Interaction between temperature and male pheromone in sexual isolation in Drosophila melanogaster

In Drosophila, female hydrocarbons are known to be involved in premating isolation between different species and pheromonal races. The role of male‐specific hydrocarbon polymorphism is not as well documented. The dominant cuticular hydrocarbon (CHC) in male D. melanogaster is usually 7‐tricosene (7‐T), with the exception of African populations, in which 7‐pentacosene (7‐P) is dominant. Here, we took advantage of a population from the Comoro Islands (Com), in which males fell on a continuum of low to high levels of 7‐T, to perform temperature selection and selection on CHCs' profiles. We conducted several experiments on the selected Com males to study the plasticity of their CHCs in response to temperature shift, their role in resistance to desiccation and in sexual selection. We then compared the results obtained for selected lines to those from three common laboratory strains with different and homogenous hydrocarbon profiles: CS, Cot and Tai. Temperature selection modified the CHC profiles of the Com males in few generations of selection. We showed that the 7‐P/7‐T ratio depends on temperature with generally more 7‐P at higher temperatures and observed a relationship between chain length and resistance to desiccation in both temperature‐ and phenotypically selected Com lines. There was partial sexual isolation between the flies with clear‐cut phenotypes within the phenotypically selected lines and the laboratory strains. These results indicate that the dominant male pheromones are under environmental selection and may have played a role in reproductive isolation.     

Hsp 12 is a LEA-like protein in Saccharomyces cerevisiae

LEA group I, II and III antibodies all recognised soluble proteins present in an extract of yeast (Saccharomyces cerevisiae). The smaller protein of the two recognised by the group I antibody displayed identical migration on SDS-PAGE to the pea seed LEA group I protein against which the antibody was raised. However, the antibody failed to recognise the predominant protein present after heating the extract at 80 °C for 10 min. This predominant protein, which also displayed identical migration on SDS-PAGE, was purified from the supernatant of the extract heated at 80 °C for 10 min. Peptide sequencing after CNBr cleavage identified the isolated protein as the heat shock protein HSP 12. Despite a previous report that HSP 12 is a heat shock protein, HSP 12 was found to increase in yeast grown at 37 °C compared with growth at 30 °C . However, increased amounts of HSP 12 were present in yeast after entry into stationary phase; this was enhanced by growth in the osmolytes NaCl and mannitol.     

The influence of the Miocene Mediterranean desiccation on the geographical expansion and genetic variation of Androcymbium gramineum (Cav.) McBride (Colchicaceae)

Chloroplast DNA (cpDNA) restriction site and isozyme data were combined to explore the spatial-temporal influence of the Messinian desiccation in the Mediterranean on the disjunct distribution of Androcymbium gramineum in Almería and Morocco (north and south of the straits of Gibraltar, respectively). Lack of evidence for different selective pressures, divergence time estimates based on the calibration of the isozyme molecular clock with the cpDNA data, the basal position of Almerian populations in the A. gramineum clade, and the much higher isozyme polymorphism in Almería suggest that (i) only a southern European range of A. gramineum existed before the Messinian [ approximately 11.2 million years ago (Ma), in the middle Miocene] and (ii) the desiccation of the Mediterranean basin about 5.5-4.5 Ma induced the migration of A. gramineum from Almería to Morocco (between 4.9 and 4.6 Ma, according to our time estimates). After the split into two allopatric units following the refilling of the Mediterranean, the major influence of drift associated with Plio-Pleistocene recurrent glaciation cycles and range expansions/contractions probably fostered the substantial interpopulation genetic differentiation observed within Almería (CGST = 0.41, average DNei = 0.185) and, to a lesser extent, within Morocco (CGST = 0.24, average DNei = 0.089), but did not hinder the maintenance of considerable levels of genetic variation in either geographical area (A = 2.14, HE = 0.230 and A = 1.90, HE = 0.213, respectively).     

