Prevent Water Loss Research Articles

A small peptide modulates stomatal control via abscisic acid in long-distance signalling.

Mammalian peptide hormones propagate extracellular stimuli from sensing tissues to appropriate targets to achieve optimal growth maintenance 1 . In land plants, root-to-shoot signalling is important to prevent water loss by transpiration and to adapt to water-deficient conditions 2, 3 . The phytohormone abscisic acid has a role in the regulation of stomatal movement to prevent water loss 4 . However, no mobile signalling molecules have yet been identified that can trigger abscisic acid accumulation in leaves. Here we show that the CLAVATA3/EMBRYO-SURROUNDING REGION-RELATED 25 (CLE25) peptide transmits water-deficiency signals through vascular tissues in Arabidopsis, and affects abscisic acid biosynthesis and stomatal control of transpiration in association with BARELY ANY MERISTEM (BAM) receptors in leaves. The CLE25 gene is expressed in vascular tissues and enhanced in roots in response to dehydration stress. The root-derived CLE25 peptide moves from the roots to the leaves, where it induces stomatal closure by modulating abscisic acid accumulation and thereby enhances resistance to dehydration stress. BAM receptors are required for the CLE25 peptide-induced dehydration stress response in leaves, and the CLE25-BAM module therefore probably functions as one of the signalling molecules for long-distance signalling in the dehydration response.

The development of Speek/Pva/Teos blend membrane for proton exchange membrane fuel cells

Sulfonated poly ether ether ketone (SPEEK) has high potential for proton exchange membrane fuel cell (PEMFC) application and has been widely considered as most promising alternative to commercial membranes. In this study a novel ternary composite membrane consisting of SPEEK/poly (vinyl alcohol) (PVA) and tetraethyl ortosilicate (TEOS) were prepared by blending and casting method. The obtained samples were characterized by FT-IR, dynamic mechanical analysis (DMA), electrochemical impedance spectroscopy (EIS), oxidative and hydrolytic stability, water uptake capacity, swelling property and ion exchange capacity tests. According to these characterization test results, the addition of PVA in the membrane structure increased the mechanical strength and in addition TEOS is easily incorporated into the membrane structure because of the presence of modifiable groups in PVA. The addition of TEOS to blend membranes prevented water loss at high temperatures and TEOS addition indirectly increased the proton conductivity of the membranes. The highest performance of 600 mA/cm2 was obtained SP90/PV10/TE coded membrane at 0.6 V cell potential and fuel cell operate at 1 atm and 80 °C. At the same conditions Nafion 117 gave 400 mA/cm2. This study shows that blend membrane seems to be a promising alternative membrane for PEMFC application.

Technical and administrative feasibility of alluvial aquifer storage and recovery on the South Platte River of northeastern Colorado

Abstract Increasing population and climate change are causing water managers to reassess water storage. In this context, alluvial aquifer storage and recovery (ASR), in which excess water is stored in the alluvium near a river, offers a plausible option. To investigate this option, a coupled technical–administrative analysis was conducted to investigate the feasibility of alluvial ASR in the semi-arid US state of Colorado, where water rights are governed by the doctrine of prior appropriation. A hypothetical alluvial ASR facility near Brighton, Colorado with a storage capacity of 118,500 cubic meters (96 ac-ft) was considered. This analysis comprises both technical feasibility, using a groundwater model that explicitly accounts for clogging, and administrative feasibility, using a first-of-its-kind analysis of the legal availability of water including both free river and reusable effluent water. This coupled technical–administrative analysis suggests that alluvial ASR facilities present a viable option to meet rising demand for water storage, preventing water loss due to evaporation, reducing the effect of climate stress on water resources, and avoiding the need to purchase land for above-ground water storage facilities. More generally, this study illustrates the crucial importance of placing hydrologic analysis in the broader context of policy constraints.

