A new model of Holocene peatland net primary production, decomposition, water balance, and peat accumulation

Peatland carbon and water cycling are tightly coupled, so dynamic modeling of peat accumulation over decades to millennia should account for carbon-water feedbacks. We present initial results from a new simulation model of long-term peat accumulation, evaluated at a wellstudied temperate bog in Ontario, Canada. The Holocene Peat Model (HPM) determines vegetation community composition dynamics and annual net primary productivity based on peat depth (as a proxy for nutrients and acidity) and water table depth. Annual peat (carbon) accumulation is the net balance above- and below-ground productivity and litter/peat decomposition – a function of peat hydrology (controlling depth to and degree of anoxia). Peat bulk density is simulated as a function of degree of humification, and affects the water balance through its influence on both the growth rate of the peat column and on peat hydraulic conductivity and the capacity to shed water. HPM output includes both time series of annual carbon and water fluxes, peat height, and water table depth, as well as a final peat profile that can be “cored” and compared to field observations of peat age and macrofossil composition. A stochastic 8500-yr, annual precipitation time series was constrained by a published Holocene climate reconstruction for southern Quebec. HPM simulated 5.4 m of ´ peat accumulation (310 kg C m−2 ) over 8500 years, 6.5% of total NPP over the period. Vascular plant functional types accounted for 65% of total NPP over 8500 years but only 35% of the final (contemporary) peat mass. Simulated age-depth and carbon accumulation profiles were compared to a radiocarbon dated 5.8 m, c.9000-yr core. The simulated core was younger than observations at most depths, but had a similar overall trajectory; carbon accumulation rates were generally higher in the simulation and were somewhat more variable than observations. HPM results were sensitive to centuryscale anomalies in precipitation, with extended drier periods (precipitation reduced ∼10%) causing the peat profile to lose carbon (and height), despite relatively small changes in NP

Add-on therapy options in asthma not adequately controlled by inhaled corticosteroids: a comprehensive review

Many patients with persistent asthma can be controlled with inhaled corticosteroids (ICS). However, a considerable proportion of patients remain symptomatic, despite the use of ICS. We present systematically evidence that supports the different treatment options. A literature search was made of Medline/PubMed to identify randomised and blinded trials. To demonstrate the benefit that can be obtained by increasing the dose of ICS, dose-response studies with at least three different ICS doses were identified. To demonstrate whether more benefit can be obtained by adding long-acting β(2)-agonist (LABA), leukotriene antagonist (LTRA) or theophylline than by increasing the dose of ICS, studies comparing these options were identified. Thirdly, studies comparing the different "add-on" options were identified. The addition of a LABA is more effective than increasing the dose of ICS in improving asthma control. By increasing the dose of ICS, clinical improvement is likely to be of small magnitude. Addition of a LTRA or theophylline to the treatment regimen appears to be equivalent to doubling the dose of ICS. Addition of a LABA seems to be superior to an LTRA in improving lung function. However, addition of LABA and LTRA may be equal with respect to asthma exacerbations. However, more and longer studies are needed to better clarify the role of LTRAs and theophylline as add-on therapies

Sydowia polyspora dominates fungal communities carried by two Tomicus species in pine plantations threatened by Fusarium circinatum

Producción CientíficaBark beetles (Coleoptera, Scolytinae) carry a diverse filamentous fungal community sometimes acting as vectors or carriers of phytopathogens. In this study, mycobiota carried by two Tomicus species (Tomicus piniperda and Tomicus destruens) were investigated through (i) morphological and molecular identification of taxa; (ii) taxonomic richness, diversity, evenness, dominance and phoresy indices; (iii) ecological network analysis and (iv) statistical co-occurrence analysis. The studied mycobiota were formed by eleven taxa and showed a moderate fungal diversity with low evenness. The fungus Sydowia polyspora was significantly abundant and dominated the community. All the fungal taxa were randomly associated. Both insect species (T. piniperda and T. destruens) were collected from plantations of Pinus radiata infected by Fusarium circinatum. The ecological factors that could drive community ecology and phoretic links between fungi and bark beetles are discussed.Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (project AGL2015-69370-R)Ministerio de Economía, Industria y Competitividad (project AGL2012-39912)Junta de Castilla y León - Fondo Europeo de Desarrollo Regional (grant ORDEN EDU/1083/2013

RNA-Dependent RNA Polymerase from Heterobasidion RNA Virus 6 Is an Active Replicase In Vitro

