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BackgroundThe b-Zip transcription factor AtfA plays a key role in regulating stress responses in the filamentous fungus Aspergillus nidulans. To identify the core regulons of AtfA, we examined genome-wide expression changes caused by various stresses in the presence/absence of AtfA using A. nidulans microarrays. We also intended to address the intriguing question regarding the existence of core environmental stress response in this important model eukaryote.ResultsExamination of the genome wide expression changes caused by five different oxidative stress conditions in wild type and the atfA null mutant has identified a significant number of stereotypically regulated genes (Core Oxidative Stress Response genes). The deletion of atfA increased the oxidative stress sensitivity of A. nidulans and affected mRNA accumulation of several genes under both unstressed and stressed conditions. The numbers of genes under the AtfA control appear to be specific to a stress-type. We also found that both oxidative and salt stresses induced expression of some secondary metabolite gene clusters and the deletion of atfA enhanced the stress responsiveness of additional clusters. Moreover, certain clusters were down-regulated by the stresses tested.ConclusionOur data suggest that the observed co-regulations were most likely consequences of the overlapping physiological effects of the stressors and not of the existence of a general environmental stress response. The function of AtfA in governing various stress responses is much smaller than anticipated and/or other regulators may play a redundant or overlapping role with AtfA. Both stress inducible and stress repressive regulations of secondary metabolism seem to be frequent features in A. nidulans.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1705-z) contains supplementary material, which is available to authorized users.

High-frequency field potential activity between 50 and 400 Hz occurs throughout seizure-like events recorded from the CA3 region of juvenile rat hippocampal slices under low-[Mg(2+)] condition. Another (400-800 Hz) component occurred mainly during preictal paroxysmal spiking and the onsets of seizure-like events (97%) and less frequently during tonic and clonic phases (38% and 70%, respectively). Short epochs of oscillations in this range were associated with fast negative field potential deflections at the start of field potential transients. Voltage-clamp recordings from putative CA3 pyramidal cells showed the occurrence of synaptic inputs in the same frequency range at the onset of seizure-like events and the beginning of preictal or clonic paroxysmal spikes, while the frequency of action potentials never reached that range. The amplitude of fast negative field potential deflection, the rise time of membrane potential or voltage-clamp current changes and the mean phase coherence were consistent with an increase of synchronization towards the onset of a seizure-like event. Their parallel changes indicate the involvement of both synaptic and nonsynaptic mechanisms in the synchronization of neuronal activity and the development of seizure-like events in the low-[Mg(2+)] model of epilepsy.

BackgroundAspergillus fumigatus has to cope with a combination of several stress types while colonizing the human body. A functional interplay between these different stress responses can increase the chances of survival for this opportunistic human pathogen during the invasion of its host. In this study, we shed light on how the H2O2-induced oxidative stress response depends on the iron available to this filamentous fungus, using transcriptomic analysis, proteomic profiles, and growth assays.ResultsThe applied H2O2 treatment, which induced only a negligible stress response in iron-replete cultures, deleteriously affected the fungus under iron deprivation. The majority of stress-induced changes in gene and protein expression was not predictable from data coming from individual stress exposure and was only characteristic for the combination of oxidative stress plus iron deprivation. Our experimental data suggest that the physiological effects of combined stresses and the survival of the fungus highly depend on fragile balances between economization of iron and production of essential iron-containing proteins. One observed strategy was the overproduction of iron-independent antioxidant proteins to combat oxidative stress during iron deprivation, e.g. the upregulation of superoxide dismutase Sod1, the thioredoxin reductase Trr1, and the thioredoxin orthologue Afu5g11320. On the other hand, oxidative stress induction overruled iron deprivation-mediated repression of several genes. In agreement with the gene expression data, growth studies underlined that in A. fumigatus iron deprivation aggravates oxidative stress susceptibility.ConclusionsOur data demonstrate that studying stress responses under separate single stress conditions is not sufficient to understand how A. fumigatus adapts in a complex and hostile habitat like the human body. The combinatorial stress of iron depletion and hydrogen peroxide caused clear non-additive effects upon the stress response of A. fumigatus. Our data further supported the view that the ability of A. fumigatus to cause diseases in humans strongly depends on its fitness attributes and less on specific virulence factors. In summary, A. fumigatus is able to mount and coordinate complex and efficient responses to combined stresses like iron deprivation plus H2O2-induced oxidative stress, which are exploited by immune cells to kill fungal pathogens.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-4730-x) contains supplementary material, which is available to authorized users.

Gamma-amminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system of vertebrates, serves as an autocrine/paracrine signaling molecule during development, modulating a number of calcium (Ca(2+))-dependent processes, including proliferation, migration, and differentiation, acting via 2 types of GABA receptors (GABARs): ionotropic GABA(A)Rs and metabotropic GABA(B)Rs. Here, we demonstrate that mouse embryonic stem cells (mESCs), which possess the capacity for virtually unlimited self-renewal and pluripotency, synthesize GABA and express functional GABA(A)Rs and GABA(B)Rs, as well as voltage-gated calcium channels (VGCCs), ryanodine receptors (RyRs), and inwardly rectifying potassium (GIRK) channels. On activation, both GABAR types triggered synergistically intracellular calcium rise. Muscimol (a GABA(A)R agonist) induced single Ca(2+) transients involving both VGCC-mediated Ca(2+) influx and intracellular stores, while baclofen (a GABA(B)R agonist) evoked Ca(2+) transients followed by intercellular Ca(2+) waves and oscillations that were resistant to antagonists and entirely dependent on Ca(2+) release from intracellular stores. Prolonged treatment with muscimol slightly inhibited, while baclofen or SR95531 (a GABA(A)R antagonist) significantly facilitated, mESC proliferation. GABA(A)R-specific ligands also induced morphological and gene expression changes indicating a differentiation shift. Our data suggest that the interplay between GABARs and downstream (coupled) effectors differentially modulates mESC proliferation/differentiation through selective activation of second messenger signaling cascades.-Schwirtlich, M., Emri, Z., Antal, K., Máté, Z., Katarova, Z., Szabó, G. GABA(A) and GABA(B) receptors of distinct properties affect oppositely the proliferation of mouse embryonic stem cells through synergistic elevation of intracellular Ca(2+).