Reproductive and competitive interactions among gametophytes of the allotetraploid fern Dryopteris corleyi and its two diploid parents

Background and Aims

Several models predict that the establishment of polyploids within diploid populations is enhanced by non-random mating (i.e. selfing and assortative mating) of cytotypes and by a higher relative fitness of polyploids. This report assesses the role that antheridiogens (i.e. maleness-inducing pheromones) and intercytotype differences in growth rate have on polyploid performance.

Methods

Three buckler-fern species were studied: the allotetraploid Dryopteris corleyi and its diploid parents, D. aemula and D. oreades. In one experiment, gametophytes of these species were cultured under rich growth conditions to compare the timing of gametangia production. The substrata on which these gametophytes had grown were used as antheridiogen sources in a second experiment. The three species were combined as source and target of antheridiogen (i.e. nine species pairs). Timing of antheridia production and gametophyte size were determined after those antheridiogen treatments.

Key Results

Under rich growth conditions the allotetraploid produced archegonia earlier than those of diploid parents. Female gametophytes of the three species produced antheridiogens that inhibited growth and favoured maleness both within and among species. Gametophyte size was similar in the three species but antheridia formed earlier in the allotetraploid.

Conclusions

Unisexuality, promoted by non-specific antheridiogens, enhances random mating both within and among species. The resulting hybridization can favour the reproductive exclusion of the allopolyploid in sites where it is outnumbered by diploids. However, the earlier production of gametangia in the allotetraploid favours assortative mating and may thus counterbalance reproductive exclusion.Key words: Allopolyploidy, antheridiogen, assortative mating, Dryopteris aemula, Dryopteris corleyi, Dryopteris oreades, gametophytes, gender expression, minority cytotype exclusion     

Intrinsic Protein Phosphorylation in Synaptosomal Plasma Membrane Fragments: A Comparison of Cerebral Cortex Tissue from Several Species, Including Human Biopsy Specimens

Intrinsic protein phosphorylation was studied in synaptosomal membrane fragments made from cerebral cortex tissue taken from the following species: human (biopsy specimens), ox, rat, rabbit, guinea pig and mouse. Membrane fragments from all species exhibited a qualitatively similar range of protein acceptors phosphorylated by cyclic AMP-dependent protein kinase activity; contrary to a previous report, no evidence for cyclic GMP-dependent protein kinase activity was found in the human material. With the exception of membrane fragments prepared from ox brain, all the preparations exhibited the same range of Ca2+-dependent protein kinase activity. Ox brain obtained from a slaughterhouse yielded membranes containing no Ca2+-dependent protein kinase activity, but this may have been due to unavoidable postmortem losses.     

Fossil pollen grains of Asteraceae from the Miocene of Patagonia: Nassauviinae affinity

Fossil pollen grains with morphological features unique in the subtribe Nassauviinae (tribe Mutisieae, Asteraceae) occur in Miocene marine deposits of eastern Patagonia, southern South America. A new morphogenus and two morphospecies are proposed to assemble fossil pollen grains characterized by having a complex bilayered exine structure with delicate columellae, separated by an internal tectum. Subprolate specimens with Trixis exine type (ectosexine thinner than endosexine, straight internal tectum) are referred to Huanilipollis cabrerae. This species is similar to pollen of recent Holocheilus, Jungia, and Proustia. Suboblate specimens with Oxyphyllum exine type (ectosexine and endosexine equally thick, zigzag internal tectum) are referred to Huanilipollis criscii. This species is similar to pollen of recent Triptilion. The spore/pollen sequences in which Nassauviinae pollen types occur suggest a wide range of vegetation types varying from forest dominated during the Early Miocene (Chenque Formation) to virtually xerophytic ones during the Late Miocene (Puerto Madryn Formation). The subtribe Nassauviinae comprises 25 genera and ca. 320 species of vines, shrubs and low trees endemic to America with a wide range of ecological preferences; the nearest living relatives of the fossil types being mostly confined to humid landscapes. The unusual occurrence of these groups during the arid characterized Late Miocene time could be attributed to the complex interplay of the mountain uplift and global circulation patterns. These forcing factors would have created a mosaic of different habitats with both patches of forest and dry-adapted species developing in relatively small regions. This is the first fossil record of Nassauviinae and confirms that this subtribe of Asteraceae was already differentiated in the Miocene.     

