealed that a total of 149 genes were up- or down-regulated, including seven biosynthetic genes related to the glycolysis/gluconeogenesis pathway and 10 transcription factors. Analyses with real-time PCR, dual-luciferase assays and EMSA demonstrated that AcERF74 and AcERF75, two members of the ERF-VII subfamily, directly upregulated AcADH1 (alcohol dehydrogenase). Moreover, the overexpression of AcERF74/75 in transgenic calli resulted in dramatic increase of endogenous ethanol contents through the triggering of AcADH1 and AcADH2 expression. Although the AcPDC2 (pyruvate decarboxylase) expression was also enhanced in transgenic lines, the endogenous acetaldehyde contents showed no significant changes. These results illustrated that AcERF74/75 are two transcriptional activators on alcoholic fermentation related genes and are responsive to waterlogging stress in kiwifruit.

Awareness of Fluid Losses Does Not Impact Thirst during Exercise in the Heat: A Double-Blind, Cross-Over Study.

BACKGROUND: Thirst has been used as an indicator of dehydration; however, as a perception, we hypothesized that it could be affected by received information related to fluid losses. The purpose of this study was to identify whether awareness of water loss can impact thirst perception during exercise in the heat. METHODS: Eleven males participated in two sessions in random order, receiving true or false information about their fluid losses every 30 min. Thirst perception (TP), actual dehydration, stomach fullness, and heat perception were measured every 30 min during intermittent exercise until dehydrated by ~4% body mass (BM). Post exercise, they ingested water ad libitum for 30 min. RESULTS: Pre-exercise BM, TP, and hydration status were not different between sessions (p > 0.05). As dehydration progressed during exercise, TP increased significantly (p = 0.001), but it was the same for both sessions (p = 0.447). Post-exercise water ingestion was almost identical (p = 0.949) in the two sessions. CONCLUSION: In this study, thirst was a good indicator of fluid needs during exercise in the heat when no fluid was ingested, regardless of receiving true or false water loss information.

Impact of Repeated Acute Exposures to Low and Moderate Exercise-Induced Hypohydration on Physiological and Subjective Responses and Endurance Performance.

This study aimed to examine whether repeated exposures to low (2%) and moderate (4%) exercise-induced hypohydration may reverse the potentially deleterious effect of hypohydration on endurance performance. Using a randomized crossover protocol, ten volunteers (23 years, V˙O2max: 54 mL∙kg-1∙min-1) completed two 4-week training blocks interspersed by a 5-week washout period. During one block, participants replaced all fluid losses (EUH) while in the other they were fluid restricted (DEH). Participants completed three exercise sessions per week (walking/running, 55% V˙O2max, 40 °C): (1) 1 h while fluid restricted or drinking ad libitum, (2) until 2 and (3) 4% of body mass has been lost or replaced. During the first and the fourth week of each training block, participants completed a 12 min time-trial immediately after 2% and 4% body mass loss has been reached. Exercise duration and distance completed (14.1 ± 2.7 vs. 6.9 ± 1.5 km) during the fixed-intensity exercise bouts were greater in the 4 compared to the 2% condition (p < 0.01) with no difference between DEH and EUH. During the first week, heart rate, rectal temperature and perceived exertion were higher (p < 0.05) with DEH than EUH, and training did not change these outcomes. Exercise-induced hypohydration of 2% and 4% body mass impaired time-trial performance in a practical manner both at the start and end of the training block. In conclusion, exercise-induced hypohydration of 2% and 4% body mass impairs 12 min walking/running time-trial, and repeated exposures to these hypohydration levels cannot reverse the impairment in performance.

BaDBL1, a unique DREB gene from desiccation tolerant moss Bryum argenteum, confers osmotic and salt stress tolerances in transgenic Arabidopsis.

