The dynamics of three shrub species in a fire-prone temperate savanna: the interplay between the seed bank, seed rain and fire regime

A model was developed to assess how the seed rain and fire regime affect seed bank dynamics and seedling establishment of three native shrub species (Acanthostyles buniifolius, Baccharis pingraea and Baccharis dracunculifolia) with different regeneration strategies, in temperate South American savanna. Seed bank and seed rain were quantified for each species under different fire regimes, and their relative roles in regeneration were evaluated. All species had short-term persistent seed banks and high annual variability in seed production. A high proportion of seeds deposited in the seed rain produced seedlings after fire; few entered the soil seed bank. Fire killed a high proportion of the seeds in the soil seed bank. Seedlings derived from the seed rain had a higher probability of surviving for 2 years than seedlings emerging from the soil seed bank. In the absence of fire, establishment depended on germination both from the seed rain and the soil seed bank, whereas with annual fire, establishment was primarily dependent on germination of seeds arriving in the annual seed rain, regardless of species’ regeneration strategies. These results help to explain changes in the vegetation of South American temperate savannas as a result of changes in fire regime and grazing management during the last 50 years. By revealing the crucial roles of the soil seed bank and seed rain in regeneration, this study provides vital information for the development of appropriate management practices to control populations of shrub species with different regeneration strategies in South American temperate savannas.     

Nuclear Localization of p38 MAPK in Response to DNA Damage

p38 MAP kinase (MAPK) is activated in response to environmental stress, cytokines and DNA damage, and mediates death, cell differentiation and cell cycle checkpoints. The intracellular localization of p38 MAPK upon activation remains unclear, and may depend on the stimulus. We show here that activation of p38 MAPK by stimuli that induce DNA double strand breaks (DSBs), but not other stimuli, leads to its nuclear translocation. In addition, naturally occurring DSBs generated through V(D)J recombination in immature thymocytes also promote nuclear accumulation of p38 MAPK. Nuclear translocation of p38 MAPK does not require its catalytic activity, but is induced by a conformational change of p38 MAPK triggered by phosphorylation within the active site. The selective nuclear accumulation of p38 MAPK in response to DNA damage could be a mechanism to facilitate the phosphorylation of p38 MAPK nuclear targets for the induction of a G2/M cell cycle checkpoint and DNA repair.     

The micro-biota of a sub-surface monument the medieval chapel of St. Virgil (Vienna, Austria)

The medieval chapel of St. Virgil is located sub-surface beneath the square of the dome of St. Stephen, in the heart of Vienna. The walls of the chapel are in direct contact with the surrounding soil. The water migrating horizontally into the walls of the chapel carries a huge load of soluble salts which crystallize on the surface of the walls and within the material. This phenomenon is causing material losses and destruction of original medieval fineries and paintings. Moreover, the salt creates special living conditions for microbes growing on and in the walls which is characterized by a high osmotic stress. The diversity of the micro-biota was studied both by cultivation and molecular techniques [a combination of denaturing gradient gel electrophoresis (DGGE) of PCR-amplified DNA encoding 16S rRNA and the construction of clone libraries]. The fungal diversity was found to be relatively low, albeit cell counts show more than 10⁵ colony forming units per gram of wall material. In the contrary, the diversity of bacteria was found to be high (more than 8 different genera). Furthermore, a community of extremely halophilic archaea was detected consisting of different species of two predominant genera, i.e., Halococcus and Halobacterium.     

Onychomycosis Due to <Emphasis Type="Italic">Aspergillus</Emphasis> spp.: a Current Review

Purpose of Review

The incidence of onychomycosis by Aspergillus has shown an increase in recent years, representing 34–60% of onychomycosis due to non-dermatophyte molds. At least 26 species of Aspergillus causing onychomycosis have been reported, some of which may be morphologically indistinguishable but genetically distinct, even in their susceptibility profile to antifungals. So in the diagnosis of this pathology, it is necessary to use both conventional and molecular methods to get to the identification of the fungus at the species level and thus establish the appropriate treatment.

Recent Findings

The current taxonomy of the genus Aspergillus includes sections that are made up of species whose morphology is almost identical but have different patterns of susceptibility to antifungals. Advances in the taxonomy of these fungi reveal the need to combine phenotypic methods (analysis of microscopic and macroscopic characteristics) with molecular ones (amplification and sequencing of fragments of the β-tubulin and calmodulin genes) to achieve their correct identification at the level of species.

Summary

From the demonstration of Aspergillus as the primary agent of onychomycosis, an increase in the incidence of this pathology worldwide has been reported, whose treatment is usually complicated. Various species of Aspergillus can cause nail infection but may respond differently to antifungal treatment, so it is important to know their epidemiology, clinical characteristics, etiologic agents, diagnostic methods, and treatment.

     

Initial characterization of the microenvironment that regulates connective tissue degradation in amniochorion during normal human labor.

Extracellular matrix degradation in fetal membranes leading to its rupture is coupled to myometrial activity and cervical ripening during human normal labor. Mechanisms which modulate collagen degradation in amniochorion during labor have not been elucidated. Initial characterization of the effect of different blood compartments on connective tissue degradation in amniochorion during human labor was explored. Amniochorion explants were stimulated with plasma of maternal venous blood, umbilical cord blood or placental blood, obtained from women with pregnancies at term, with or without labor. MMP-2 and MMP-9 activities were quantified in conditioned media by gelatin-zymography as an index of connective tissue degradation. Collagen content was measured in tissue explants and collagen fibrils distribution was examined by electron microscopy. Placental plasma from term pregnancies, with or without labor, is enriched with soluble signals that enhance the in vitro MMP-9 production by amniochorion. Accompanying ultrastructural distortion of collagen fibers and demonstration of collagen degradation fragments confirmed induction of extracellular matrix degradation. Control experiments in which MMP-9 activity was blocked with TIMP-1 resulted in inhibition of all the above mentioned changes. These results suggest that placental intervillous space is a functional compartment in which mediators capable to induce collagen degradation in amniochorion are selectively expressed during human labor.     

Extensive transcriptomic studies on the roles played by abscisic acid and auxins in the development and ripening of strawberry fruits

Strawberry is an ideal model for studying the molecular biology of the development and ripening of non-climacteric fruits. Hormonal regulation of gene expression along all these processes in strawberries is still to be fully elucidated. Although auxins and ABA have been pointed out as the major regulatory hormones, few high-throughput analyses have been carried out to date. The role for ethylene and gibberellins as regulatory hormones during the development and ripening of the strawberry fruit remain still elusive. By using a custom-made and high-quality oligo microarray platform done with over 32,000 probes including all of the genes actually described in the strawberry genome, we have analysed the expression of genes during the development and ripening in the receptacles of these fruits. We classify these genes into two major groups depending upon their temporal and developmental expression. First group are genes induced during the initial development stages. The second group encompasses genes induced during the final maturation and ripening processes. Each of these two groups has been also divided into four sub-groups according their pattern of hormonal regulation. By analyzing gene expression, we clearly show that auxins and ABA are the main and key hormones that combined or independently are responsible of the development and ripening process. Auxins are responsible for the receptacle fruit development and, at the same time¸ prevent ripening by repressing crucial genes. ABA regulates the expression of the vast majority of genes involved in the ripening. The main genes expressed under the control of these hormones are presented and their physiological rule discussed. We also conclude that ethylene and gibberellins do not seem to play a prominent role during these processes.