Expression of fatty-acid-modifying enzymes in the halotolerant black yeast Aureobasidium pullulans (de Bary) G. Arnaud under salt stress

Multiple tolerance to stressful environmental conditions of the black, yeast-like fungus Aureobasidium pullulans is achieved through different adaptations, among which there is the restructuring of the lipid composition of their membranes. Here, we describe three novel genes encoding fatty-acid-modifying enzymes in A. pullulans, along with the levels of their mRNAs under different salinity conditions. High levels of Δ ⁹−desaturase and Δ¹²−desaturase mRNAs were seen at high salinities, which were consistent with an increased desaturation of the fatty acids in the cell membranes. Elevated levels of elongase mRNA were also detected. Surprisingly, increases in the levels of these mRNAs were also seen following hypo-osmotic shock, while hyperosmotic shock had exactly the opposite effect, demonstrating that data that are obtained from up-shift and down-shift salinity studies should be interpreted with caution.     

Comparison of seed germination and early seedling growth responses to salinity and temperature of the halophyte Chloris virgata and the glycophyte Digitaria sanguinalis

Salinization is an increasing land degradation issue in the Songnen Grassland of northern China. Effects of salinity and temperature on seed germination and seedling growth of Chloris virgata, a promising halophyte, and Digitaria sanguinalis, a widespread glycophyte were examined in six soil solutions (0, 50, 100, 150, 200 and 250 mm NaCl) and four temperatures (15, 20, 25 and 30°C). Germination percentages and rates of both species decreased significantly at higher salinities, but ungerminated seeds can recover germination upon supply of distilled water. Radicle length, seedling height and the total dry weight of both species generally decreased in a concentration‐dependent manner at 20°C and above as the salinity increased. However, at 15°C, the salt‐treated seedlings showed decreases with a similar magnitude for different salinities. Low salinities seem to stimulate germination and seedling growth of C. virgata compared with the control treatment. Both species were more sensitive to salinity during the seedling stage than the germination stage. Digitaria sanguinalis from the saline Songnen Grassland region seems to develop a halophyte‐like adaptive strategy to some extent. However, C. virgata may still dominate most hyperhaline areas due to its higher salt tolerance.     

Longevity and growth of <Emphasis Type="Italic">Acacia tortilis</Emphasis>; insights from <Superscript>14</Superscript>C content and anatomy of wood

Background  

Acacia tortilis is a keystone species across arid ecosystems in Africa and the Middle East. Yet, its life-history, longevity and growth are poorly known, and consequently ongoing changes in tree populations cannot be managed in an appropriate manner. In other arid areas parenchymatic bands marking growth zones in the wood have made dendrochronological studies possible. The possibilities for using pre- and post-bomb ¹⁴C content in wood samples along with the presence of narrow marginal parenchymatic bands in the wood is therefore tested to gain further insight into the age, growth and growth conditions of A. tortilis in the hyper-arid Eastern Desert of Egypt.     

Identification by In Vitro Translation and Northern Blot Analysis of Heat Shock mRNAs Isolated from Wheat Seeds Exposed to Different Temperatures During Ripening

Poly(A)⁺RNA isolated from durum and common wheat seeds exposed to different thermal regimes during ripening, was translated in vitro using a rabbit reticulocyte system. The modification of protein synthesis was studied with particular regard to the heat shock proteins produced under high temperature conditions. One-dimensional polyacrylamide gel electrophoresis analysis showed products ranging in size from 14 to 100 kDa, some of which were present only when mRNA samples from high temperature-treated plants were translated. The mRNAs were also analysed by Northern hybridization with specific probes for heat shock proteins. The results clearly show that wheat plants respond to thermal stress by triggering the typical mechanisms of the heat shock response including activation of the heat shock genes, in developing grains as well as other plant parts.     

What the hyena's laugh tells: Sex, age, dominance and individual signature in the giggling call of Crocuta crocuta

Background  

Among mammals living in social groups, individuals form communication networks where they signal their identity and social status, facilitating social interaction. In spite of its importance for understanding of mammalian societies, the coding of individual-related information in the vocal signals of non-primate mammals has been relatively neglected. The present study focuses on the spotted hyena Crocuta crocuta, a social carnivore known for its complex female-dominated society. We investigate if and how the well-known hyena's laugh, also known as the giggle call, encodes information about the emitter.     

