Maturation proteins associated with desiccation tolerance in soybean

A set of proteins that accumulates late in embryogenesis (Lea proteins) has been hypothesized to have a role in protecting the mature seed against desiccation damage. A possible correlation between their presence and the desiccation tolerant state in soybean seeds (Glycine max L. Chippewa) was tested. Proteins that showed the same temporal pattern of expression as that reported for Lea proteins were identified in the axes of soybean. They were distinct from the known storage proteins and were resistant to heat coagulation. The level of these “maturation” proteins was closely correlated with desiccation tolerance both in the naturally developing and in the germinating seed: increasing at 44 days after flowering, when desiccation tolerance was achieved, and decreasing after 18 hours of imbibition, when desiccation tolerance was lost. During imbibition, 100 micromolar abscisic acid or Polyethylene glycol-6000 (−0.6 megapascals) delayed disappearance of the maturation proteins, loss of desiccation tolerance, and germination. During maturation, desiccation tolerance was prematurely induced when excised seeds were dried slowly but not when seeds were held for an equivalent time at high relative humidity. In contrast, maturation proteins were induced under both conditions. We conclude that maturation proteins may contribute to desiccation tolerance of soybean seeds, though they may not be sufficient to induce tolerance by themselves.     

Induction of alpha-amylase inhibitor synthesis in barley embryos and young seedlings by abscisic Acid and dehydration stress

An endogenous α-amylase inhibitor was found to be synthesized in embryos of developing barley grain (Hordeum vulgare cv Bonanza). Accumulation of this protein occurred late in development (stage IV), at the same time that endogenous abscisic acid (ABA) showed a large increase. The inhibitor could be induced up to 23-fold in isolated immature embryos (stage III) by culture in ABA. Precocious germination was also blocked in stage III embryos by ABA. Dehydration stress on the isolated immature embryos also induced higher levels of the inhibitor and ABA. An even greater response to dehydration stress was observed in young seedlings, where inhibitor content increased 20-fold and ABA increased 80-fold during water stress. The high degree of correlation between ABA and inhibitor contents in in situ embryos, dehydrated embryos and young seedlings, as well as the increase in inhibitor caused by exogenously applied ABA to isolated embryos, suggests that increased α-amylase inhibitor synthesis in response to dehydration stress is mediated by ABA.     

Changes in abscisic acid levels in embryo axes of Norway maple and sycamore seeds during maturation and dehydration

Changes in the abscisic acid (ABA) levels in embryo axes of seeds, belonging to the orthodox (Norway maple — Acer platanoides L.) and recalcitrant (sycamore — Acer pseudoplatanus L.) categories, were investigated throughout maturation using an ELISA (enzyme-linked immunosorbent assay) test. Concentration of ABA in embryo axes substantially differed depending on species and sampling date. ABA was always higher in Norway maple except at the end of seed maturation when ABA content was similar in both species. During maturation ABA decreased in both species but the decline was more marked in Norway maple than in sycamore (11 vs. 3 fold). These species also differed in the pattern of ABA changes, which in sycamore embryo axes was very regular, while in Norway maple a sharp decrease was recorded after acquisition by the seeds of tolerance to desiccation. Dehydration of embryo axes of Norway maple caused a further significant decrease of ABA level. In contrast, in dehydrated sycamore embryo axes ABA content did not decrease, but slightly increased. The role of ABA in desiccation tolerance and dormancy of Norway maple and sycamore seeds is discussed.     

