Ectomycorrhizal fungal exoenzyme activity differs on spruce seedlings planted in forests versus clearcuts

Key message

Ectomycorrhizal (ECM) fungal community structure and potential exoenzymatic activity change after clearcut harvesting, but functional complementarity and redundancy among those ECM fungal species remaining support growth of regenerating seedlings.

Abstract

Ectomycorrhizal (ECM) fungal community composition is altered by forest harvesting, but it is not clear if this shift in structure influences ECM fungal physiological function at the community level. In this study, we characterized activities of extracellular enzymes in the ectomycorrhizospheres of Picea engelmannii seedlings grown in forest and clearcut plots. These exoenzymes are critical for the breakdown of large organic molecules, from which nutrients are subsequently absorbed and translocated by ECM fungi to host plants. We found that ectomycorrhizae on seedlings planted in forests had different exoenzyme activity profiles than those on seedlings planted in clearcuts. Specifically, the activities of glucuronidase, laccase, and acid phosphatase were higher on forest seedlings (P ≤ 0.006). These differences may have been partly driven by soil properties. Total carbon, total nitrogen (N), extractable phosphorus, extractable ammonium-N, and mineralizable N were higher, while pH was lower in forest plots (P ≤ 0.01). However, we also found that enzyme activity only shifted where community composition also changed. Functional complementarity can be inferred within ECM fungal communities in both forests and clearcuts because ectomycorrhizae formed by different species in the same environment had distinct enzyme profiles (P < 0.0001). However, ectomycorrhizae of Thelephora terrestris exhibited high levels of N- and P-mobilizing exoenzyme activities. Seedling biomass did not differ between forest and clearcut environments, so the high abundance of T. terrestris ectomycorrhizae in the clearcuts may have sustained nutrient acquisition by clearcut seedlings even in soils with lower N and P and with reduced ECM fungal species richness.

     

The P2-receptor-mediated Ca2+ signalosome of the human pulmonary endothelium - implications for pulmonary arterial hypertension

Purinergic Signalling - Dysfunction of the pulmonary endothelium is associated with most lung diseases. Extracellular nucleotides modulate a plethora of endothelial functions in the lung such as...     

A fundamental difference between macrobiota and microbial eukaryotes: protistan plankton has a species maximum in the freshwater-marine transition zone of the Baltic Sea

Remane's Artenminimum at the horohalinicum is a fundamental concept in ecology to describe and explain the distribution of organisms along salinity gradients. However, a recent metadata analysis challenged this concept for protists, proposing a species maximum in brackish waters. Due to data bias, this literature-based investigation was highly discussed. Reliable data verifying or rejecting the species minimum for protists in brackish waters were critically lacking. Here, we sampled a pronounced salinity gradient along a west–east transect in the Baltic Sea and analysed protistan plankton communities using high-throughput eDNA metabarcoding. A strong salinity barrier at the upper limit of the horohalinicum and 10 psu appeared to select for significant shifts in protistan community structures, with dinoflagellates being dominant at lower salinities, and dictyochophytes and diatoms being keyplayers at higher salinities. Also in vertical water column gradients in deeper basins (Kiel Bight, Arkona and Bornholm Basin) appeared salinity as significant environmental determinant influencing alpha- and beta-diversity patterns. Importantly, alpha-diversity indices revealed species maxima in brackish waters, that is, indeed contrasting Remane's Artenminimum concept. Statistical analyses confirmed salinity as the major driving force for protistan community structuring with high significance. This suggests that macrobiota and microbial eukaryotes follow fundamentally different rules regarding diversity patterns in the transition zone from freshwater to marine waters.     

Lysosomal Signaling Licenses Embryonic Stem Cell Differentiation via Inactivation of Tfe3

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Atmospheric photochemical transformations enhance 1,3-butadiene-induced inflammatory responses in human epithelial cells: The role of ozone and other photochemical degradation products