The dehydration-responsive element-binding (DREB) transcription factors play important roles in regulation of plant responses to abiotic stresses, however, few DREBs have been isolated from a desiccation tolerance moss, and the role of DREBs in the DT mechanism is still unknown. We have functionally characterized a unique DREB transcription factor BaDBL1 from the DT moss Bryum argenteum. Expression pattern analysis revealed that BaDBL1 was induced by dehydration-rehydration, salt, cold, and abscisic acid treatments. BaDBL1 was localized in the nucleus and had a transactivation region in its C-terminal region. Overexpression of BaDBL1 in Arabidopsis resulted in significantly increased osmotic and salt stress tolerance, as illustrated by higher fresh weight and antioxidase activities (SOD, POD and CAT) compared with WT under osmotic and salt stresses. Moreover, the transcription of stress-responsive genes, such as AtRD29A and AtCOR15A, AtLEA in BaDBL1-overexpressing lines were significantly up-regulated under osmotic and salt stresses compared with WT. Transcriptomic analysis revealed that BaDBL1-overexpression affected the lignin biosynthesis pathway by improving lignin content and regulating lignin-biosynthesis-related genes under osmotic stress. The results suggest that BaDBL1 may regulate plant tolerance to stress by enhancing anti-oxidase activities, regulating expression of stress-related genes and effecting the lignin biosynthesis, making BaDBL1 a candidate gene for stress tolerance improvement in crops.

The miR169n-NF-YA8 regulation module involved in drought resistance in Brassica napus L.

As an ancient and conserved plant microRNA (miRNA) family, miR169 targets nuclear factor Y subunit alpha (NF-YA) family members. The miR169-NF-YA module is associated with plant development and various stress responses. However, the function of miR169 in response to drought stress in rapeseed (Brassica napus L.) is unclear. In the present study, we showed that miR169n acted as a negative regulator of drought resistance in rapeseed by targeting a nuclear factor Y-A gene, NF-YA8. miR169n was strongly down-regulated by drought stress. Expression of a miR169n target mimicry construct (MIM169n) which functioned as a sponge to trap miR169n resulted in enhanced resistance of transgenic plants to both osmotic stress at the post-germination stage and drought stress at the seedling stage. MIM169n plants had a higher relative water content (RWC) and proline content, lower relative electrolyte leakage (REL), and showed higher antioxidative capability compared with those of control (CK) plants under drought stress. Moreover, NF-YA8 was verified as a target of miR169n, and overexpression of NF-YA8 led to improved tolerance of rapeseed to osmotic stress at the post-germination stage. Overall, our findings implied that the miR169n-NF-YA8 regulatory module could serve as a potential target for genetic improvement of drought resistance in B. napus.

Overexpression of the tyrosine decarboxylase gene MdTyDC in apple enhances long-term moderate drought tolerance and WUE.

Drought stress affects the apple yield and quality. Tyrosine decarboxylase (TyDC) plays a fundamental role in many secondary metabolite reactions in higher plants (including those involving dopamine). Our aims of this study are: 1) to identify the role of TyDC in dopamine derivative biosynthesis and its function in long-term moderate drought conditions; and 2) to explore the role of MdTyDC in plant growth and development as well as the drought stress response. Wild type and three independently apple plants overexpression of MdTyDC were treated for long-term moderate drought stress. The growth and physiological parameters of apple plant, photosynthetic capacity, antioxidant enzymes activity, water use efficiency (WUE), stomatal behavior, amino acid content and dopamine content were detected under long-term moderate drought stress. Overexpression of MdTyDC (OE) in apple showed better growth performance, higher photosynthetic capacity and higher capacity for photochemical reactions than wild type lines (WT). Under long-term moderate drought stress, OE lines showed higher WUE, increased ABA content, decreased stomatal aperture, higher antioxidant activity, lower accumulation of ROS and increases in amino acids, such as proline, phenylalanine and lysine. In addition, qRT-PCR revealed higher gene expression of MdTyDC and dopamine content in OE compared with WT lines under long-term moderate drought stress. These results indicate that MdTyDC confers long-term moderate drought tolerance by improving photosynthetic capacity, WUE, antioxidant activity, dopamine content and changing the contents of amino acids (such as proline accumulation).