Abscisic Acid Content and Effects During Dehydration of Detached Leaves of Desiccation Tolerant Plants

Borya nitida is an angiospcrm whose detached leaves developcomplete tolerance to dehydration when they are equilibratedto air of 96% r.h. This treatment causes leaves to yellow aschlorophyll is destroyed, and abscisic acid contents increaseseveral-fold. Exogenous ABA (at 0.038–0.38 mol m^–3)promoted desiccation tolerance (a) in leaves undergoing toleranceinduction at 96% r.h., (b) only slightly during rapid dryingat rates which are normally injurious, and (c) considerablyin turgid tissue treated with ABA 48 h before rapid drying. ABA content also increased with intense water stress in Myrothamnusflabellifolia, a desiccation tolerant angiosperm which, unlikeBorya, retains most of its chlorophyll when dehydrated. Preliminaryincubation in ABA of detached leaves of this ‘resurrectionplant’ also promoted survival during rapid drying. Theability of ABA to substitute for the normal induction periodsuggests that this hormone participates in the development ofdesiccation tolerance. Key words: Abscisic acid, ABA, Drought tolerance, Resurrection plant     

Optically pure abscisic Acid analogs-tools for relating germination inhibition and gene expression in wheat embryos

We report an examination of the structural requirements of the abscisic acid (ABA) recognition response in wheat dormant seed embryos using optically pure isomers of ABA analogs. These compounds include permutations to the ABA structure with either an acetylene or a trans bond at C-4 C-5, and either a single or double bond at the C-2′ C-3′ double bond. (R)-ABA and the three isomers with the same configuration at C-1′ as natural ABA were found to be effective germination inhibitors. The biologically active ABA analogs exhibited differential effects on ABA-responsive gene expression. All the ABA analogs that inhibited germination induced two ABA-responsive genes, wheat group 3 lea and dhn (rab). However, (R)-ABA and (S)-dihydroABA were less effective in inducing the ABA-responsive gene Em within the time that embryonic germination was inhibited.     

Intermolecular interactions and water structure in a condensed phase B-DNA crystal

By controlled dehydration, the unit cells of dodecamer DNA–drug crystals have been shrunk from 68 000 (normal state) to 60 000 (partially dehydrated intermediate state) to 51 000 ų (fully dehydrated state), beyond which no further solvent loss occurs. The total solvent content in the normal crystals is ~40% by volume, reducing to ~20% in the fully dehydrated phase. The 25% reduction in cell volume induced a dramatic enhancement in the resolution of the X-ray diffraction data (from 2.6 to beyond 1.5 Å). We have determined the structures of the normal, partially dehydrated and fully dehydrated crystals. Details of the ligand binding have been presented in the preceding article. The present paper describes the unique features of the structure of the fully dehydrated phase. This structure was refined with 9015 unique observed reflections to R = 14.9%, making it one of the most reliable models of B-form DNA available. The crystals exist as infinite polymeric networks, in which neighbouring dodecamer duplexes are crosslinked through phosphate oxygens via direct bonding to magnesium cations. The DNA is packed so tightly that there is essentially only a single layer of solvent between adjacent molecules. The details of the crystal packing, magnesium bridging, DNA hydration and DNA conformation are described and compared with other experimental evidence related to DNA condensation.     

Effect of inhibition of abscisic Acid accumulation on the spatial distribution of elongation in the primary root and mesocotyl of maize at low water potentials

Previous work showed that accumulation of endogenous abscisic acid (ABA) acts both to maintain primary root growth and inhibit shoot growth in maize seedlings at low water potentials (ψ_w) (IN Saab, RE Sharp, J Pritchard, GS Voetberg [1990] Plant Physiol 93: 1329-1336). In this study, we have characterized the growth responses of the primary root and mesocotyl of maize (Zea mays L. cv FR27 × FRMo 17) to manipulation of ABA levels at low ψ_w with a high degree of spatial resolution to provide the basis for studies of the mechanism(s) of ABA action. In seedlings growing at low ψ_w and treated with fluridone to inhibit carotenoid (and ABA) biosynthesis, ABA levels were decreased in all locations of the root and mesocotyl growing zones compared with untreated seedlings growing at the same ψ_w. In the root, low ψ_w (−1.6 megapascals) caused a shortening of the growing zone, as reported previously. The fluridone treatment was associated with severe inhibition of root elongation rate, which resulted from further shortening of the growing zone. In the mesocotyl, low ψ_w (−0.3 megapascal) also resulted in a shortened growing zone. In contrast with the primary root, however, fluridone treatment prevented most of the inhibition of elongation and the shortening of the growing zone. Final cell length measurements indicated that the responses of both root and mesocotyl elongation to ABA manipulation at low ψ_w involve large effects on cell expansion. Measurements of the relative changes in root and shoot water contents and dry weights after transplanting to a ψ_w of −0.3 megapascal showed that the maintenance of shoot elongation in fluridone-treated seedlings was not attributable to increased water or seed-reserve availability resulting from inhibition of root growth. The results suggest a developmental gradient in tissue responsiveness to endogenous ABA in both the root and mesocotyl growing zones. In the root, the capacity for ABA to protect cell expansion at low ψ_w appears to decrease with increasing distance from the apex. In the mesocotyl, in contrast, the accumulation of ABA at low ψ_w appears to become increasingly inhibitory to expansion as cells are displaced away from the meristematic region.     