Chemistry of hazardous air pollutants has been studied for many years, yet little is known about how these chemicals, once reacted within urban atmospheres, affect healthy and susceptible individuals. Once released into the atmosphere, 1,3-butadiene (BD) reacts with hydroxyl radicals and ozone (created by photochemical processes), to produce many identified and unidentified products. Once this transformation has occurred, the toxic potential of atmospheric pollutants such as BD in the ambient environment is currently unclear. During this study, environmental irradiation chambers (also called smog chambers), utilizing natural sunlight, were used to create photochemical transformations of BD. The smog chamber/in vitro exposure system was designed to investigate the toxicity of chemicals before and after photochemical reactions and to investigate interactions with the urban atmosphere using representative in vitro samples. In this study, we determined the relative toxicity and inflammatory gene expression induced by coupling smog chamber atmospheres with an in vitro system to expose human respiratory epithelial cells to BD, BDs photochemical degradation products, or the equivalent ozone generated within the photochemical mixture. Exposure to the photochemically generated products of BD (primarily acrolein, acetaldehyde, formaldehyde, furan and ozone) induced significant increases in cytotoxicity, IL-8, and IL-6 gene expression compared to a synthetic mixture of primary products that was created by injecting the correct concentrations of the detected products from the irradiation experiments. Interestingly, exposure to the equivalent levels of ozone generated during the photochemical transformation of BD did not induce the same level of inflammatory cytokine release for either exposure protocol, suggesting that the effects from ozone alone do not account for the entire response in the irradiation experiments. These results indicate that BDs full photochemical product generation and interactions, rather than ozone alone, must be carefully evaluated when investigating the possible adverse health effects to BD exposures. The research presented here takes into account that photochemical transformations of hazardous air pollutants (HAPs) does generate a dynamic exposure system and therefore provides a more realistic approach to estimate the toxicity of ambient air pollutants once they are released into the atmosphere.     

Apoptosis regulates notochord development in Xenopus

The notochord is the defining characteristic of the chordate embryo and plays critical roles as a signaling center and as the primitive skeleton. In this study we show that early notochord development in Xenopus embryos is regulated by apoptosis. We find apoptotic cells in the notochord beginning at the neural groove stage and increasing in number as the embryo develops. These dying cells are distributed in an anterior to posterior pattern that is correlated with notochord extension through vacuolization. In axial mesoderm explants, inhibition of this apoptosis causes the length of the notochord to approximately double compared to controls. In embryos, however, inhibition of apoptosis decreases the length of the notochord and it is severely kinked. This kinking also spreads from the anterior with developmental stage such that, by the tadpole stage, the notochord lacks any recognizable structure, although notochord markers are expressed in a normal temporal pattern. Extension of the somites and neural plate mirrors that of the notochord in these embryos, and the somites are severely disorganized. These data indicate that apoptosis is required for normal notochord development during the formation of the anterior-posterior axis, and its role in this process is discussed.     

The sulfhydryl oxidase Erv1 is a substrate of the Mia40-dependent protein translocation pathway

The thiol oxidase Erv1 and the redox-regulated receptor Mia40/Tim40 are components of a disulfide relay system which mediates import of proteins into the intermembrane space (IMS) of mitochondria. Here we report that Erv1 requires Mia40 for its import into mitochondria. After passage across the translocase of the mitochondrial outer membrane Erv1 interacts via disulfide bonds with Mia40. Erv1 does not contain twin “CX₃C” or twin “CX₉C” motifs which are crucial for import of typical substrates of this pathway and it does not need two “CX₂C” motifs for import into mitochondria. Thus, Erv1 represents an unusual type of substrate of the Mia40-dependent import pathway.     

Noncompaction of the ventricular myocardium is associated with a de novo mutation in the beta-myosin heavy chain gene

Noncompaction of the ventricular myocardium (NVM) is the morphological hallmark of a rare familial or sporadic unclassified heart disease of heterogeneous origin. NVM results presumably from a congenital developmental error and has been traced back to single point mutations in various genes. The objective of this study was to determine the underlying genetic defect in a large German family suffering from NVM. Twenty four family members were clinically assessed using advanced imaging techniques. For molecular characterization, a genome-wide linkage analysis was undertaken and the disease locus was mapped to chromosome 14ptel-14q12. Subsequently, two genes of the disease interval, MYH6 and MYH7 (encoding the alpha- and beta-myosin heavy chain, respectively) were sequenced, leading to the identification of a previously unknown de novo missense mutation, c.842G>C, in the gene MYH7. The mutation affects a highly conserved amino acid in the myosin subfragment-1 (R281T). In silico simulations suggest that the mutation R281T prevents the formation of a salt bridge between residues R281 and D325, thereby destabilizing the myosin head. The mutation was exclusively present in morphologically affected family members. A few members of the family displayed NVM in combination with other heart defects, such as dislocation of the tricuspid valve (Ebstein's anomaly, EA) and atrial septal defect (ASD). A high degree of clinical variability was observed, ranging from the absence of symptoms in childhood to cardiac death in the third decade of life. The data presented in this report provide first evidence that a mutation in a sarcomeric protein can cause noncompaction of the ventricular myocardium.