Heterobasidion RNA virus 6 (HetRV6) is a double-stranded (ds)RNA mycovirus and a member of the recently established genus Orthocurvulavirus within the family Orthocurvulaviridae. The purpose of the study was to determine the biochemical requirements for RNA synthesis catalyzed by HetRV6 RNA-dependent RNA polymerase (RdRp). HetRV6 RdRp was expressed in Escherichia coli and isolated to near homogeneity using liquid chromatography. The enzyme activities were studied in vitro using radiolabeled UTP. The HetRV6 RdRp was able to initiate RNA synthesis in a primer-independent manner using both virus-related and heterologous single-stranded (ss)RNA templates, with a polymerization rate of about 46 nt/min under optimal NTP concentration and temperature. NTPs with 2′-fluoro modifications were also accepted as substrates in the HetRV6 RdRp-catalyzed RNA polymerization reaction. HetRV6 RdRp transcribed viral RNA genome via semi-conservative mechanism. Furthermore, the enzyme demonstrated terminal nucleotidyl transferase (TNTase) activity. Presence of Mn2+ was required for the HetRV6 RdRp catalyzed enzymatic activities. In summary, our study shows that HetRV6 RdRp is an active replicase in vitro that can be potentially used in biotechnological applications, molecular biology, and biomedicine

RNA-Dependent RNA Polymerase from Heterobasidion RNA Virus 6 Is an Active Replicase In Vitro

Heterobasidion RNA virus 6 (HetRV6) is a double-stranded (ds)RNA mycovirus and a member of the recently established genus Orthocurvulavirus within the family Orthocurvulaviridae. The purpose of the study was to determine the biochemical requirements for RNA synthesis catalyzed by HetRV6 RNA-dependent RNA polymerase (RdRp). HetRV6 RdRp was expressed in Escherichia coli and isolated to near homogeneity using liquid chromatography. The enzyme activities were studied in vitro using radiolabeled UTP. The HetRV6 RdRp was able to initiate RNA synthesis in a primer-independent manner using both virus-related and heterologous single-stranded (ss)RNA templates, with a polymerization rate of about 46 nt/min under optimal NTP concentration and temperature. NTPs with 2′-fluoro modifications were also accepted as substrates in the HetRV6 RdRp-catalyzed RNA polymerization reaction. HetRV6 RdRp transcribed viral RNA genome via semi-conservative mechanism. Furthermore, the enzyme demonstrated terminal nucleotidyl transferase (TNTase) activity. Presence of Mn2+ was required for the HetRV6 RdRp catalyzed enzymatic activities. In summary, our study shows that HetRV6 RdRp is an active replicase in vitro that can be potentially used in biotechnological applications, molecular biology, and biomedicine

Characterization of VPS34-IN1, a selective inhibitor of Vps34, reveals that the phosphatidylinositol 3-phosphate-binding SGK3 protein kinase is a downstream target of class III phosphoinositide 3-kinase

The Vps34 (vacuolar protein sorting 34) class III PI3K (phosphoinositide 3-kinase) phosphorylates PtdIns (phosphatidylinositol) at endosomal membranes to generate PtdIns(3)P that regulates membrane trafficking processes via its ability to recruit a subset of proteins possessing PtdIns(3)P-binding PX (phox homology) and FYVE domains. In the present study, we describe a highly selective and potent inhibitor of Vps34, termed VPS34-IN1, that inhibits Vps34 with 25 nM ICin vitro, but does not significantly inhibit the activity of 340 protein kinases or 25 lipid kinases tested that include all isoforms of class I as well as class II PI3Ks. Administration of VPS34-IN1 to cells induces a rapid dose-dependent dispersal of a specific PtdIns(3)P-binding probe from endosome membranes, within 1 min, without affecting the ability of class I PI3K to regulate Akt. Moreover, we explored whether SGK3 (serum- and glucocorticoid-regulated kinase-3), the only protein kinase known to interact specifically with PtdIns(3)P via its N-terminal PX domain, might be controlled by Vps34. Mutations disrupting PtdIns(3)P binding ablated SGK3 kinase activity by suppressing phosphorylation of the T-loop [PDK1 (phosphoinositide-dependent kinase 1) site] and hydrophobic motif (mammalian target of rapamycin site) residues. VPS34-IN1 induced a rapid ~50-60% loss of SGK3 phosphorylation within 1 min. VPS34-IN1 did not inhibit activity of the SGK2 isoform that does not possess a PtdIns(3)P-binding PX domain. Furthermore, class I PI3K inhibitors (GDC-0941 and BKM120) that do not inhibit Vps34 suppressed SGK3 activity by ~40%. Combining VPS34-IN1 and GDC-0941 reduced SGK3 activity ~80-90%. These data suggest SGK3 phosphorylation and hence activity is controlled by two pools of PtdIns(3)P. The first is produced through phosphorylation of PtdIns by Vps34 at the endosome. The second is due to the conversion of class I PI3K product, PtdIns(3,4,5)P3 into PtdIns(3)P, via the sequential actions of the PtdIns 5-phosphatases [SHIP1/2 (Src homology 2-domain-containing inositol phosphatase 1/2)] and PtdIns 4-phosphatase [INPP4B (inositol polyphosphate 4-phosphatase type II)]. VPS34-IN1 will be a useful probe to delineate physiological roles of the Vps34. Monitoring SGK3 phosphorylation and activity could be employed as a biomarker of Vps34 activity, in an analogous manner by which Akt is used to probe cellular class I PI3K activity. Combining class I (GDC-0941) and class III (VPS34-IN1) PI3K inhibitors could be used as a strategy to better analyse the roles and regulation of the elusive class II PI3K

