Localization of sequences regulating ancestral and acquired sites of esterase6 activity in Drosophila melanogaster

We have broadly defined the DNA regions regulating esterase6 activity in several life stages and tissue types of D. melanogaster using P- element-mediated transformation of constructs that contain the esterase6 coding region and deletions or substitutions in 5' or 3' flanking DNA. Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and the primary sequences regulating its activity lie between -171 and -25 bp relative to the translation initiation site: deletion of these sequences decrease activity approximately 20-fold. Hemolymph activity is also modulated by four other DNA regions, three of which lie 5' and one of which lies 3' of the coding region. Of these, two have positive and two have negative effects, each of approximately twofold. Esterase6 activity is present also in two male reproductive tract tissues; the ejaculatory bulb, which is another ancestral activity site, and the ejaculatory duct, which is a recently acquired site within the melanogaster species subgroup. Activities in these tissues are at least in part independently regulated: activity in the ejaculatory bulb is conferred by sequences between -273 and -172 bp (threefold decrease when deleted), while activity in the ejaculatory duct is conferred by more distal sequences between -844 and -614 bp (fourfold decrease when deleted). The reproductive tract activity is further modulated by two additional DNA regions, one in 5' DNA (-613 to -284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to +2731 bp; threefold decrease when deleted) that probably overlaps the adjacent esteraseP gene. Collating these data with previous studies suggests that expression of EST6 in the ancestral sites is mainly regulated by conserved proximal sequences while more variable distal sequences regulate expression in the acquired ejaculatory duct site.      

Nucleotide variation at the hypervariable esterase 6 isozyme locus of Drosophila simulans

Esterase 6 (Est-6/EST6) is polymorphic in both Drosophila melanogaster and D. simulans for two common allozyme forms, as well as for several other less common variants. Parallel latitudinal clines in the frequencies of the common EST6-F and EST6-S allozymes in these species have previously been interpreted in terms of a shared amino acid polymorphism that distinguishes the two variants and is subject to selection. Here we compare the sequences of four D. simulans Est-6 isolates and show that overall estimates of nucleotide heterozygosity in both coding and 5' flanking regions are more than threefold higher than those obtained previously for this gene in D. melanogaster. Nevertheless, the ratio of replacement to exon silent-site polymorphism in D. simulans is less than the ratio of replacement to silent divergence between D. simulans and D. melanogaster, which could be the result of increased efficiency of selection against replacement polymorphisms in D. simulans or to divergent selection between the two species. We also find that the amino acid polymorphisms separating EST6- F and EST6-S in D. simulans are not the same as those that separate these allozymes in D. melanogaster, implying that the shared clines do not reflect shared molecular targets for selection. All comparisons within and between the two species reveal a remarkable paucity of variation in a stretch of nearly 400 bp immediately 5' of the gene, indicative of strong selective constraint to retain essential aspects of Est-6 promoter function.      

Rapid microstructural plasticity in the cortical semantic network following a short language learning session

Despite the clear importance of language in our life, our vital ability to quickly and effectively learn new words and meanings is neurobiologically poorly understood. Conventional knowledge maintains that language learning—especially in adulthood—is slow and laborious. Furthermore, its structural basis remains unclear. Even though behavioural manifestations of learning are evident near instantly, previous neuroimaging work across a range of semantic categories has largely studied neural changes associated with months or years of practice. Here, we address rapid neuroanatomical plasticity accompanying new lexicon acquisition, specifically focussing on the learning of action-related language, which has been linked to the brain’s motor systems. Our results show that it is possible to measure and to externally modulate (using transcranial magnetic stimulation (TMS) of motor cortex) cortical microanatomic reorganisation after mere minutes of new word learning. Learning-induced microstructural changes, as measured by diffusion kurtosis imaging (DKI) and machine learning-based analysis, were evident in prefrontal, temporal, and parietal neocortical sites, likely reflecting integrative lexico-semantic processing and formation of new memory circuits immediately during the learning tasks. These results suggest a structural basis for the rapid neocortical word encoding mechanism and reveal the causally interactive relationship of modal and associative brain regions in supporting learning and word acquisition.

This combined neuroimaging and brain stimulation study reveals rapid and distributed microstructural plasticity after a single immersive language learning session, demonstrating the causal relevance of the motor cortex in encoding the meaning of novel action words.     

Differences in relative air humidity affect responses to soil salinity in freshwater and salt marsh populations of the dominant grass species Phragmites australis

Hydrobiologia - Soil salinity diminishes the dominance of species and affects their distribution. Phragmites australis is a dominant ecosystem engineer with broad distribution, high intraspecific...     

Intraspecific differences of Asian/Australian Phragmites australis subgroups reveal no potentially invasive traits

Hydrobiologia - Phragmites australis is a cosmopolitan plant species with high intraspecific diversity and phenotypic plasticity. Due to its variability and large ecological niche breadth,...     