Short-term high CO 2 treatment reduces water loss and decay by modulating defense proteins and organic osmolytes in Cardinal table grape after cold storage and shelf-life

Abstract Shelf-life quality was improved when Cardinal table grapes (Vitis vinifera L.) were pretreated with 20 kPa of CO2 for three days at the beginning of a long-term cold storage. This pretreatment was effective in avoiding postharvest losses of cv. Cardinal grapes in terms of water loss, oxidative damage and disease prevention. To elucidate those physiological and biochemical factors involved in preserving the postharvest shelf-life quality of table grapes, we studied the expression pattern of defense proteins such as pathogenesis-related proteins (PRs) and dehydrins, as well as the profile of protective osmolytes. The efficacy of a short-term high CO2 pretreatment in reducing fungal disease could be mediated by the increase in the low molecular mass chitinase isoform of 16 kDa, which is up-regulated in the skin of CO2-treated grapes in parallel with the shelf-life fungal decay control. In addition, the increasing accumulation of a 22 kDa dehydrin isoform and the endogenous levels of organic osmolytes proline and glycine betaine in fruit stored at 20 °C (mainly in CO2-treated fruit) revealed that these protective biomolecules might play a more effective role in maintaining the structural and cellular homeostasis of table grapes after the shelf-life period, helping to reduce water loss and membrane oxidative damage (malondialdehyde accumulation) associated with the senescence-related disorders of postharvest table grapes.

A \u2018NanoSuit\u2019 successfully protects petals of cherry blossoms in high vacuum: examination of living plants in an FE-SEM

Land plants have evolved on dry land and developed surface barriers to protect themselves from environmental stresses. We have previously reported that polymerization of a natural extracellular substance (ECS) on the outer surface of animals by electron beam or plasma irradiation, can give rise to a nano-scale layer, termed the “NanoSuit”, which can keep small animals alive under the high vacuum of a scanning electron microscope (SEM). In the present research, we have focused on plants, using petals of cherry blossoms, as experimental specimens and examined their behavior under high vacuum conditions. Experiments on healthy living petals have demonstrated that without any pre-treatment, the overall morphology of specimens is well preserved and intact after imaging in an SEM, suggesting that natural substances on the petal surface behave like animal ECS and form a NanoSuit following irradiation with an electron beam. Furthermore, we have shown that the surface material can be extracted with chloroform and polymerized into a free-standing membrane by plasma irradiation. From our results, we conclude that surface materials, which have the ability to prevent water loss under natural conditions, increase the barrier ability and can protect plants under high vacuum conditions.

Age-related mechanism and its relationship with secondary metabolism and abscisic acid in Aristotelia chilensis plants subjected to drought stress

Drought stress is the most important stress factor for plants, being the main cause of agricultural crop loss in the world. Plants have developed complex mechanisms for preventing water loss and oxidative stress such as synthesis of abscisic acid (ABA) and non-enzymatic antioxidant compounds such as anthocyanins, which might help plants to cope with abiotic stress as antioxidants and for scavenging reactive oxygen species. A. chilensis (Mol.) is a pioneer species, colonizing and growing on stressed and disturbed environments. In this research, an integrated analysis of secondary metabolism in Aristotelia chilensis was done to relate ABA effects on anthocyanins biosynthesis, by comparing between young and fully-expanded leaves under drought stress. Plants were subjected to drought stress for 20 days, and physiological, biochemical, and molecular analyses were performed. The relative growth rate and plant water status were reduced in stressed plants, with young leaves significantly more affected than fully-expanded leaves beginning from the 5th day of drought stress. A. chilensis plants increased their ABA and total anthocyanin content and showed upregulation of gene expression when they were subjected to severe drought (day 20), with these effects being higher in fully-expanded leaves. Multivariate analysis indicated a significant positive correlation between transcript levels for NCED1 (9-cis-epoxycarotenoid dioxygenase) and UFGT (UDP glucose: flavonoid-3-O-glucosyltransferase) with ABA and total anthocyanin, respectively. Thus, this research provides a more comprehensive analysis of the mechanisms that allow plants to cope with drought stress. This is highlighted by the differences between young and fully-expanded leaves, showing different sensibility to stress due to their ability to synthesize anthocyanins. In addition, this ability to synthesize different and high amounts of anthocyanins could be related to higher NCED1 and MYB expression and ABA levels, enhancing drought stress tolerance.

NUTRACEUTICAL VALUE OF EDIBLE FLOWERS UPON COLD STORAGE

The attraction and quality of edible flowers correlates with their high perishability. Few studies have evaluated whether edible flowers decay faster than they lose their nutraceutical value. In this experiment, ascorbic acid was negatively affected by cold storage in all the edible flowers investigated, whereas phenolic, flavonoid, and anthocyanin content were affected only in some cases. No decrease in total antioxidant activity was detected in any of the edible flowers at the end of their shelf life. Our dataset highlights that (i) the selection of edible flowers with low moisture content is key in ensuring a longer shelf life, and (ii) more effort should focus on preventing water loss in edible flowers.