Successional change of testate amoeba assemblages along a space-for-time sequence of peatland development

It is well established that in ombrotrophic bogs, water-table depth (WTD) is the primary environmental control on testate amoeba distribution. However, the environmental controls on testate amoebae in minerotrophic fens are less well known and successional change in their assemblages associated with fen-bog peatland development has been scarcely investigated. Here we investigate a peatland space-for-time sequence resulting from postglacial rebound on the west coast of Finland, to assess successional patterns in testate amoeba communities and their relationships with environmental variables during peatland development. Sample sites along a 10-km transect from coast to inland ranged from a recently emerged wet meadow to a mature bog. Environmental variables (e.g., peat thickness, carbon and nitrogen content, pH, WTD and vegetation) were measured alongside testate amoeba samples. Results showed that even though the distribution of testate amoebae was to some extent determined by the succession stage, many taxa had wide WTD and pH ranges. The primary environmental control for many taxa changed along the succession. In conclusion, the ecological constraints on testate amoebae in minerotrophic systems are more complex than in bogs. The detected patterns also complicate the use of testate amoebae as a primary proxy in palaeoecological reconstructions where fen-to-bog shifts occur. (C) 2018 Elsevier GmbH. All rights reserved.Peer reviewe

Defoliation of Tilia cordata trees associated with Apiognomonia errabunda infection in Finland

We investigated the causative agent of a disease outbreak affecting small-leaved limes (Tilia cordata Mill.) and resulting in darkening of the leaf petioles and excessive defoliation during summer 2016 in southern Finland. The fungal species composition of the symptomatic petioles was examined by culture isolation and molecular identification using ITS rDNA sequences, which revealed the most prevalent fungal species present in the petioles as Apiognomonia errabunda (Roberge) Hhn. Based on reviewing curated herbarium specimens deposited at the Universities of Helsinki and Turku, A. errabunda is native and widely distributed in small-leaved limes in Finland, and occasionally infects also other broadleaved trees, including Quercus robur L. and ornamental species of Tilia L. and Fagus L. The ITS sequence analysis conducted during this study revealed minor within-species polymorphisms similar to those observed earlier in the Central European and Russian populations of A. errabunda, and reports the first nucleotide sequences of this species from the Nordic countries.Peer reviewe

Significance of Heterobasidion species among wood decay fungi in northern peatland forests