Influence of Environmental Factors on the Paralytic Shellfish Toxin Content and Profile of Alexandrium catenella (Dinophyceae) Isolated from the Mediterranean Sea

Laboratory experiments were designed to study the toxin content and profile of the Alexandrium catenella strain ACT03 (isolated from Thau Lagoon, French Mediterranean) in response to abiotic environmental factors under nutrient-replete conditions. This dinoflagellate can produce various paralytic shellfish toxins with concentrations ranging from 2.9 to 50.3 fmol/cell. The toxin profile was characterized by carbamate toxins (GTX3, GTX4 and GTX5) and N-sulfocarbamoyl toxins (C1, C2, C3 and C4). C2 dominated at 12–18 °C, but only for salinities ranging from 10 to 25 psu, whereas GTX5 became dominant at temperatures ranging from 21 to 30 °C at almost all salinities. There was no significant variation in the cellular toxin amount from 18 °C to 27 °C for salinities ranging between 30 and 40 psu. At salinities of 10 to 25 psu, the toxin concentrations always remained below 20 fmol/cell. Toxin content was stable for irradiance ranging from 10 to 70 μmol photons/m²/s then slightly increased. Overall, the toxin profile was more stable than the toxin content (fmol/cell), except for temperature and/or salinity values different from those recorded during Alexandrium blooms in Thau Lagoon.     

Tolerance of Amaranthus palmeri populations from California to postemergence herbicides at various growth stages

In recent years, poor control of Amarathus palmeri S. Wats. plants with glyphosate in many agricultural and non-crop has been observed in the San Joaquin Valley (SJV), California, USA. Studies were conducted to assess if these were glyphosate-resistant (GR) populations. Populations from 23 different locations of the SJV were exposed to glyphosate application of 840 g ae ha⁻¹ at the 5 to 8 leaf stage of the plant and compared against a known GR and glyphosate-susceptible (GS) population from New Mexico, USA. None of the plants from the SJV survived the glyphosate application suggesting that they were GS. Plant mortality following application of glyphosate (840 g ae ha⁻¹), glufosinate (490 g ai ha⁻¹), paraquat dichloride (660 g ai ha⁻¹), saflufenacil (50 g ai ha⁻¹), rimsulfuron (70 g ai ha⁻¹⁾, and a tank-mix of glyphosate (840 g ae ha⁻¹) + saflufenacil (50 g ai ha⁻¹) applied at the 4 to 6, 8 to 10, and 12 to 16 leaf stages of A. palmeri was determined on potted plants grown outdoors. Complete control was obtained with all the treatments applied at the 4 to 6 leaf stage but control was reduced to less than 70% and 20% with glyphosate and glufosinate, respectively at the later stages. The other treatments provided 100% control at all growth stages. Combinations of saflufenacil + glyphosate, saflufenacil + glufosinate, saflufenacil + dicamba, rimsulfuron + glyphosate, tembotrione + glyphosate, flumioxazin + pyroxasulfone + glyphosate, flumioxazin + pyroxasulfone + glyphosate, dicamba + paraquat dichloride, and glyphosate + glufosinate were also tested on 8 to 10 leaf stage A. palmeri plants and all the combinations provided 100% control.     

Determination of the genetic structure of remnant Morus boninensis Koidz. trees to establish a conservation program on the Bonin Islands, Japan

Background  

Morus boninensis, is an endemic plant of the Bonin (Ogasawara) Islands of Japan and is categorized as "critically endangered" in the Japanese red data book. However, little information is available about its ecological, evolutionary and genetic status, despite the urgent need for guidelines for the conservation of the species. Therefore, we adopted Moritz's MU concept, based on the species' current genetic structure, to define management units and to select mother tree candidates for seed orchards.     

Development of daily rhythmicity in heart rate and locomotor activity in the human fetus

Background  

Very little is known about the perinatal genesis of circadian rhythmicity in the human fetus. Some researchers have found evidence of rhythmicity early on in fetal development, whereas others have observed a slow development of rhythmicity during several years after birth.     

The impact of phages on interspecific competition in experimental populations of bacteria

Background  

Phages are thought to play a crucial role in the maintenance of diversity in natural bacterial communities. Theory suggests that phages impose density dependent regulation on bacterial populations, preventing competitive dominants from excluding less competitive species. To test this, we constructed experimental communities containing two bacterial species (Pseudomonas fluorescens and Pseudomonas aeruginosa) and their phage parasites. Communities were propagated at two environmental temperatures that reversed the outcome of competition in the absence of phage.     

Cost of resistance to trematodes in freshwater snail populations with low clonal diversity

Background

The persistence of high genetic variability in natural populations garners considerable interest among ecologists and evolutionary biologists. One proposed hypothesis for the maintenance of high levels of genetic diversity relies on frequency-dependent selection imposed by parasites on host populations (Red Queen hypothesis). A complementary hypothesis suggests that a trade-off between fitness costs associated with tolerance to stress factors and fitness costs associated with resistance to parasites is responsible for the maintenance of host genetic diversity.