Distinct physiological, biochemical and morphometric adjustments in the malaria vectors Anopheles gambiae and A. coluzzii as means to survive dry season conditions in Burkina Faso.

Aestivation and dispersive migration are the two strategies evoked in the literature to explain the way in which malaria vectors Anopheles coluzzii and A. gambiae survive the harsh climatic conditions of the dry season in sub-Saharan Africa. However, the physiological mechanisms regulating these two strategies are unknown. In the present study, mosquito species were exposed to controlled environmental conditions mimicking the rainy and dry seasons of south western Burkina Faso. Survival strategies were studied through morphometric (wing length), ecophysiological (respiratory gas exchanges), biochemical (cuticular hydrocarbons composition) and molecular (AKH mRNA expression levels) parameters, variations of which are usually considered to be hallmarks of aestivation and dispersion mechanisms in various insects. Our results showed that ecophysiological and morphometric adjustments are made in both species to prevent water losses during the dry season. However, the usual metabolic rate modifications expected as signatures of aestivation and migration were not observed, highlighting specific and original physiological mechanisms sustaining survival in malaria mosquitoes during the dry season. Differences in epicuticular hydrocarbon composition and AKH levels of expression were found between the permanent and temporary A. coluzzii populations, illustrating the great phenotypic plasticity of this mosquito species. Altogether, our work underlines the diverse and complex pattern of changes occurring in the two mosquito species and at the population level to cope with the dry season and highlights potential targets of future control tools.

黄土丘陵区小流域典型造林整地工程土壤水分特征曲线模拟

PDF HTML阅读 XML下载 导出引用 引用提醒 黄土丘陵区小流域典型造林整地工程土壤水分特征曲线模拟 DOI: 10.5846/stxb201801150108 作者: 作者单位: 中国水利水电科学研究院 流域水循环模拟与调控国家重点实验室 北京,中国科学院生态环境研究中心 城市与区域生态国家重点实验室 北京,中国科学院生态环境研究中心 城市与区域生态国家重点实验室 北京,中国科学院生态环境研究中心 城市与区域生态国家重点实验室 北京,中国科学院生态环境研究中心 城市与区域生态国家重点实验室 北京,中国科学院生态环境研究中心 城市与区域生态国家重点实验室 北京 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41501091，41371123）；中国科学院青年创新促进会项目；中国科协青年人才托举工程（2017-2019）项目；中国水科院基本科研业务费项目（SE0145C082017） Simulation of a soil water retention curve of typical soil and water conservation engineering measures in the Loess hilly watershed Author: Affiliation: State Key Laboratory of Simulation and Regulation of Water Cycle in River Basins,China Institute of Water Resources and Hydropower Research,Beijing,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-environmental Sciences,Chinese Academy of Sciences,Beijing,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-environmental Sciences,Chinese Academy of Sciences,Beijing,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-environmental Sciences,Chinese Academy of Sciences,Beijing,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-environmental Sciences,Chinese Academy of Sciences,Beijing,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-environmental Sciences,Chinese Academy of Sciences,Beijing Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:开展工程措施进行植被恢复是防治水土流失的有效方式。在黄土高原半干旱小流域，工程措施能够利用有限的降水资源，促进植被恢复。以甘肃定西龙滩小流域典型水土保持工程措施鱼鳞坑和反坡台为研究对象，采用配对实验设计，在实测土壤水分特征曲线基础上，分别利用Brooks-Corey、Gardner和van Genuchten模型对不同工程措施的土壤水分特征曲线进行模拟。研究结果发现：反坡台（10.63%）、鱼鳞坑（9.78%）粘粒含量显著高于对照样地（9.66%），粉粒含量反坡台（71.42%）与鱼鳞坑（70.74%）显著高于对照样地（67.85%）。较之对照样地，反坡台和鱼鳞坑饱和导水率分别提高53.5%和46.9%。3种模型均能够很好的拟合不同工程措施土壤水分特征曲线。较之对照，工程措施长期开展后，鱼鳞坑和反坡台的土壤有效水分分别提高15%和9%，且对表层土壤水分有效性的改善更为显著。 Abstract:Soil and water conservation engineering is an effective measure to prevent water loss. In the semi-arid watershed of the Loess Plateau, reasonable soil and water engineering development can utilize the limited precipitation, thus promoting vegetation restoration. In the current study, typical soil and water engineering (e.g., fish scale pits and adversely graded tableland) in a small watershed located in Dingxi City, Gansu Province were selected, and natural slope with the same vegetation served as a control. Soil samples at each site were collected from depths of 0-20, 20-40, 40-60, and 60-80 cm. Soil particle size distribution was analyzed. Soil water retention curves were monitored and simulated by Brooks-Corey, Gardner and van-Genuchten models. The results indicated that, the effects of soil and water conservation engineering on soil particle size distribution varied with soil depth. For the soil particle size distribution, the clay content of adversely graded tableland (10.63%) and fish scale pits (9.78%) was significantly higher than that of the control (9.66%). Meanwhile, the silt content of adversely graded tableland (71.42%) and fish scale pits (70.74%) also was significantly higher than that of the natural slope (67.85%). Compared with control, soil saturated hydraulic conductivity can be improved by 53.5% and 46.9% in the adversely graded tableland and fish scale pits, respectively. The Brooks-Corey, Gardner, and van Genuchten model can well fit the soil water retention curve of different soil and water engineering approaches. Compared with control, soil available water in adversely graded tableland and in fish scale pits can be increased by 15% and 9%, respectively. The effects of soil and water engineering on the soil available water in the surface soil layer were more pronounced after long-term implemention of soil and water engineering. 参考文献 相似文献 引证文献

