Reciprocal Regulation of Epileptiform Neuronal Oscillations and Electrical Synapses in the Rat Hippocampus

Gap junction (GJ) channels have been recognized as an important mechanism for synchronizing neuronal networks. Herein, we investigated the participation of GJ channels in the pilocarpine-induced status epilepticus (SE) by analyzing electrophysiological activity following the blockade of connexins (Cx)-mediated communication. In addition, we examined the regulation of gene expression, protein levels, phosphorylation profile and distribution of neuronal Cx36, Cx45 and glial Cx43 in the rat hippocampus during the acute and latent periods. Electrophysiological recordings revealed that the GJ blockade anticipates the occurrence of low voltage oscillations and promotes a marked reduction of power in all analyzed frequencies.Cx36 gene expression and protein levels remained stable in acute and latent periods, whereas upregulation of Cx45 gene expression and protein redistribution were detected in the latent period. We also observed upregulation of Cx43 mRNA levels followed by changes in the phosphorylation profile and protein accumulation. Taken together, our results indisputably revealed that GJ communication participates in the epileptiform activity induced by pilocarpine. Moreover, considering that specific Cxs undergo alterations through acute and latent periods, this study indicates that the control of GJ communication may represent a focus in reliable anti-epileptogenic strategies.     

Finding Hybrid Incompatibilities Using Genome Sequences from Hybrid Populations

Natural hybrid zones offer a powerful framework for understanding the genetic basis of speciation in progress because ongoing hybridization continually creates unfavorable gene combinations. Evidence indicates that postzygotic reproductive isolation is often caused by epistatic interactions between mutations in different genes that evolved independently of one another (hybrid incompatibilities). We examined the potential to detect epistatic selection against incompatibilities from genome sequence data using the site frequency spectrum (SFS) of polymorphisms by conducting individual-based simulations in SLiM. We found that the genome-wide SFS in hybrid populations assumes a diagnostic shape, with the continual input of fixed differences between source populations via migration inducing a mass at intermediate allele frequency. Epistatic selection locally distorts the SFS as non-incompatibility alleles rise in frequency in a manner analogous to a selective sweep. Building on these results, we present a statistical method to identify genomic regions containing incompatibility loci that locates departures in the local SFS compared with the genome-wide SFS. Cross-validation studies demonstrate that our method detects recessive and codominant incompatibilities across a range of scenarios varying in the strength of epistatic selection, migration rate, and hybrid zone age. Our approach takes advantage of whole genome sequence data, does not require knowledge of demographic history, and can be applied to any pair of nascent species that forms a hybrid zone.     

An efficient Agrobacterium tumefaciens-mediated transformation method for Simplicillium subtropicum (Hypocreales: Cordycipitaceae)

Filamentous fungi are the organisms of choice for most industrial biotechnology. Some species can produce a variety of secondary metabolites and enzymes of commercial interest, and the production of valuable molecules has been enhanced through different molecular tools. Methods for genetic manipulation and transformation have been essential for the optimization of these organisms. The genus Simplicillium has attracted increased attention given several potential biotechnological applications. The Simplicillium genus harbors several entomopathogenic species and some isolates have been explored for bioremediation of heavy metal contaminants. Furthermore, the myriad of secondary metabolites isolated from Simplicillium spp. render these organisms as ideal targets for deep exploration and further biotechnological mining possibilities. However, the lack of molecular tools hampered the exploration of this genus. Thus, an Agrobacterium tumefaciens-mediated transformation method was established for Simplicillium subtropicum, employing the far-red fluorescent protein TURBOFP635/Katushka, as a visual marker, and the selection marker SUR gene, that confers resistance to chlorimuron ethyl. Notably, one round of transformation using the established method yielded almost 400 chlorimuron resistant isolates. Furthermore, these transformants displayed mitotic stability for, at least, five generations. We anticipate that this method can be useful for deep molecular exploration and improvement of strains in the Simplicillium genus.     