Isolation and Identification of the Microbiota of Danish Farmhouse and Industrially Produced Surface-Ripened Cheeses

For studying the microbiota of four Danish surface-ripened cheeses produced at three farmhouses and one industrial dairy, both a culture-dependent and culture-independent approach were used. After dereplication of the initial set of 433 isolates by (GTG)5-PCR fingerprinting, 217 bacterial and 25 yeast isolates were identified by sequencing of the 16S rRNA gene or the D1/D2 domain of the 26S rRNA gene, respectively. At the end of ripening, the cheese core microbiota of the farmhouse cheeses consisted of the mesophilic lactic acid bacteria (LAB) starter cultures Lactococcus lactis subsp. lactis and Leuconostoc mesenteorides as well as non-starter LAB including different Lactobacillus spp. The cheese from the industrial dairy was almost exclusively dominated by Lb. paracasei. The surface bacterial microbiota of all four cheeses were dominated by Corynebacterium spp. and/or Brachybacterium spp. Brevibacterium spp. was found to be subdominant compared to other bacteria on the farmhouse cheeses, and no Brevibacterium spp. was found on the cheese from the industrial dairy, even though B. linens was used as surface-ripening culture. Moreover, Gram-negative bacteria identified as Alcalignes faecalis and Proteus vulgaris were found on one of the farmhouse cheeses. The surface yeast microbiota consisted primarily of one dominating species for each cheese. For the farmhouse cheeses, the dominant yeast species were Yarrowia lipolytica, Geotrichum spp. and Debaryomyces hansenii, respectively, and for the cheese from the industrial dairy, D. hansenii was the dominant yeast species. Additionally, denaturing gradient gel electrophoresis (DGGE) analysis revealed that Streptococcus thermophilus was present in the farmhouse raw milk cheese analysed in this study. Furthermore, DGGE bands corresponding to Vagococcus carniphilus, Psychrobacter spp. and Lb. curvatus on the cheese surfaces indicated that these bacterial species may play a role in cheese ripening.     

Yeast diversity in rice-cassava fermentations produced by the indigenous Tapirapé people of Brazil

The Tapirapé people of the Tapi'it?wa tribe of Brazil produce several fermented foods and beverages, one of which is called 'cauim'. This beverage usually makes up the main staple food for adults and children. Several substrates are used in its production, including cassava, rice, corn, maize and peanuts. A fermentation using rice and cassava was conducted, and samples were collected at 4-h intervals for microbial analysis. The yeast population was low at the beginning of the fermentation and reached 6.9 x 10(7) CFU mL(-1) after 48 h. During the fermentation process common yeast species were identified by sequencing of the D1/D2 domain of the large-subunit (26S) rRNA gene. The predominant yeast species found was Candida tropicalis. Candida intermedia, Candida parapsilosis, Pichia guilliermondii, Saccharomyces cerevisiae and Trichosporon asahii were also found in high numbers during the fermentation. Exophiala dermatidis, often associated with blastomycosis, was found in the mass before inoculation and during the initial stages of the fermentation. Examination of these indigenous fermented foods may provide clues as to how food production and preservation can be expanded and thereby contribute to improve nutrition in native tribes in the region.     

An ERG channel inhibitor from the scorpion Buthus eupeus

The isolation of the peptide inhibitor of M-type K(+) current, BeKm-1, from the venom of the Central Asian scorpion Buthus eupeus has been described previously (Fillipov A. K., Kozlov, S. A., Pluzhnikov, K. A., Grishin, E. V., and Brown, D. A. (1996) FEBS Lett. 384, 277-280). Here we report the cloning, expression, and selectivity of BeKm-1. A full-length cDNA of 365 nucleotides encoding the precursor of BeKm-1 was isolated using the rapid amplification of cDNA ends polymerase chain reaction technique from mRNA obtained from scorpion telsons. Sequence analysis of the cDNA revealed that the precursor contains a signal peptide of 21 amino acid residues. The mature toxin consists of 36 amino acid residues. BeKm-1 belongs to the family of scorpion venom potassium channel blockers and represents a new subgroup of these toxins. The recombinant BeKm-1 was produced as a Protein A fusion product in the periplasm of Escherichia coli. After cleavage and high performance liquid chromatography purification, recombinant BeKm-1 displayed the same properties as the native toxin. Three BeKm-1 mutants (R27K, F32K, and R27K/F32K) were generated, purified, and characterized. Recombinant wild-type BeKm-1 and the three mutants partly inhibited the native M-like current in NG108-15 at 100 nm. The effect of the recombinant BeKm-1 on different K(+) channels was also studied. BeKm-1 inhibited hERG1 channels with an IC(50) of 3.3 nm, but had no effect at 100 nm on hEAG, hSK1, rSK2, hIK, hBK, KCNQ1/KCNE1, KCNQ2/KCNQ3, KCNQ4 channels, and minimal effect on rELK1. Thus, BeKm-1 was shown to be a novel specific blocker of hERG1 potassium channels.