Regulatory Gene Networks in Drought Stress Responses and Resistance in Plants.

Plant responses to drought stress have been analyzed extensively to reveal complex regulatory gene networks, including the detection of water deficit signals, as well as the physiological, cellular, and molecular responses. Plants recognize water deficit conditions at their roots and transmit this signal to their shoots to synthesize abscisic acid (ABA) in their leaves. ABA is a key phytohormone that regulates physiological and molecular responses to drought stress, such as stomatal closure, gene expression, and the accumulation of osmoprotectants and stress proteins. ABA transporters function as the first step for propagating synthesized ABA. To prevent water loss, ABA influx in guard cells is detected by several protein kinases, such as SnRK2s and MAPKs that regulate stomatal closure. ABA mediates a wide variety of gene expression machineries with stress-responsive transcription factors, including DREBs and AREBs, to acquire drought stress resistance in whole tissues. In this chapter, we summarize recent advances in drought stress signaling, focusing on gene networks in cellular and intercellular stress responses and drought resistance.

Protective effect of dietary Alchemilla mollis on UVB-irradiated premature skin aging through regulation of transcription factor NFATc1 and Nrf2/ARE pathways

BackgroundAlchemilla mollis (lady's mantle) is a common ingredient in skin care products. However, the protective mechanism of A. mollis against skin problems has not been elucidated. PurposeThis study was to investigate the effects of A. mollis ethanolic extract (AM) on UVB-irradiated normal human dermal fibroblasts (NHDF) and hairless mice. MethodsThe in vitro anti-photoaging effect of AM was performed in NHDFs. The antioxidant activities were assessed through DPPH, ABTS, and reactive oxygen species (ROS) assays. Matrix metalloproteinase 1 (MMP-1), IL-6, procollagen type I, and transforming growth factor-β1 (TGF-β1) were measured by kits. The protein levels of p-c-Jun, p-c-Fos, Nrf2, NQO-1, HO-1, nuclear NFATc1 and cytosolic p-NFATc1 were evaluated by western blotting. In in vivo, H&E and Masson's trichrome staining were carried out. Skin texture was analyzed using the roughness parameters. The expression of MMP-1, procollagen type I, TGF-β1 and elastin were measured by western blot. ResultsAM included gallic acid as an active constituent. AM exhibited a strong antioxidant effect by inhibiting DPPH and ABTS free radicals, as well as ROS production. It was also found to upregulate transforming growth factor β1, type I procollagen and elastin expression, and to downregulate matrix metalloproteinase-1 and interleukin-6 expression in AM-treated NHDFs under UVB irradiation. These effects were attributed to AP-1 and Nrf2/ARE signaling pathways. Significantly, it was demonstrated that AM regulated the UVB-induced NFATc1 dephosphorylation in nucleus. Based on dietary data, AM was effective for the prevention of wrinkle formation, skin thickening, water loss, and erythema in UVB-exposed mouse skin. ConclusionOur data indicate that A. mollis provides protection from UVB exposure in both hairless mice skin in vivo and NHDFs in vitro. AM might therefore be useful as a cosmetic material and functional food for the prevention of UVB-induced human skin photoaging.

