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.     

The Role of Anorexia in Resistance and Tolerance to Infections in Drosophila

Most infections induce anorexia but its function, if any, remains unclear. Because this response is common among animals, we hypothesized that infection-induced diet restriction might be an adaptive trait that modulates the host's ability to fight infection. Two defense strategies protect hosts against infections: resistance, which is the ability to control pathogen levels, and tolerance, which helps the host endure infection-induced pathology. Here we show that infected fruit flies become anorexic and that diet restriction alters defenses, increasing the fly's tolerance to Salmonella typhimurium infections while decreasing resistance to Listeria monocytogenes. This suggests that attempts to extend lifespan through diet restriction or the manipulation of pathways mimicking this process will have complicated effects on a host's ability to fight infections.     

Acid Tolerance of Biofilm Cells of Streptococcus mutans

Streptococcus mutans, a member of the dental plaque community, has been shown to be involved in the carious process. Cells of S. mutans induce an acid tolerance response (ATR) when exposed to sublethal pH values that enhances their survival at a lower pH. Mature biofilm cells are more resistant to acid stress than planktonic cells. We were interested in studying the acid tolerance and ATR-inducing ability of newly adhered biofilm cells of S. mutans. All experiments were carried out using flow-cell systems, with acid tolerance tested by exposing 3-h biofilm cells to pH 3.0 for 2 h and counting the number of survivors by plating on blood agar. Acid adaptability experiments were conducted by exposing biofilm cells to pH 5.5 for 3 h and then lowering the pH to 3.5 for 30 min. The viability of the cells was assessed by staining the cells with LIVE/DEAD BacLight viability stain. Three-hour biofilm cells of three different strains of S. mutans were between 820- and 70,000-fold more acid tolerant than corresponding planktonic cells. These strains also induced an ATR that enhanced the viability at pH 3.5. The presence of fluoride (0.5 M) inhibited the induction of an ATR, with 77% fewer viable cells at pH 3.5 as a consequence. Our data suggest that adhesion to a surface is an important step in the development of acid tolerance in biofilm cells and that different strains of S. mutans possess different degrees of acid tolerance and ability to induce an ATR.     

Dendritic Cells from Oral Cavity Induce Foxp3+ Regulatory T Cells upon Antigen Stimulation

Evidence is accumulating that dendritic cells (DCs) from the intestines have the capacity to induce Foxp3⁺CD4⁺ regulatory T cells (T-regs) and regulate immunity versus tolerance in the intestines. However, the contribution of DCs to controlling immunity versus tolerance in the oral cavity has not been addressed. Here, we report that DCs from the oral cavity induce Foxp3⁺ T-regs as well as DCs from intestine. We found that oral-cavity-draining cervical lymph nodes contained higher frequencies of Foxp3⁺ T-regs and ROR-γt⁺ CD4⁺T cells than other lymph nodes. The high frequency of Foxp3⁺ T-regs in the oral-cavity-draining cervical lymph nodes was not dependent on the Toll like receptor (TLR) adaptor molecules, Myd88 and TICAM-1 (TRIF). In contrast, the high frequency of ROR-γt⁺ CD4⁺T cells relies on Myd88 and TICAM-1. In vitro data showed that CD11c⁺ DCs from oral-cavity-draining cervical lymph nodes have the capacity to induce Foxp3⁺ T-regs in the presence of antigen. These data suggest that, as well as in the intestinal environment, antigen-presenting DCs may play a vital role in maintaining tolerance by inducing Foxp3⁺ T-regs in the oral cavity.     

Relationship of cold acclimation,total phenolic content and antioxidant capacity with chilling tolerance in petunia (Petunia × hybrida)

Extracts from Petunia × hybrida plants, which had been subjected to cold pretreatment to induce chilling tolerance, were analyzed for specific phenolic acids, such as gentisic acid, and assessed for their antioxidant capacity by their ability to reduce (decolorize) the 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt radical (ABTS^*). Gentisic acid was induced in significant quantities by the third week of cold acclimation and levels remained constant up to the fourth week. Cold acclimation induced accumulation of total phenolics, which was positively related to antioxidant capacity. Petunia plants recovered from chilling injury following 3 weeks of cold pretreatment with an increase in total phenolics, which suggested some form of antioxidant protection. However, antioxidant capacity was only moderately related to chilling tolerance, which indicated that factors other than total phenolics may play a role in the chilling tolerance in petunia. These data suggest that the 5 °C cold pretreatment may have initially caused injury that impeded acclimation at the outset, and that subsequent phenolic metabolism was related to protective functions in petunia.     