Human Papillomavirus Infection and Vaccination: Awareness and Knowledge of HPV and Acceptability of HPV Vaccine among Mothers of Teenage Daughters in Weihai,Shandong, China

In preparation for the introduction of human papillomavirus (HPV) vaccine, we investigated awareness and knowledge of HPV/HPV vaccine and potential acceptability to HPV vaccine among mothers with a teenage daughter in Weihai, Shandong, China. A cross-sectional survey was conducted in 2013 with a sample of 1850 mothers who had a daughter (aged 9–17 years) attending primary, junior and senior high schools. In the final sample (N = 1578, response rate 85.30%), awareness of HPV was reported by 305 (19.32%) mothers. Awareness varied significantly by daughter’s age (P<0.01), mother’s education level (P<0.01), mother’s occupation (P<0.01), household income (P<0.01) and residence type (P<0.01). Knowledge about HPV/HPV vaccine was poor with a mean total score of 3.56 (SD = 2.40) out of a possible score of 13. Mothers with a higher education level reported higher levels of knowledge (P = 0.02). Slightly more than one-fourth (26.49%) of mothers expressed their potential acceptability of HPV vaccine for their daughters. Acceptability increased along with increased daughters’ age (P<0.01), household income (P<0.01) and knowledge level (P<0.01). House wives and unemployed mothers had the highest acceptability (P<0.01). The most common reasons for not accepting HPV vaccination were “My daughter is too young to have risk of cervical cancer (30.95%)”, “The vaccine has not been widely used, and the decision will be made after it is widely used (24.91%)”, “Worry about the safety of the vaccine (22.85%)”. Awareness and knowledge of HPV/HPV vaccines are poor and HPV vaccine acceptability is low among these Chinese mothers. These results may help inform appropriate health education programs in this population.     

Characterization of the Denitrification-Associated Phosphorus Uptake Properties of “Candidatus Accumulibacter phosphatis” Clades in Sludge Subjected to Enhanced Biological Phosphorus Removal

To characterize the denitrifying phosphorus (P) uptake properties of “Candidatus Accumulibacter phosphatis,” a sequencing batch reactor (SBR) was operated with acetate. The SBR operation was gradually acclimated from anaerobic-oxic (AO) to anaerobic-anoxic-oxic (A2O) conditions by stepwise increases of nitrate concentration and the anoxic time. The communities of “Ca. Accumulibacter” and associated bacteria at the initial (AO) and final (A2O) stages were compared using 16S rRNA and polyphosphate kinase genes and using fluorescence in situ hybridization (FISH). The acclimation process led to a clear shift in the relative abundances of recognized “Ca. Accumulibacter” subpopulations from clades IIA > IA > IIF to clades IIC > IA > IIF, as well as to increases in the abundance of other associated bacteria (Dechloromonas [from 1.2% to 19.2%] and “Candidatus Competibacter phosphatis” [from 16.4% to 20.0%]), while the overall “Ca. Accumulibacter” abundance decreased (from 55.1% to 29.2%). A series of batch experiments combined with FISH/microautoradiography (MAR) analyses was performed to characterize the denitrifying P uptake properties of the “Ca. Accumulibacter” clades. In FISH/MAR experiments using slightly diluted sludge (∼0.5 g/liter), all “Ca. Accumulibacter” clades successfully took up phosphorus in the presence of nitrate. However, the “Ca. Accumulibacter” clades showed no P uptake in the presence of nitrate when the sludge was highly diluted (∼0.005 g/liter); under these conditions, reduction of nitrate to nitrite did not occur, whereas P uptake by “Ca. Accumulibacter” clades occurred when nitrite was added. These results suggest that the “Ca. Accumulibacter” cells lack nitrate reduction capabilities and that P uptake by “Ca. Accumulibacter” is dependent upon nitrite generated by associated nitrate-reducing bacteria such as Dechloromonas and “Ca. Competibacter.”     