A role for fruit structure in seed survival and germination of Swartzia langsdorffii Raddi beyond dispersal.

Diaspore structure has been hypothesised to play a role in seed viability and/or germination of recalcitrant seeds, especially for Swartzia langsdorffii. Thus, this work aims to (i) investigate the insitu contribution of pericarp and aril on seed viability and germination, and (ii) identify morphoanatomical traits of S.langsdorffii diaspores that allow its desiccation-sensitive seeds to remain viable. The role of the pericarp and aril in seed survival and germination was investigated by placing the whole fruit, whole seeds (arillate seed) and bare seeds (without aril) in soil in the forest understorey, assessing germination, emergence, dead, firm and predated seeds, and water content of pericarps, arils and seeds. Correlation analysis was performed between environmental variables and physiological parameters. Histochemical features of diaspores were also investigated. Pericarp water content fell after several months, while the aril maintained its water content. Seeds did not lose water even without the presence of the pericarp and aril. However, presence of the pericarp promoted seed water content, viability and germination long after dispersal. The embryo had a thickened outer periclinal cell wall. Pericarp and aril are not essential to prevent water loss in seeds, but do help to retain seed moisture, favouring viability maintenance and promoting germination during the rainy season. Morphoanatomical features of seeds are suggested as main factors that reduce water loss. Survival of these desiccation-sensitive seeds upon dispersal during the dry season appears to be facilitated by multiple diaspore features that prevent viability loss.

Eucalypt plants are physiologically and metabolically affected by infection with Ceratocystis fimbriata

Ceratocystis wilt, caused by Ceratocystis fimbriata, is currently one of the most important disease in eucalypt plantations. Plants infected by C. fimbriata have lower volumetric growth, lower pulp yields and reduced timber values. The physiological bases of infection induced by this pathogen in eucalypt plant are not known. Therefore, this study aims to assess the physiological and metabolic changes in eucalypt clones that are resistant and susceptible to C. fimbriata. Once, we evaluated in detail their leaf gas exchange, chlorophyll a fluorescence, water potential, metabolite profiling and growth-related parameters. When inoculated, the susceptible clone displayed reduced water potential, CO2 assimilation rate, stomatal conductance, transpiration rate, photochemical quenching coefficient, electron transport rate, and root biomass. Inoculated resistant and susceptible clones both presented higher respiration rates than healthy plants. Many compounds of primary and secondary metabolism were significantly altered after fungal infection in both clones. These results suggest that, C. fimbriata interferes in the primary and secondary metabolism of plants that may be linked to the induction of defense mechanisms and that, due to water restrictions caused by the fungus in susceptible plants, there is a partial closure of the stomata to prevent water loss and a consequent reduction in photosynthesis and the transpiration rate, which in turn, leads to a decrease in the plant's growth-related. These results combined, allowed for a better understanding of the physiological and metabolic changes following the infectious process of C. fimbriata, which limit eucalypt plant growth.

Photosynthetic gas exchange responses of Swietenia macrophylla King and Melia azedarach L. plantations under drought conditions