The acid adaptive tolerance response in Campylobacter jejuni induces a global response,as suggested by proteomics and microarrays

Campylobacter jejuni CI 120 is a natural isolate obtained during poultry processing and has the ability to induce an acid tolerance response (ATR) to acid + aerobic conditions in early stationary phase. Other strains tested they did not induce an ATR or they induced it in exponential phase. Campylobacter spp. do not contain the genes that encode the global stationary phase stress response mechanism. Therefore, the aim of this study was to identify genes that are involved in the C. jejuni CI 120 early stationary phase ATR, as it seems to be expressing a novel mechanism of stress tolerance. Two-dimensional gel electrophoresis was used to examine the expression profile of cytosolic proteins during the C. jejuni CI 120 adaptation to acid + aerobic stress and microarrays to determine the genes that participate in the ATR. The results indicate induction of a global response that activated a number of stress responses, including several genes encoding surface components and genes involved with iron uptake. The findings of this study provide new insights into stress tolerance of C. jejuni, contribute to a better knowledge of the physiology of this bacterium and highlight the diversity among different strains.     

The Involvement of Wheat F-Box Protein Gene TaFBA1 in the Oxidative Stress Tolerance of Plants

As one of the largest gene families, F-box domain proteins have been found to play important roles in abiotic stress responses via the ubiquitin pathway. TaFBA1 encodes a homologous F-box protein contained in E3 ubiquitin ligases. In our previous study, we found that the overexpression of TaFBA1 enhanced drought tolerance in transgenic plants. To investigate the mechanisms involved, in this study, we investigated the tolerance of the transgenic plants to oxidative stress. Methyl viologen was used to induce oxidative stress conditions. Real-time PCR and western blot analysis revealed that TaFBA1 expression was up-regulated by oxidative stress treatments. Under oxidative stress conditions, the transgenic tobacco plants showed a higher germination rate, higher root length and less growth inhibition than wild type (WT). The enhanced oxidative stress tolerance of the transgenic plants was also indicated by lower reactive oxygen species (ROS) accumulation, malondialdehyde (MDA) content and cell membrane damage under oxidative stress compared with WT. Higher activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POD), were observed in the transgenic plants than those in WT, which may be related to the upregulated expression of some antioxidant genes via the overexpression of TaFBA1. In others, some stress responsive elements were found in the promoter region of TaFBA1, and TaFBA1 was located in the nucleus, cytoplasm and plasma membrane. These results suggest that TaFBA1 plays an important role in the oxidative stress tolerance of plants. This is important for understanding the functions of F-box proteins in plants’ tolerance to multiple stress conditions.     

Induction of “Low Dose” Tolerance to a Bacterial Somatic Antigen in Neonatal Mice

THE concept of “low dose” tolerance rests on the observation that specific immunological unresponsiveness can be induced by extremely small doses of antigen, sometimes in quantities too small to provoke antibody formation as such^1–3. The initial observations were made with soluble serum proteins, which are generally not considered “strong” antigens^4,5. Low dose tolerance can be induced also to the highly immunogenic protein antigen derived from Salmonella flagella, as assessed at the level of serum antibody^6,7. Furthermore, recent studies at the level of antibody forming cells indicate that immunological tolerance to complex antigens such as sheep erythrocytes and bacterial extracts, as well as to serum proteins or chemical haptens, can be induced in neonatal or adult animals^9–14. In this regard, relatively large doses of antigen are reportedly necessary to induce tolerance in adult rodents to a bacterial antigen such as Escherichia coli lipopolysaccharide (LPS). For example, 10–15 mg of the LPS is necessary to induce tolerance, as measured by an indirect haemolytic plaque assay with antigen coated sheep erythrocytes^15,16. Lower doses of LPS reportedly induce only immunity.     