Quantitative models characterizing seed germination responses to abscisic Acid and osmoticum

Mathematical models were developed to characterize the physiological bases of the responses of tomato (Lycopersicon esculentum Mill. cv T5) seed germination to water potential (ψ) and abscisic acid (ABA). Using probit analysis, three parameters were derived that can describe the germination time courses of a seed population at different ψ or ABA levels. For the response of seed germination to reduced ψ, these parameters are the mean base water potential (¯ψ_b, MPa), the standard deviation of the base water potential among seeds in the population (σ_ψb, MPa), and the “hydrotime constant” (θ_H, MPa·h). For the response to ABA, they are the log of the mean base ABA concentration ([unk]ABA_b, m), the standard deviation of the base ABA concentration among seeds in the population (σ_ABAb, log[m]), and the “ABA-time constant” (θ_ABA, log[m]·h). The values of ¯ψ_b and [unk]ABA_b provide quantitative estimates of the mean sensitivity of germination rate to ψ or ABA, whereas σ^ψ_b and σ_ABAb account for the variation in sensitivity among seeds in the population. The time constants, θ_H and θ_ABA, indicate the extent to which germination rate will be affected by a given change in ψ or ABA. Using only these parameters, germination time courses can be predicted with reasonable accuracy at any medium ψ according to the equation probit(g) = [ψ - (θ_H/t_g) - ¯ψ_b]/σ_ψb, or at any ABA concentration according to the equation probit(g) = [log[ABA] - (θ_ABA/t_g) - log[[unk]ABA_b]]/σ_ABAb, where t_g is the time to radicle emergence of percentage g, and ABA is the ABA concentration (m) in the incubation solution. In the presence of both ABA and reduced ψ, the same parameters can be used to predict seed germination time courses based upon strictly additive effects of ψ and ABA in delaying the time of radicle emergence. Further analysis indicates that ABA and ψ can act both independently and interactively to influence physiological processes preparatory for radicle growth, such as the accumulation of osmotic solutes in the embryo. The models provide quantitative values for the sensitivity of germination to ABA or ψ, allow evaluation of independent and interactive effects of the two factors, and have implications for understanding how ABA and ψ may regulate growth and development.     

Accuracy of Inferior Vena Cava Ultrasound for Predicting Dehydration in Children with Acute Diarrhea in Resource-Limited Settings

Introduction

Although dehydration from diarrhea is a leading cause of morbidity and mortality in children under five, existing methods of assessing dehydration status in children have limited accuracy.

Objective

To assess the accuracy of point-of-care ultrasound measurement of the aorta-to-IVC ratio as a predictor of dehydration in children.

Methods

A prospective cohort study of children under five years with acute diarrhea was conducted in the rehydration unit of the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b). Ultrasound measurements of aorta-to-IVC ratio and dehydrated weight were obtained on patient arrival. Percent weight change was monitored during rehydration to classify children as having “some dehydration” with weight change 3–9% or “severe dehydration” with weight change > 9%. Logistic regression analysis and Receiver-Operator Characteristic (ROC) curves were used to evaluate the accuracy of aorta-to-IVC ratio as a predictor of dehydration severity.