Wolf population genetics in Europe: a systematic review,meta‐analysis and suggestions for conservation and management

The grey wolf (Canis lupus) is an iconic large carnivore that has increasingly been recognized as an apex predator with intrinsic value and a keystone species. However, wolves have also long represented a primary source of human–carnivore conflict, which has led to long‐term persecution of wolves, resulting in a significant decrease in their numbers, genetic diversity and gene flow between populations. For more effective protection and management of wolf populations in Europe, robust scientific evidence is crucial. This review serves as an analytical summary of the main findings from wolf population genetic studies in Europe, covering major studies from the ‘pre‐genomic era’ and the first insights of the ‘genomics era’. We analyse, summarize and discuss findings derived from analyses of three compartments of the mammalian genome with different inheritance modes: maternal (mitochondrial DNA), paternal (Y chromosome) and biparental [autosomal microsatellites and single nucleotide polymorphisms (SNPs)]. To describe large‐scale trends and patterns of genetic variation in European wolf populations, we conducted a meta‐analysis based on the results of previous microsatellite studies and also included new data, covering all 19 European countries for which wolf genetic information is available: Norway, Sweden, Finland, Estonia, Latvia, Lithuania, Poland, Czech Republic, Slovakia, Germany, Belarus, Russia, Italy, Croatia, Bulgaria, Bosnia and Herzegovina, Greece, Spain and Portugal. We compared different indices of genetic diversity in wolf populations and found a significant spatial trend in heterozygosity across Europe from south‐west (lowest genetic diversity) to north‐east (highest). The range of spatial autocorrelation calculated on the basis of three characteristics of genetic diversity was 650?850 km, suggesting that the genetic diversity of a given wolf population can be influenced by populations up to 850 km away. As an important outcome of this synthesis, we discuss the most pressing issues threatening wolf populations in Europe, highlight important gaps in current knowledge, suggest solutions to overcome these limitations, and provide recommendations for science‐based wolf conservation and management at regional and Europe‐wide scales.     

Population genetics structure of glyphosate‐resistant Johnsongrass (Sorghum halepense L. Pers) does not support a single origin of the resistance

Single sequence repeats (SSR) developed for Sorghum bicolor were used to characterize the genetic distance of 46 different Sorghum halepense (Johnsongrass) accessions from Argentina some of which have evolved toward glyphosate resistance. Since Johnsongrass is an allotetraploid and only one subgenome is homologous to cultivated sorghum, some SSR loci amplified up to two alleles while others (presumably more conserved loci) amplified up to four alleles. Twelve SSR providing information of 24 loci representative of Johnsongrass genome were selected for genetic distance characterization. All of them were highly polymorphic, which was evidenced by the number of different alleles found in the samples studied, in some of them up to 20. UPGMA and Mantel analysis showed that Johnsongrass glyphosate‐resistant accessions that belong to different geographic regions do not share similar genetic backgrounds. In contrast, they show closer similarity to their neighboring susceptible counterparts. Discriminant Analysis of Principal Components using the clusters identified by K‐means support the lack of a clear pattern of association among samples and resistance status or province of origin. Consequently, these results do not support a single genetic origin of glyphosate resistance. Nucleotide sequencing of the 5‐enolpyruvylshikimate‐3‐phosphate synthase (EPSPS) encoding gene from glyphosate‐resistant and susceptible accessions collected from different geographic origins showed that none presented expected mutations in aminoacid positions 101 and 106 which are diagnostic of target‐site resistance mechanism.     