Transgenerational Adaptation of Arabidopsis to Stress Requires DNA Methylation and the Function of Dicer-Like Proteins

Epigenetic states and certain environmental responses in mammals and seed plants can persist in the next sexual generation. These transgenerational effects have potential adaptative significance as well as medical and agronomic ramifications. Recent evidence suggests that some abiotic and biotic stress responses of plants are transgenerational. For example, viral infection of tobacco plants and exposure of Arabidopsis thaliana plants to UVC and flagellin can induce transgenerational increases in homologous recombination frequency (HRF). Here we show that exposure of Arabidopsis plants to stresses, including salt, UVC, cold, heat and flood, resulted in a higher HRF, increased global genome methylation, and higher tolerance to stress in the untreated progeny. This transgenerational effect did not, however, persist in successive generations. Treatment of the progeny of stressed plants with 5-azacytidine was shown to decrease global genomic methylation and enhance stress tolerance. Dicer-like (DCL) 2 and DCL3 encode Dicer activities important for small RNA-dependent gene silencing. Stress-induced HRF and DNA methylation were impaired in dcl2 and dcl3 deficiency mutants, while in dcl2 mutants, only stress-induced stress tolerance was impaired. Our results are consistent with the hypothesis that stress-induced transgenerational responses in Arabidopsis depend on altered DNA methylation and smRNA silencing pathways.     

Cryoprotective dehydration is widespread in Arctic springtails

Cryoprotective dehydration (CPD) is a cold tolerance strategy employed by small invertebrates that readily lose water by evaporation when subjected to sub-zero temperatures in the presence of ice. Until now, relatively few species have been investigated using methods by which CPD can be shown. In the present study we investigated the cold tolerance strategy of seven soil arthropod species from the high Arctic Spitzbergen, and compared water content and water loss, body fluid melting points (MP) and survival under cold and desiccating conditions. We tested the hypothesis that CPD is a commonly occurring cold hardiness strategy among soil arthropods. We found that four springtail species (Hypogastrura viatica, Folsomia quadrioculata, Oligaphorura groenlandica and Megaphorura arctica; Collembola) went through severe dehydration and MP equilibration with ambient temperature, and thus overwinter by employing CPD, whereas a beetle (Atheta graminicola) and one of the springtails (Isotoma anglicana) were typical freeze avoiding species over-wintering by supercooling. Desiccation tolerance of the red velvet mite (Neomolgus littoralis) was also investigated; very low water loss rates of this species indicated that it does not survive winter by use of CPD. All in all, the results of the present study confirm the hypothesis that CPD is an effective over-wintering strategy which is widespread within soil arthropods.     

The Effect of Abscisic Acid on the Freezing Tolerance of Callus Cultures of Lotus corniculatus L

The effects of growth temperature (2°C and 24°C), abscisic acid (ABA) concentration, duration of exposure to ABA, and light were assessed for their ability to induce acclimation to freezing temperatures in callus cultures of Lotus corniculatus L. cv Leo, a perennial forage legume. The maximal expression of freezing tolerance was achieved on B₅ media containing 10⁻⁵ molar ABA, at 24°C for 7 or 14 days. Under these culture conditions, the freezing tolerance of the callus approximated that observed in field grown plants. In contrast, low temperatures (2°C) induced only a limited degree of freezing tolerance in these cultures. Viability was assessed by tetrazolium reduction and by regrowth of the callus. The two assays often differed in their estimates of absolute freezing tolerance. Regression analysis of the temperature profile suggested that there may be two or more distinct populations of cells differing in freezing tolerance, which may have contributed to the variability between viability assays.     

Reproductive colonization of land by frogs: Embryos and larvae excrete urea to avoid ammonia toxicity

Vertebrate colonization of land has occurred multiple times, including over 50 origins of terrestrial eggs in frogs. Some environmental factors and phenotypic responses that facilitated these transitions are known, but responses to water constraints and risk of ammonia toxicity during early development are poorly understood. We tested if ammonia accumulation and dehydration risk induce a shift from ammonia to urea excretion during early stages of four anurans, from three origins of terrestrial development. We quantified ammonia and urea concentrations during early development on land, under well‐hydrated and dry conditions. Where we found urea excretion, we tested for a plastic increase under dry conditions and with ammonia accumulation in developmental environments. We assessed the potential adaptive role of urea excretion by comparing ammonia tolerance measured in 96h‐LC₅₀ tests with ammonia levels in developmental environments. Ammonia accumulated in foam nests and perivitelline fluid, increasing over development and reaching higher concentrations under dry conditions. All four species showed high ammonia tolerance, compared to fishes and aquatic‐breeding frogs. Both nest‐dwelling larvae of Leptodactylus fragilis and late embryos of Hyalinobatrachium fleischmanni excreted urea, showing a plastic increase under dry conditions. These two species can develop the longest on land and urea excretion appears adaptive, preventing their exposure to potentially lethal levels of ammonia. Neither late embryos of Agalychnis callidryas nor nest‐dwelling larvae of Engystomops pustulosus experienced toxic ammonia levels under dry conditions, and neither excreted urea. Our results suggest that an early onset of urea excretion, its increase under dry conditions, and elevated ammonia tolerance can all help prevent ammonia toxicity during terrestrial development. High ammonia represents a general risk for development which may be exacerbated as climate change increases dehydration risk for terrestrial‐breeding frogs. It may also be a cue that elicits adaptive physiological responses during early development.     