Results

850 children were enrolled, of which 771 were included in the final analysis. Aorta to IVC ratio was a significant predictor of the percent dehydration in children with acute diarrhea, with each 1-point increase in the aorta to IVC ratio predicting a 1.1% increase in the percent dehydration of the child. However, the area under the ROC curve (0.60), sensitivity (67%), and specificity (49%), for predicting severe dehydration were all poor.

Conclusions

Point-of-care ultrasound of the aorta-to-IVC ratio was statistically associated with volume status, but was not accurate enough to be used as an independent screening tool for dehydration in children under five years presenting with acute diarrhea in a resource-limited setting.     

Water relation parameters of embryogenic cultures and seedlings of larch

Changes in the water relations parameters of developing somatic embryogenic and xygotic European larch (Larix decidua) were studied. Water release curves were generated by suspending tissue samples over unsaturated NaCl solutions until they reached vapor equilibration with the surrounding air. Twenty solutions were used whose water potentials ranged from −0.05 to −10 MPa. Water release curves were obtained by plotting paired values of tissue relative water content (RWC) and solution potential. Curves were derived for embryonic larch at various stages of development and for hypocotyls and roots from germinated zygotic and somatic embryos. The ability to resist dehydration increased markedly with development. Stage 1 tissue, which consisted of clusters of loosely associated nonchlorophyllous cells, had extremely low bulk elastic modulus (ε) (1.91 MPa) and apoplastic water content (A) (0.023), relatively high osmotic potential (Ψ_π) (−0.53 MPa), and lost turgor at 0.56 RWC. In contrast, mature embryoids with primary roots, hypocotyl, and cotyledons (stage 3) had an almost 4-fold increase in A (0.089), significantly higher ε (3.49 MPa), and lower Ψ_π (−0.88 MPa) and lost turgor at 0.66 RWC. Hypocotyl tissue from germinated somatic embryos lost turgor at 0.74 RWC and had higher ε, A, and solute accumulation than pregerminated tissue. Hypocotyl tissue resisted dehydration more strongly than root tissue, and differences between root and hypocotyl water relation parameters were more pronounced in xygotic than in somatic seedlings. Highest dehydration resistance was in zygotic hypocotyls. The characterization of the water relations of tissue cultures should allow the development of more consistent and reliable desiccation protocols to induce maturation of embryos and produce synchronously germinating seed.     

A new <Emphasis Type="Italic">Em</Emphasis>-like protein from <Emphasis Type="Italic">Lactuca sativa</Emphasis>, <Emphasis Type="Italic">LsEm1</Emphasis>, enhances drought and salt stress tolerance in <Emphasis Type="Italic">Escherichia coli</Emphasis> and rice

Late embryogenesis abundant (LEA) proteins are closely related to abiotic stress tolerance of plants. In the present study, we identified a novel Em-like gene from lettuce, termed LsEm1, which could be classified into group 1 LEA proteins, and shared high homology with Cynara cardunculus Em protein. The LsEm1 protein contained three different 20-mer conserved elements (C-element, N-element, and M-element) in the C-termini, N-termini, and middle-region, respectively. The LsEm1 mRNAs were accumulated in all examined tissues during the flowering and mature stages, with a little accumulation in the roots and leaves during the seedling stage. Furthermore, the LsEm1 gene was also expressed in response to salt, dehydration, abscisic acid (ABA), and cold stresses in young seedlings. The LsEm1 protein could effectively reduce damage to the lactate dehydrogenase (LDH) and protect LDH activity under desiccation and salt treatments. The Escherichia coli cells overexpressing the LsEm1 gene showed a growth advantage over the control under drought and salt stresses. Moreover, LsEm1-overexpressing rice seeds were relatively sensitive to exogenously applied ABA, suggesting that the LsEm1 gene might depend on an ABA signaling pathway in response to environmental stresses. The transgenic rice plants overexpressing the LsEm1 gene showed higher tolerance to drought and salt stresses than did wild-type (WT) plants on the basis of the germination performances, higher survival rates, higher chlorophyll content, more accumulation of soluble sugar, lower relative electrolyte leakage, and higher superoxide dismutase activity under stress conditions. The LsEm1-overexpressing rice lines also showed less yield loss compared with WT rice under stress conditions. Furthermore, the LsEm1 gene had a positive effect on the expression of the OsCDPK9, OsCDPK13, OsCDPK15, OsCDPK25, and rab21 (rab16a) genes in transgenic rice under drought and salt stress conditions, implying that overexpression of these genes may be involved in the enhanced drought and salt tolerance of transgenic rice. Thus, this work paves the way for improvement in tolerance of crops by genetic engineering breeding.     