BackgroundThe environmental stresses caused by climate change have become more severe in recent decades, affecting tree growth and physiology. Tropical forests have great potential for global carbon sequestration. However, they suffer from heavy rainfall and prolonged dry periods due to climate change. Swietenia macrophylla King and Melia azedarach L. are economically valuable trees that are widely planted in southern Taiwan. Plantations are exposed to either prolonged dry periods or heavy rainfall within the seasons of tropical monsoon areas. Photo-physiological comparisons may provide information that can improve management of S. macrophylla and M. azedarach plantations in tropical regions.ResultsBoth species exhibited a midday depression in leaf photosynthesis regardless of the season. The net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) in the dry season all significantly decreased in both tree species. In addition, M. azedarach used water more efficiently than did S. macrophylla during the dry season, but S. macrophylla had higher PN compared with that in M. azedarach during the wet season. Temperature and vapor pressure deficit influenced PN variation in S. macrophylla and M. azedarach, respectively. Our data suggested that the PN and gs of M. azedarach, but not of S. macrophylla, were linearly correlated during the dry season. The reduction of the leaf area was more sever in M. azedarach than in S. macrophylla, thus preventing water loss more efficiently.ConclusionsM. azedarach adapted to drought by reducing total leaf area and maintaining higher PN, gs, E, and WUE compared with those measured in S. macrophylla during the dry season. M. azedarach is more drought adaptation and more suitable for both humid and semi-humid areas than S. macrophylla, whereas the latter should be limited to more humid areas.

Cellulose nanocrystals as reinforcements for collagen-based casings with low gas transmission

Cellulose nanocrystals (CNCs) of excellent mechanical properties, high purity, high aspect ratio, and cost-efficient production have drawn many attentions as a new class of reinforcement nanofillers. We chose CNCs as reinforcement nanofillers, which were incorporated in collagen to prepare CNCs/collagen casings by a traditional extruding method. The effects of CNCs on these casings were investigated. The dispersity and compatibility of CNCs within the collagen are rather good. The presence of CNCs can improve the light transmittance, barrier property, tensile strength, Young’s modulus, and thermostability of the CNCs/collagen casings, where collagen might cross-link with CNCs by electrostatic and hydrogen bonding interaction. When the CNCs content is 4 wt%, the water vapor permeability of CNCs/collagen casing reaches the minimum of 0.18 g·mm/h·m2·KPa. That concentration gave the highest light transmittance, and the mechanical properties were optimal. The development of CNCs/collagen casings represents an important potential to extend shelf life by the prevention of lipid oxidation and water loss of sausages.

Skin barrier and dry skin in the mature patient

Dry skin is the most common clinical manifestation of dermatologic diseases, and it presents with itching, redness, and desquamation—signs and clinical manifestations that are not only physically uncomfortable but also affect patients psychologically. The water content in the stratum corneum is largely dependent on the composition and amount of the intercellular lipids, which regulate the loss of water from the skin, and on the levels of hygroscopic substances of the natural moisturizing factors, which are responsible for retention of water in the stratum corneum. Prevention of water loss and penetration of potentially toxic substances and microorganisms into the body are the most important functions of the skin, which acts as a natural frontier between the inner organism and the environment. Skin barrier defects occur in several skin diseases, but the influence of aging on the skin barrier function is largely unknown and conflicting results have been reported. In this review, the structure and function of the barrier in relation to the aging process are discussed.

Elucidation of the Synthetic Mechanism of Acylceramide, an Essential Lipid for Skin Barrier Function.

The primary function of the skin is to act as a permeability barrier that prevents water loss from inside the body and external invasion such as by pathogens, harmful substances, and allergens. Lipids play a critical role in skin barrier formation by forming multi-lamellar structures in the stratum corneum, the outermost cell layer of the epidermis. Ceramide, the backbone of sphingolipids, accounts for more than 50% of the stratum corneum lipids. Acylceramides are epidermis-specific ceramide species essential for skin barrier formation. Decreases in acylceramide levels and changes in ceramide composition and chain-length are associated with such cutaneous disorders as ichthyosis, atopic dermatitis, and psoriasis. Acylceramide consists of a long-chain base and an amide-linked ultra-long-chain fatty acid (ULCFA, 28-36 carbon chain), which is ω-hydroxylated and esterified with linoleic acid. Although the molecular mechanism by which acylceramide is generated has not been fully understood for decades, we recently identified two genes, CYP4F22 and PNPLA1, involved in acylceramide synthesis and elucidated the entire biosynthetic pathway of acylceramide: the synthesis of ULCFA by ELOVL1 and ELOVL4, ω-hydroxylation of the ULCFA by CYP4F22, amide-bond formation with a long-chain base by CERS3, and transacylation of linoleic acid from triacylglycerol to ω-hydroxyceramide by PNPLA1 to generate acylceramide. CYP4F22 and PNPLA1 are the causative genes of ichthyosis. We demonstrated that mutations of CYP4F22 or PNPLA1 markedly reduced acylceramide production. Our recent findings provide important insights into the molecular mechanisms of skin barrier formation and of ichthyosis pathogenesis.