Dynamics of common reed (Phragmites australisTrin.) in Swiss fens with different management

Dynamics of common reed (Phragmites australisTrin.) in Central Europe have so far mostly beeninvestigated in connection with studies on reed`die-back' along lake shores. However, there hasrecently been increasing concern about reed expansionat terrestrial sites, such as fens and wet grasslands.In this paper we report on the results of fourseparate studies which monitored reed dynamics inSwiss fens with various mowing regimes over a periodof 4 to 15 years. The first study compared unmownplots with plots mown in winter in a triennialrotation; the second one included unmown plots, plotsmown in summer, and plots mown in winter; the thirdone compared plots mown in June and September withplots only mown in September; the fourth studyinvestigated only plots mown in September. Shootnumber and shoot size were recorded in permanentquadrats. In all studies the performance of P.australisfluctuated without trend or tended todecrease during the period investigated. Thedecreasing tendency concerned shoot size rather thanshoot number, and within a given study it was strongerfor plots with initially taller shoots. The variousmowing regimes did hardly influence these changes.Mowing in winter every three years reduced shoot sizein the year after mowing, but not on the long term.Mowing every year in late summer reduced the shootsize compared with unmown plots on the short term, butthis effect almost disappeared on the long term, aftermowing had become biennial. Mowing in June (inaddition to in September) caused no noticeableeffects. We conclude that other factors (e.g. weatherconditions, competition, or population processes) aremore important than management in determining theabundance of P. australisin the fen communitiesinvestigated here, although long-term effects ofmowing in summer still need more investigation. As apractical consequence it is suggested that at siteswhich are not strongly dominated by P.australis, as most of those investigated here,reducing the performance of this species should notconstitute a major target of nature conservationmanagement, nor can its dynamics be used as anindicator for management success before underlyingcauses are better understood.     

Population genetics of the American eel (Anguilla rostrata): FST = 0 and North Atlantic Oscillation effects on demographic fluctuations of a panmictic species

We performed population genetic analyses on the American eel (Anguilla rostrata) with three main objectives. First, we conducted the most comprehensive analysis of neutral genetic population structure to date to revisit the null hypothesis of panmixia in this species. Second, we used this data to provide the first estimates of contemporary effective population size (N_e) and to document temporal variation in effective number of breeders (N_b) in American eel. Third, we tested for statistical associations between temporal variation in the North Atlantic Oscillation (NAO), the effective number of breeders and two indices of recruit abundance. A total of 2142 eels from 32 sampling locations were genotyped with 18 microsatellite loci. All measures of differentiation were essentially zero, and no evidence for significant spatial or temporal genetic differentiation was found. The panmixia hypothesis should thus be accepted for this species. N_b estimates varied by a factor of 23 among 12 cohorts, from 473 to 10 999. The effective population size N_e was estimated at 10 532 (95% CI, 9312–11 752). This study also showed that genetically based demographic indices, namely N_b and allelic richness (Ar), can be used as surrogates for the abundance of breeders and recruits, which were both shown to be positively influenced by variation during high (positive) NAO phases. Thus, long‐term genetic monitoring of American glass eels at several sites along the North American Atlantic coast would represent a powerful and efficient complement to census monitoring to track demographic fluctuations and better understand their causes.     

Molecular mapping in tropical maize (Zea mays L.) using microsatellite markers. 2. Quantitative trait loci (QTL) for grain yield, plant height, ear height and grain moisture