Endogenous abscisic Acid in relation to bud growth in alternate bearing ;valencia' orange

An investigation was conducted into the relation of ABA (cis-trans-abscisic acid) in the dormant buds of alternate bearing `Valencia' orange (Citrus sinensis [L.] Osbeck) trees. ABA did not appear to be related to alternate bearing but t-ABA (2-transabscisic acid) did. There was 5- to 10-fold more t-ABA than ABA in the buds. There was more t-ABA in the buds of the “on” trees than in the buds of the “off” trees, and a drastic drop in t-ABA in both types of buds as spring growth approached. Bud dormancy and readiness for growth as related to t-ABA are discussed.     

State and Phase Transition Behaviors ofQuercus rubraSeed Axes and Cotyledonary Tissues: Relevance to the Desiccation Sensitivity and Cryopreservation of Recalcitrant Seeds

Freezing and melting transitions of cellular water in embryonic axes and cotyledonary tissues of recalcitrantQuercus rubra(red oak) seeds were compared under slow and rapid cooling conditions. The relevance of desiccation sensitivity (critical water content) and state/phase transition behaviors to cryopreservation was examined. Under a slow to intermediate cooling condition (≤10°C min⁻¹), unfrozen water content in the tissues decreased to less than the critical water content, resulting in a dehydration damage. Under a rapid cooling condition (>100°C min⁻¹) using liquid nitrogen (LN₂), freeze-induced dehydration damage could be avoided if the initial water content was >0.50 g g⁻¹dry wt. However, at water content >0.50 g g⁻¹dry wt, the vitrified cellular matrix was highly unstable upon warming at 10°C min⁻¹. These results offered a theoretical explanation on the difficulty for successful cryopreservation of recalcitrant red oak embryonic axes. A complete state/phase transition diagram for red oak axes was constructed, and a vitrification-based cryopreservation protocol that employed predehydration and rapid cooling was examined. State/phase transition behaviors of cellular water are important parameters for cryopreservation; however, vitrification alone was not sufficient for seed tissues to survive the cryopreservation condition.     

ROS production and antioxidative system activity in embryonic axes of <Emphasis Type="Italic">Quercus robur</Emphasis> seeds under different desiccation rate conditions

The seeds of pedunculate oak (Quercus robur L.) were subjected to slow (S) and rapid (R) desiccation at desiccation rates of 0.16 and 0.39% H₂O per hour, respectively. Till ca. 40% water content (WC) the germination capacity of seeds in the S and R variants was high (ca. 100%). Between 40 and 28% WC, germination capacity declined to 20 and 50% in S and R variants, respectively. The decrease in seed viability was accompanied by a significant increase of electrolyte leakage from embryonic axes (28% for S and 15% for R variants). In the embryonic axes of seeds subjected to slow desiccation, malondialdehyde (MDA) and free fatty acid (FFA) contents were significantly higher than those in R variants, indicating greater membrane damage due to lipid peroxidation. The production of ROS (H₂O₂ and O₂^·−) was significantly higher in S than in R variants. The low molecular weight antioxidants α-tocopherol, ascorbic acid (ASA), and phenolic compounds indicated different reactions in response to desiccation stress. ASA levels decreased during desiccation to a similar degree in both the S and R variants. A significant decrease of total phenols was observed in R variant, which coincided with a significant increase of guaiacol peroxidase (POX) activity. α-Tocopherol content was significantly higher in the embryonic axes of seeds subjected to rapid drying. The activities of the enzymatic scavengers APX and GR had similar runs and were slightly higher in R variant. The activities of POX and SOD were significantly higher in the embryonic axes of seeds subjected to rapid drying. These results show that rapid dehydration of Q. robur seeds leads to the greater mobilization of antioxidant system in embryonic axes, particularly increased levels of α-tocopherol and POX and SOD activities, in the first stages of water loss. This mobilization has a greater impact on maintenance of higher viability of seeds after drying to lower level of WC.     