Dissecting the energy metabolism in Mycoplasma pneumoniae through genome‐scale metabolic modeling

Mycoplasma pneumoniae, a threatening pathogen with a minimal genome, is a model organism for bacterial systems biology for which substantial experimental information is available. With the goal of understanding the complex interactions underlying its metabolism, we analyzed and characterized the metabolic network of M. pneumoniae in great detail, integrating data from different omics analyses under a range of conditions into a constraint‐based model backbone. Iterating model predictions, hypothesis generation, experimental testing, and model refinement, we accurately curated the network and quantitatively explored the energy metabolism. In contrast to other bacteria, M. pneumoniae uses most of its energy for maintenance tasks instead of growth. We show that in highly linear networks the prediction of flux distributions for different growth times allows analysis of time‐dependent changes, albeit using a static model. By performing an in silico knock‐out study as well as analyzing flux distributions in single and double mutant phenotypes, we demonstrated that the model accurately represents the metabolism of M. pneumoniae. The experimentally validated model provides a solid basis for understanding its metabolic regulatory mechanisms.     

MinC Protein Shortens FtsZ Protofilaments by Preferentially Interacting with GDP-bound Subunits

The interaction of MinC with FtsZ and its effects on FtsZ polymerization were studied under close to physiological conditions by a combination of biophysical methods. The Min system is a widely conserved mechanism in bacteria that ensures the correct placement of the division machinery at midcell. MinC is the component of this system that effectively interacts with FtsZ and inhibits the formation of the Z-ring. Here we report that MinC produces a concentration-dependent reduction in the size of GTP-induced FtsZ protofilaments (FtsZ-GTP) as demonstrated by analytical ultracentrifugation, dynamic light scattering, fluorescence correlation spectroscopy, and electron microscopy. Our experiments show that, despite being shorter, FtsZ protofilaments maintain their narrow distribution in size in the presence of MinC. The protein had the same effect regardless of its addition prior to or after FtsZ polymerization. Fluorescence anisotropy measurements indicated that MinC bound to FtsZ-GDP with a moderate affinity (apparent K_D ∼10 μm at 100 mm KCl and pH 7.5) very close to the MinC concentration corresponding to the midpoint of the inhibition of FtsZ assembly. Only marginal binding of MinC to FtsZ-GTP protofilaments was observed by analytical ultracentrifugation and fluorescence correlation spectroscopy. Remarkably, MinC effects on FtsZ-GTP protofilaments and binding affinity to FtsZ-GDP were strongly dependent on ionic strength, being severely reduced at 500 mm KCl compared with 100 mm KCl. Our results support a mechanism in which MinC interacts with FtsZ-GDP, resulting in smaller protofilaments of defined size and having the same effect on both preassembled and growing FtsZ protofilaments.     

Aportaciones de los tests de supresión de cortisol al conocimiento de los trastornos psiquiátricos: revisión narrativa de la literatura

Activity of the hypothalamic-pituitary-adrenal axis had been studied for the past half century, when some researchers noted that some patients with Cushing's syndrome and severe mood disorders had high baseline cortisol levels, which resulted in an inhibited response in the 1 mg dexamethasone suppression test. Altered dexamethasone suppression test results were subsequently found in many psychiatric diseases, including anorexia nervosa, obsessive-compulsive disorder, degenerative dementia, bipolar disorders, and schizophrenia. The relationship between high baseline cortisol levels and stress has also been studied. Some researches on the genesis of borderline personality disorder focused on traumatic childhood backgrounds. Other investigations aimed at elucidating the relationship between traumatic backgrounds and some psychiatric disorders noted that patients with post-traumatic stress disorder and borderline personality disorder showed an enhanced cortisol suppression with low cortisol doses (0.5 mg). Recent studies showed that use of an ultra-low dose of cortisol during the dexamethasone suppression test may be helpful for deteting disorders with hyperactivity of the hypothalamic-pituitary-adrenal axis.Recent advances in neuroimaging support the existence of hyperactivity of the hypothalamic-pituitary-adrenal axis in patients with borderline personality disorder, relating a decreased pituitary gland volume to major traumatic backgrounds and suicidal attempts. The purpose of this paper is to make a narrative review of research using dexamethasone suppression test in psychiatric disorders, in order to ascertain its value as a supplemental diagnostic test or as a prognostic marker.