In Nordic countries, Heterobasidion root rot is known as a widespread and severe disease affecting conifer trees on mineral soils, while our understanding of its occurrence in peatland forests is more limited. This study investigated the prevalence of Heterobasidion parviporum and H. annosum, along with common coexisting fungi in disease centers, in six Norway spruce-dominated and two Scots pine-dominated drained peatland forests in southern Finland. Among the 590 trees examined, Heterobasidion species were the most common fungi responsible for root rot in both spruce and pine stands. In mature spruce stands, Heterobasidion sp. had infected an average of 5.4 trees per hectare, and in pine stands, 4.5 trees per hectare. However, our results showed that compared to mineral soils in the same region, Heterobasidion sp. was neither as frequent nor as dominant in Norway spruce stands on peat soil. Furthermore, the absence of large multi-tree Heterobasidion genets in peatland forests indicated restricted progression of Heterobasidion infections. Instead of Heterobasidion sp., Armillaria sp. was the predominant decay fungus in three spruce stands and one pine stand, while Resinicium bicolor was dominant in one spruce stand. Interestingly, Armillaria cepistipes, less pathogenic than A. borealis and rarely causing decay on spruce on mineral soil, was the most common Armillaria species at peatland sites. Further in-vitro-tests revealed that certain fungal isolates from the disease centers were highly competitive against H. parviporum. These isolates included both basidiomycetes, such as Stereum sanquinolentum and Amylostereum aerolatum, as well as the ascomycetes, Acocoryne sp., Leptodontidium elatius, and Rutstroemia calopus. Our findings led us to speculate that the competitive ability of Heterobasidion sp. against coexisting fungi might be lower in peatland conditions compared to mineral soils. Moreover, the potential risks and benefits of continuous cover forestry (CCF) regarding Heterobasidion root rot are discussed. Considering the relatively low prevalence of the pathogen in peatland forests and the more beneficial environmental effects of CCF compared to clear-cut-based rotation forestry, CCF appears to be a viable management option in spruce-dominated stands on drained peat soil. However, to ensure the health of peatland forests in the future, controlling Heterobasidion root rot is as crucial on peatland as it is on mineral sites

Identifying main uncertainties in estimating past and present radiative forcing of peatlands

ABSTRACT Reconstructions of past climate impact, i.e., radiative forcing (RF), of peatland carbon (C) dynamics show that immediately after peatland initiation the climate warming effect of CH4 emissions exceeds the cooling effect of CO2 uptake, but thereafter the net effect of most peatlands will move towards cooling, when RF switches from positive to negative. Reconstructing peatland C dynamics necessarily involves uncertainties related to basic assumptions on past CO2 flux, CH4 emission, and peatland expansion. We investigated the effect of these uncertainties on the RF of three peatlands, using either apparent C accumulation (aCAR), net C balance (NCB), or NCB plus C loss during fires as basis for CO2 uptake estimate; applying a plausible range for CH4 emission; and assuming linearly interpolated expansion between basal dates, or comparatively early or late expansion. When we factored that some C would only be stored temporarily (NCB and NCB+fire), the estimated past cooling effect of CO2 uptake increased but the present-day RF was affected little. Altering the assumptions behind the reconstructed CO2 flux or expansion patterns, caused the RF to peak earlier and advanced the switch from positive to negative RF by several thousand years. Compared to NCB, including fires had only small additional effect on RF lasting less than 1000 yr. The largest uncertainty in reconstructing peatland RF was associated with CH4 emissions. As shown by the consistently positive RF modelled for one site, and in some cases for the other two, peatlands with high CH4 emissions and low C accumulation rates may have remained climate warming agents since their initiation. Although uncertainties in present-day RF were mainly due to the assumed CH4 emission rates, the uncertainty in lateral expansion still had a significant effect on the present-day RF, highlighting the importance to consider uncertainties in the past peatland C balance in RF reconstructions.Reconstructions of past climate impact, that is, radiative forcing (RF), of peatland carbon (C) dynamics show that immediately after peatland initiation the climate warming effect of CH4 emissions exceeds the cooling effect of CO2 uptake, but thereafter the net effect of most peatlands will move toward cooling, when RF switches from positive to negative. Reconstructing peatland C dynamics necessarily involves uncertainties related to basic assumptions on past CO2 flux, CH4 emission and peatland expansion. We investigated the effect of these uncertainties on the RF of three peatlands, using either apparent C accumulation rates, net C balance (NCB) or NCB plus C loss during fires as basis for CO2 uptake estimate; applying a plausible range for CH4 emission; and assuming linearly interpolated expansion between basal dates or comparatively early or late expansion. When we factored that some C would only be stored temporarily (NCB and NCB+fire), the estimated past cooling effect of CO2 uptake increased, but the present-day RF was affected little. Altering the assumptions behind the reconstructed CO2 flux or expansion patterns caused the RF to peak earlier and advanced the switch from positive to negative RF by several thousand years. Compared with NCB, including fires had only small additional effect on RF lasting less than 1000 year. The largest uncertainty in reconstructing peatland RF was associated with CH4 emissions. As shown by the consistently positive RF modelled for one site, and in some cases for the other two, peatlands with high CH4 emissions and low C accumulation rates may have remained climate warming agents since their initiation. Although uncertainties in present-day RF were mainly due to the assumed CH4 emission rates, the uncertainty in lateral expansion still had a significant effect on the present-day RF, highlighting the importance to consider uncertainties in the past peatland C balance in RF reconstructions.Peer reviewe