Results

The present study investigated whether host resistance to parasites is traded off with tolerance to environmental stress factors (high/low temperatures, high salinity), by comparing populations of the freshwater snail Melanoides tuberculata with low vs. high clonal diversity. Since polyclonal populations were found to be more parasitized than populations with low clonal diversity, we expected them to be tolerant to environmental stress factors. We found that clonal diversity explained most of the variation in snail survival under high temperature, thereby suggesting that tolerance to high temperatures of clonally diverse populations is higher than that of populations with low clonal diversity.

Conclusions

Our results suggest that resistance to parasites may come at a cost of reduced tolerance to certain environmental stress factors.

     

Alleviation of salinity stress on germination of Leymus chinensis seeds by plant growth regulators and nitrogenous compounds under contrasting light/dark conditions

The effects of plant growth regulators (PGRs) and nitrogenous compounds on alleviating salinity stress on seed germination of Leymus chinensis in light (12 h light/12 h dark) and dark (24 h dark) conditions were determined in a laboratory experiment. Seed germination was compared at various combinations of salinity and germination‐promoting compounds. Seed germination percentages were 57 and 74% under non‐saline conditions in light and dark, respectively, suggesting that germination was light‐inhibited. Germination decreased significantly with increasing salinity level in both light and dark conditions, and the reduction was greater in light than in dark at each salinity level. Seed germination percentage decreased to 22 and 7% in light but only to 51 and 27% in dark, in 100 and 200 mm NaCl solutions respectively. The influence of PGRs and nitrogenous compounds in alleviating salinity stress varied with light and salinity condition; e.g., gibberellins (GA_4 + 7) significantly increased germination percentages from 22%, 7% and 0·3% to 47%, 23% and 15% in light at 100, 200 and 300 mm NaCl, respectively, while they showed no effect on germination in darkness. In contrast, sodium nitroprusside and cytokinin significantly increased germination percentage in darkness at all salinity levels, but showed no effect on germination in light at 200 and 300 mm NaCl. Fluridone was very effective in alleviating salinity stress on germination in both light and dark; however, it was lethal to seedlings. Thiourea had no effect in alleviating salinity stress in either light or dark. Thus, alleviation of salinity stress on seed germination of L. chinensis by germination‐promoting compounds is strongly dependent on chemicals and light conditions.     

Coexistence of diploid and triploid hybrid water frogs: population differences persist in the apparent absence of differential survival

Background  

The role of differential selection in determining the geographic distribution of genotypes in hybrid systems has long been discussed, but not settled. The present study aims to asses the importance of selection in structuring all-hybrid Pelophylax esculentus populations. These populations, in which the parental species (P. lessonae with genotype LL and P. ridibundus with genotype RR) are absent, have pond-specific proportions of diploid (LR) and triploid (LLR and LRR) genotypes.     

Clouded leopards, the secretive top-carnivore of South-East Asian rainforests: their distribution, status and conservation needs in Sabah, Malaysia

Background  

The continued depletion of tropical rainforests and fragmentation of natural habitats has led to significant ecological changes which place most top carnivores under heavy pressure. Various methods have been used to determine the status of top carnivore populations in rainforest habitats, most of which are costly in terms of equipment and time. In this study we utilized, for the first time, a rigorous track classification method to estimate population size and density of clouded leopards (Neofelis nebulosa) in Tabin Wildlife Reserve in north-eastern Borneo (Sabah).     

Emergence of physiological rhythmicity in term and preterm neonates in a neonatal intensive care unit

Background  

Biological rhythmicity, particularly circadian rhythmicity, is considered to be a key mechanism in the maintenance of physiological function. Very little is known, however, about biological rhythmicity pattern in preterm and term neonates in neonatal intensive care units (NICU). In this study, we investigated whether term and preterm neonates admitted to NICU exhibit biological rhythmicity during the neonatal period.     

Time for sex: nycthemeral distribution of human sexual behavior

Background  

Nycthemeral (daily) oscillation has been documented in a variety of physiological and behavioral processes. The present study was carried out to evaluate the existence of a nycthemeral rhythm of human sexual behavior and to identify environmental factors responsible for the rhythmic pattern.     