Differences in cold and drought tolerance of high arctic and sub-arctic populations of Megaphorura arctica Tullberg 1876 (Onychiuridae: Collembola)

The springtail Megaphorura arctica (Onychiuridae: Collembola) inhabits the arctic and sub-arctic parts of the northern hemisphere where it on a seasonal basis will be exposed to severe cold and desiccating conditions. In the present study we compared how traits of stress resistance differed between two populations of M. arctica that were collected at a high arctic site (Spitsbergen) and a sub-arctic site (Akureyri, Iceland) with contrasting thermal environments. In addition we investigated how cold and desiccation affected the phospholipid fatty acid composition of M. arctica from Spitsbergen. The springtails from Spitsbergen were the most cold tolerant and this was linked to an almost three times higher level of trehalose accumulation during cryoprotective dehydration (15% and 5% of tissue dry weight in the Spitsbergen and Iceland populations, respectively). Although cryoprotective dehydration is intimately related to desiccation stress it was shown that M. arctica had a higher mortality when dehydrated over ice (−10 or −20 °C) than when dehydrated at temperatures above 1 °C. Thus, survival was lower after exposure to −10 °C than after exposure to a relative humidity of 91.2% RH at +1 °C although both treatments led to the same level of dehydration. Exposure to both cold (−10 and −20 °C) and desiccation at +1 °C caused significant changes in the phospholipid fatty acid composition with some similarities. These changes included a decrease in average chain length of the fatty acids due primarily to an increase in the phospholipid fatty acids 16:0 and a decrease in 18:3 and 20:4ω6.     

Novel Mitochondria-Targeted Heat-Soluble Proteins Identified in the Anhydrobiotic Tardigrade Improve Osmotic Tolerance of Human Cells

Tardigrades are able to tolerate almost complete dehydration through transition to a metabolically inactive state, called “anhydrobiosis”. Late Embryogenesis Abundant (LEA) proteins are heat-soluble proteins involved in the desiccation tolerance of many anhydrobiotic organisms. Tardigrades, Ramazzottius varieornatus, however, express predominantly tardigrade-unique heat-soluble proteins: CAHS (Cytoplasmic Abundant Heat Soluble) and SAHS (Secretory Abundant Heat Soluble) proteins, which are secreted or localized in most intracellular compartments, except the mitochondria. Although mitochondrial integrity is crucial to ensure cellular survival, protective molecules for mitochondria have remained elusive. Here, we identified two novel mitochondrial heat-soluble proteins, RvLEAM and MAHS (Mitochondrial Abundant Heat Soluble), as potent mitochondrial protectants from Ramazzottius varieornatus. RvLEAM is a group3 LEA protein and immunohistochemistry confirmed its mitochondrial localization in tardigrade cells. MAHS-green fluorescent protein fusion protein localized in human mitochondria and was heat-soluble in vitro, though no sequence similarity with other known proteins was found, and one region was conserved among tardigrades. Furthermore, we demonstrated that RvLEAM protein as well as MAHS protein improved the hyperosmotic tolerance of human cells. The findings of the present study revealed that tardigrade mitochondria contain at least two types of heat-soluble proteins that might have protective roles in water-deficient environments.