PROTEINS IMMUNOLOGICALLY RELATED TO DEHYDRINS IN FUCOID ALGAE

Adult fucoid algae on Atlantic shores have well-characterized, species-specific tolerances to the varying levels of desiccation that occur from the low to high intertidal zones; however, less is known about embryonic tolerances and their mechanistic basis. We investigated this by 1) exposing embryos of Fucus evanescens C. Agardh, F. spiralis L., and F. vesiculosus L. from the Maine shore to osmotic desiccation in hypersaline seawater and 2) examining whether these embryos contain species-specific dehydrins, proteins first identified in higher plants that are hypothesized to confer tolerance to dehydration. Embryonic survival when cultured in hypersaline seawater >100 practical salinity units (psu) correlated with the position of these species in the intertidal zone (F. spiralis > F. vesiculosus > F. evanescens), but all 1-day-old embryos of these species tolerated treatment with 100 psu or lower seawater. Proteins (17–105 kDa) immunologically related to dehydrins were detected on western blots with dehydrin antibodies raised against a synthetic peptide representing the conserved motif of dehydrins in higher plants. These proteins were constitutive and unstable when subjected to prolonged (>15 min) temperatures above 55° C, unlike most higher plant dehydrins, which are inducible and remain soluble at 75°–100° C. The presence of these proteins was species- and stage-specific. Sperm of F. vesiculosus had a characteristic protein of 76 kDa, whereas eggs and embryos (6 h to 3 days old) had a 92-kDa protein. By 1 week of age, expression of the 92-kDa protein decreased, and the 35-kDa protein of adults was present. Embryos of A. nodosum L. and Pelvetia compressa J. Agardh DeToni contained an 85-kDa protein rather than the 92-kDa protein of Fucus embryos (F. distichus L., F. evanescens, F. spiralis, and F. vesiculosus). The 92-kDa protein became more abundant in embryos exposed to hyperosmotic seawater at 50 psu (F. evanescens and F. vesiculosus) or 150 psu (F. spiralis); however, dehydrin-like proteins of some molecular masses decreased in abundance simultaneously. Further characterization of these proteins is required to establish whether they protect embryos against intertidal desiccation.     

土体干缩裂缝研究进展

土体干缩裂缝的形成和发展是一个复杂的物理过程,会对土体的强度、稳定性和渗透性等产生影响,其影响范围广泛分布于土壤学、农业、工程地质和环境保护等学科.本文在明确土体干缩裂缝研究重要性的基础上,通过收集整理国内外有关土体干缩裂缝研究的既有文献资料,综述了土体干缩裂缝的理论研究、实用性研究以及裂缝形态定量分析研究,分析和讨论了土体干缩裂缝在研究领域、研究内容和研究方法方面的不足之处,并指出土体干缩裂缝的未来发展方向.     

A Putative LEA Protein,but no Trehalose,is Present in Anhydrobiotic Bdelloid Rotifers

Some eukaryotes, including bdelloid rotifer species, are able to withstand desiccation by entering a state of suspended animation. In this ametabolic condition, known as anhydrobiosis, they can remain viable for extended periods, perhaps decades, but resume normal activities on rehydration. Anhydrobiosis is thought to require accumulation of the non-reducing disaccharides trehalose (in animals and fungi) or sucrose (in plant seeds and resurrection plants), which may protect proteins and membranes by acting as water replacement molecules and vitrifying agents. However, in clone cultures of bdelloid rotifers Philodina roseola and Adineta vaga, we were unable to detect trehalose or other disaccharides in either control or dehydrating animals, as determined by gas chromatography. Indeed, trehalose synthase genes (tps) were not detected in these rotifer genomes, suggesting that bdelloids might not have the capacity to produce trehalose under any circumstances. This is in sharp contrast to other anhydrobiotic animals such as nematodes and brine shrimp cysts, where trehalose is present during desiccation. Instead, we suggest that adaptations involving proteins might be more important than those involving small biochemicals in rotifer anhydrobiosis: on dehydration, P. roseola upregulates a hydrophilic protein related to the late embryogenesis abundant (LEA) proteins associated with desiccation tolerance in plants. Since LEA-like proteins have also been implicated in the desiccation tolerance of nematodes and micro-organisms, it seems that hydrophilic protein biosynthesis represents a common element of anhydrobiosis across several biological kingdoms.     