Effects of temperature and light on salinity tolerance during germination in two desert glycophytic grasses,Lasiurus scindicus and Panicum turgidum

The grasses Lasiurus scindicus and Panicum turgidum are among the most important forage species of the Arabian deserts. Both are ‘glycophytic’ or salt‐intolerant species, where seed germination becomes reduced by salinity effects. Here, we report experimental effects of light/darkness, temperature and NaCl salinity on seed germination and ‘recovery’ germination in these two species, after seeds had been transferred from saline solution to distilled water. Seeds were germinated in a range of salinities and incubated at a range of temperatures, in both light and darkness. Seeds of P. turgidum germinated significantly more in darkness than in light at temperatures 15–25°C, but the reverse was true at higher temperatures. Seeds of L. scindicus germinated well across a wide range of temperatures and in both light and darkness. In both species, germination decreased with the increase in salt concentration, and in P. turgidum germination was almost completely inhibited at a concentration of 200 mm . In saline solution, germination in darkness was significantly greater than in light at all the temperatures. Seeds of both species ‘recovered’ their germination capacity after transfer from saline solutions to distilled water. Germination recovery depended on both light and temperature of incubation in both species.     

Effect of Green Tea and Vitamin E Combination in Isoproterenol Induced Myocardial Infarction in Rats

The present study was aimed to investigate the combined effects of green tea and vitamin E on heart weight, body weight, serum marker enzymes, lipid peroxidation, endogenous antioxidants and membrane bound ATPases in isoproterenol (ISO)-induced myocardial infarction in rats. Adult male albino rats, treated with ISO (200 mg/kg, s.c.) for 2 days at an interval of 24 h caused a significant (P < 0.05) elevation of heart weight, serum marker enzymes, lipid peroxidation and Ca⁺² ATPase level whereas there was a significant (P < 0.05) decrease in body weight, endogenous antioxidants, Na⁺/ K⁺ ATPase and Mg⁺² ATPase levels. Administration of green tea (100 mg/kg/day, p.o.) and vitamin E (100 mg/kg/day, p.o.) together for 30 consecutive days and challenged with ISO on the day 29th and 30th, showed a significant (P < 0.05) decrease in heart weight, serum marker enzymes, lipid peroxidation, Ca⁺² ATPase and a significant increase in the body weight, endogenous antioxidants, Na⁺/K⁺ ATPase and Mg⁺² ATPase when compared with ISO treated group and green tea or vitamin E alone treated groups. These findings indicate the synergistic protective effect of green tea and vitamin E during ISO induced myocardial infarction in rats.     

Effects of intraspecific competition on the life cycle of the stonefly, <Emphasis Type="Italic">Nemurella pictetii</Emphasis> (Plecoptera: Nemouridae)

Background  

Considerable variation of life cycle duration in given insect species has been frequently recorded. Splitting of populations into cohorts with different life cycle lengths may occur, sometimes even between siblings from the same batch. Larval populations of the stonefly Nemurella pictetii in central Europe regularly split into a very fast developing and a normal univoltine cohort, leading to partial multivoltinism. The causes for such variation remain unknown but presumably act on the larval stage in which most of the life cycle is spent. We therefore studied possible effects of intraspecific competition on growth and development of larvae in the laboratory.     

Insecticide resistance, mixture potentiation and fitness in populations of the maize weevil (Sitophilus zeamais)

High levels of pyrethroid resistance and emerging organophosphate resistance in Brazilian populations of the maize weevil Sitophilus zeamais (Coleoptera: Curculionidae) led to the registration of esfenvalerate + fenitrothion against them. Thus, a survey of physiological and behavioural resistance was carried out in 27 insect populations for two pyrethroids, esfenvalerate and permethrin, and the esfenvalerate + fenitrothion mixture. Physiological resistance to fenitrothion was also assessed, as was the potentiation of the mixture. The potential fitness cost associated with insecticide resistance was also investigated. The resistance levels were low to fenitrothion (<14.1-fold), low to moderate to the pyrethroids (1.6–70.0-fold) and low to the pyrethroid-organophosphate mixture (<5-fold) with a high heterogeneity of response among populations. The potentiation of insecticidal activity achieved with the insecticide mixture was very high (>350-fold) reinforcing its usefulness for managing weevils. There was little variation in walking behaviour (and insecticide avoidance) among populations; there was no significant variation in fitness, body mass and respiration rate among the populations of the insect. These however, displayed variable rates of grain consumption and activity of amylase and lipase. A decrease in insecticide resistance in maize weevil populations was observed relative to previous studies, but with an initial development of resistance to the insecticide mixture. Behavioural and physiological resistance were not correlated and not associated with fitness cost. Our results support the use of esfenvalerate + fenitrothion against the maize weevil, which is likely to have reduced the levels of pyrethroid resistance in field populations. However, resistance to this mixture seems to be evolving, justifying concerns regarding its use.