A previous genetic map containing 117 microsatellite loci and 400 F(2) plants was used for quantitative trait loci (QTL) mapping in tropical maize. QTL were characterized in a population of 400 F(2:3) lines, derived from selfing the F(2) plants, and were evaluated with two replications in five environments. QTL determinations were made from the mean of these five environments. Grain yield (GY), plant height (PH), ear height (EH) and grain moisture (GM) were measured. Variance components for genotypes (G), environments (E) and GxE interaction were highly significant for all traits. Heritability was 0.69 for GY, 0.66 for PH, 0.67 for EH and 0.23 for GM. Using composite interval mapping (CIM), a total of 13 distinct QTLs were identified: four for GY, four for PH and five for EH. No QTL was detected for GM. The QTL explained 32.73 % of the phenotypic variance of GY, 24.76 % of PH and 20.91 % of EH. The 13 QTLs displayed mostly partial dominance or overdominance gene action and mapped to chromosomes 1, 2, 7, 8 and 9. Most QTL alleles conferring high values for the traits came from line L-14-4B. Mapping analysis identified genomic regions associated with two or more traits in a manner that was consistent with correlation among traits, supporting either pleiotropy or tight linkage among QTL. The low number of QTLs found, can be due to the great variation that exists among tropical environments.     

Nitrogen limitation and microbial diversity at the treeline

Tree growth limitation at treeline has mainly been studied in terms of carbon limitation while effects and mechanisms of potential nitrogen (N) limitation are barely known, especially in the southern hemisphere. We investigated how soil abiotic properties and microbial community structure and composition change from lower to upper sites within three vegetation belts (Nothofagus betuloides and N. pumilio forests, and alpine vegetation) across an elevation gradient (from 0 to 650 m a.s.l.) in Cordillera Darwin, southern Patagonia. Increasing elevation was associated with a decrease in soil N‐NH₄⁺ availability within the N. pumilio and the alpine vegetation belt. Within the alpine vegetation belt, a concurrent increase in the soil C:N ratio was associated with a shift from bacterial‐dominated in lower alpine sites to fungal‐dominated microbial communities in upper alpine sites. Lower forested belts (N. betuloides, N. pumilio) exhibited more complex patterns both in terms of soil properties and microbial communities. Overall, our results concur with recent findings from high‐latitude and altitude ecosystems showing decreased nutrient availability with elevation, leading to fungal‐dominated microbial communities. We suggest that growth limitation at treeline may result, in addition to proximal climatic parameters, from a competition between trees and soil microbial communities for limited soil inorganic N. At higher elevation, soil microbial communities could have comparably greater capacities to uptake soil N than trees, and the shift towards a fungal‐dominated community would favour N immobilization over N mineralization. Though evidences of altered nutrient dynamics in tree and alpine plant tissue with increasing altitude remain needed, we contend that the measured residual low amount of inorganic N available for trees in the soil could participate to the establishment limitation. Finally, our results suggest that responses of soil microbial communities to elevation could be influenced by functional properties of forest communities for instance through variations in litter quality.     

Jatropha curcas L. (Euphorbiaceae) exhibits a mixed mating system, high correlated mating and apomixis

The hierarchical mating system among and within fruits of Jatropha curcas was investigated in a base population using five microsatellite loci, employing mixed mating and correlated mating models. Open-pollinated fruits were collected from 15 randomly selected seed trees, sampling seven fruits per tree for a total of 21 seeds from each tree. We detected multilocus genotypes identical to the mother tree in 13 % of offspring, implying the occurrence of apomixis in J. curcas. The presumed apomictic individuals were excluded from the analysis of the remaining results. Evidence of substantial selfing was provided by the average multilocus outcrossing rate (t _m?=?0.683), showing that the species exhibits a mixed mating system. The outcrossing rate showed a large variation among seed trees, ranging from 0.21 to 1.0, indicating that the species is not self-incompatible. Significant differences were detected between the multilocus and the single locus outcrossing rates (t _m???t _s?=?0.347) that suggested mating among related individuals, possibly because of the presence of individuals from the same progeny (sibs) in the base population. The multilocus paternity correlation was extremely high for the population (r _p(m)?=?0.999), indicating that the progenies were manly composed of full-sibs. As a consequence of selfing and a high paternity correlation, the co-ancestry coefficient within the progeny was higher (Θ?=?0.369) than expected for panmictic populations. Our results indicated that J. curcas produces seeds asexually by apomixis and sexually by a mixed mating system, combining selfing and outcrossing.