Ascaris suum: electrophoretic characterization of reproductive tract and perienteric fluid polypeptides, and effects of seminal and uterine fluids on spermiogenesis.

Fluids isolated from the testis, seminal vesicle, uterus, and pseudocoelomic cavity of Ascaris suum were characterized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and measured for protein concentration, pH, and osmolarity. The testis and seminal fluids display much homology and share major polypeptide components having molecular weights of 15,000 and 35,000. A cytoplasmic extract of spermatids from the seminal vesicle exhibited a banding pattern nearly identical to that of testis fluid. The seminal fluid has unique major components of 57,000 and 150,000, and seminal fluid from individual worms showed differences in major band concentration and distribution of minor components. The uterine fluid has major polypeptides of 14,000, 16,000, 66,000, 74,000, 120,000, and 140,000, and exhibits more similarity to the perienteric fluid then either the seminal or testis fluids. Electrophoretic comparisons of four uterine regions revealed nearly identical banding patterns although somewhat higher concentrations of four major components occurred in certain segments. The male and female perienteric fluids have major bands at 40,000, 120,000, and 140,000, and the female fluid has more intense minor components of 90,000 and 115,000. Perienteric fluid from individual worms differed only in minor band distribution. The reproductive fluids have numerous minor components mostly from 20,000 to 70,000, while the perienteric fluid minor bands are mainly located in the 80,000 to 120,000 range. The pH of the seminal fluid (6.5) differs from that of the uterine fluid (7.7), and both seminal and uterine fluids are of lower osmolarity than the perienteric fluid. In vitro studies demonstrate that uterine fluid does not induce spermatid transformation into bipolar, ameboid spermatozoa, while the seminal fluid induces only lipid granule coalescence in either seminal vesicle or terminal testis spermatids.     

Survey of Extreme Solvent Tolerance in Gram-Positive Cocci: Membrane Fatty Acid Changes in Staphylococcus haemolyticus Grown in Toluene

We exploited the unique ecological niche of oil fly larval guts to isolate a strain of Staphylococcus haemolyticus which may be the most solvent-tolerant gram-positive bacterium yet described. This organism is able to tolerate 100% toluene, benzene, and p-xylene on plate overlays and saturating levels of these solvents in monophasic liquid cultures. A comparison of membrane fatty acids by gas chromatography after growth in liquid media with and without toluene showed that in cells continuously exposed to solvent the proportion of anteiso fatty acids increased from 25.8 to 33.7% while the proportion of 20:0 straight-chain fatty acids decreased from 19.3 to 10.1%. No changes in the membrane phospholipid composition were noted. Thus, S. haemolyticus alters its membrane fluidity via fatty acid composition to become more fluid when it is exposed to solvent. This response is opposite that commonly found in gram-negative bacteria, which change their fatty acids so that the cytoplasmic membrane is less fluid. Extreme solvent tolerance in S. haemolyticus is not accompanied by abnormal resistance to anionic or cationic detergents. Finally, six strains of Staphylococcus aureus and five strains of Staphylococcus epidermidis, which were not obtained by solvent selection, also exhibited exceptional solvent tolerance.     

Hsp70 Induction and hsp70 Gene polymorphisms as Indicators of acclimatization under hyperthermic conditions

The possibility of using Hsp70 and hsp70 gene polymorphisms as markers of acclimatization was investigated. Volunteers (22) were subjected to an acclimatization regimen and blood analysed for Hsp70 (Hsp72) and hsp70 polymorphisms before and after a heat tolerance test. Physiological parameters denoting acclimatization, or not, were correlated to levels of Hsp70 and combination of hsp70 genes. Only individuals that acclimatized had decreased basal Hsp70 levels and increased ability to induce Hsp70 together with a specific hsp70 genotype combination. We propose that Hsp70 levels (basal vs. induced) with the genotype combination have the potential to be used as markers of acclimatization.