Drought-Enhanced Xylem Sap Sulfate Closes Stomata by Affecting ALMT12 and Guard Cell ABA Synthesis.

Water limitation of plants causes stomatal closure to prevent water loss by transpiration. For this purpose, progressing soil water deficit is communicated from roots to shoots. Abscisic acid (ABA) is the key signal in stress-induced stomatal closure, but ABA as an early xylem-delivered signal is still a matter of debate. In this study, poplar plants (Populus × canescens) were exposed to water stress to investigate xylem sap sulfate and ABA, stomatal conductance, and sulfate transporter (SULTR) expression. In addition, stomatal behavior and expression of ABA receptors, drought-responsive genes, transcription factors, and NCED3 were studied after feeding sulfate and ABA to detached poplar leaves and epidermal peels of Arabidopsis (Arabidopsis thaliana). The results show that increased xylem sap sulfate is achieved upon drought by reduced xylem unloading by PtaSULTR3;3a and PtaSULTR1;1, and by enhanced loading from parenchyma cells into the xylem via PtaALMT3b. Sulfate application caused stomatal closure in excised leaves and peeled epidermis. In the loss of sulfate-channel function mutant, Atalmt12, sulfate-triggered stomatal closure was impaired. The QUAC1/ALMT12 anion channel heterologous expressed in oocytes was gated open by extracellular sulfate. Sulfate up-regulated the expression of NCED3, a key step of ABA synthesis, in guard cells. In conclusion, xylem-derived sulfate seems to be a chemical signal of drought that induces stomatal closure via QUAC1/ALMT12 and/or guard cell ABA synthesis.

Permeability and microstructure of model stratum corneum lipid membranes containing ceramides with long (C16) and very long (C24) acyl chains

The Stratum corneum (SC) prevents water loss from the body and absorption of chemicals. SC intercellular spaces contain ceramides (Cer), free fatty acids (FFA), cholesterol (Chol) and cholesteryl sulfate (CholS). Cer with “very long” acyl chains (for example, N-lignoceroyl-sphingosine, CerNS24) are important for skin barrier function, whereas increased levels of “long” acyl Cer (for example, N-palmitoyl-sphingosine, CerNS16) occur in patients suffering from atopic eczema or psoriasis. We studied the impact of the replacement of CerNS24 by CerNS16 on the barrier properties and microstructure of model SC lipid membranes composed of Cer/FFA/Chol/CholS. Membranes containing the long CerNS16 were significantly more permeable to water (by 38–53%), theophylline (by 50–55%) and indomethacin (by 83–120%) than those containing the very long CerNS24 (either with lignoceric acid or a mixture of long to very long chain FFA). Langmuir monolayers with CerNS24 were more condensed than with CerNS16 and atomic force microscopy showed differences in domain formation. X-ray powder diffraction revealed that CerNS24-based membranes formed one lamellar phase and separated Chol, whereas the CerNS16-based membranes formed up to three phases and Chol. These results suggest that replacement of CerNS24 by CerNS16 has a direct negative impact on membrane structure and permeability.

Data-based modeling of drug penetration relates human skin barrier function to the interplay of diffusivity and free-energy profiles

Based on experimental concentration depth profiles of the antiinflammatory drug dexamethasone in human skin, we model the time-dependent drug penetration by the 1D general diffusion equation that accounts for spatial variations in the diffusivity and free energy. For this, we numerically invert the diffusion equation and thereby obtain the diffusivity and the free-energy profiles of the drug as a function of skin depth without further model assumptions. As the only input, drug concentration profiles derived from X-ray microscopy at three consecutive times are used. For dexamethasone, skin barrier function is shown to rely on the combination of a substantially reduced drug diffusivity in the stratum corneum (the outermost epidermal layer), dominant at short times, and a pronounced free-energy barrier at the transition from the epidermis to the dermis underneath, which determines the drug distribution in the long-time limit. Our modeling approach, which is generally applicable to all kinds of barriers and diffusors, allows us to disentangle diffusivity from free-energetic effects. Thereby we can predict short-time drug penetration, where experimental measurements are not feasible, as well as long-time permeation, where ex vivo samples deteriorate, and thus span the entire timescales of biological barrier functioning.