Recipes for successful anhydrobiosis in bdelloid rotifers

We tested the effect of several environmental variables on the ability of three bdelloid rotifers (Macrotrachela quadricornifera, Philodina roseola and Adineta oculata) to recover from the anhydrobiotic state. The variables we examined were (1) rate of water evaporation, (2) relative humidity during anhydrobiosis, (3) temperature during anhydrobiosis, (4) duration of anhydrobiosis, and (5) rehydration rate. Our results indicate that bdelloids can regulate to some degree net water balance during onset and termination of anhydrobiosis.     

Responses of the resurrection plant <Emphasis Type="Italic">Haberlea rhodopensis</Emphasis> to high irradiance

The effect of high irradiance (HI) during desiccation and subsequent rehydration of the homoiochlorophyllous desiccation-tolerant shade plant Haberlea rhodopensis was investigated. Plants were irradiated with a high quantum fluence rate (HI; 350 μmol m⁻² s⁻¹ compared to ca. 30 μmol m⁻² s⁻¹ at the natural rock habitat below trees) and subjected either to fast desiccation (tufts dehydrated with naturally occurring thin soil layers) or slow desiccation (tufts planted in pots in peat-soil dehydrated by withholding irrigation). Leaf water content was 5 % of the control after 4 d of fast and 19 d of slow desiccation. Haberlea was very sensitive to HI under all conditions. After 19 d at HI, even in well-watered plants there was a strong reduction of rates of net photosynthesis and transpiration, contents of chlorophyll (Chl) and carotenoids, as well as photosystem 2 activity (detected by the Chl fluorescence ratio R_Fd). Simultaneously, the blue/red and green/red fluorescence ratios increased considerably suggesting increased synthesis of polyphenolic compounds. Desiccation of plants in HI induced irreversible changes in the photosynthetic apparatus and leaves did not recover after rehydration regardless of fast or slow desiccation. Only young leaves survived desiccation.     

Linking Physiology To Ecological Function: Environmental Conditions Affect Performance And Size Of The Intertidal Kelp Hedophyllum Sessile (Laminariales,Phaeophyceae)

For autogenic ecosystem engineers, body size is an aspect of individual performance that has direct connections to community structure; yet the complex morphology of these species can make it difficult to draw clear connections between the environment and performance. We combined laboratory experiments and field surveys to test the hypothesis that individual body size was determined by disparate localized physiological responses to environmental conditions across the complex thallus of the intertidal kelp Hedophyllum sessile, a canopy‐forming physical ecosystem engineer. We documented substantial (> 40%) declines in whole‐thallus photosynthetic potential (as Maximum Quantum Yield, MQY) as a consequence of emersion, which were related to greater than 10‐fold increases in intra‐thallus MQY variability (as Coefficient of Variation). In laboratory experiments, desiccation and high light levels during emersion led to lasting impairment of photosynthetic potential and an immediate > 25% reduction in area due to tissue contraction, which was followed by complete loss of structural integrity after three days of submersion. Tissue exposed to desiccation and high light during emersion had higher nitrogen concentrations and lower phlorotannin concentrations than tissue in control treatments (on average 1.36 and 0.1x controls, respectively), suggesting that conditions during emersion have the potential to affect food quality for consumers. Our data indicate that the complex thallus morphology of H. sessile may be critical to this kelp’s ability to persist in the intertidal zone despite the physiological challenges of emersion and encourage a more nuanced view of the concept of “sub‐lethal stress” on the scale of the whole individual.