Nitrogen deposition reduces the cover of biocrust-forming lichens and soil pigment content in a semiarid Mediterranean shrubland

Biocrusts are key drivers of the structure and functioning of drylands and are very sensitive to disturbance, including atmospheric nitrogen (N) deposition. We studied the impacts of simulated N deposition on biocrust community composition and soil photosynthetic and photoprotective pigment content after five years of N application in a European semiarid Mediterranean shrubland. The experiment consisted in six experimental blocks with four plots, each receiving 0, 10, 20, or 50 kg NH₄NO₃-N ha^-1 year^-1 + 6-7 kg N ha^-1 year^-1 background. After 5 years of N application, total lichen cover decreased up to 50% compared to control conditions and these changes were only clearly evident when evaluated from a temporal perspective (i.e. as the percentage of change from the first survey in 2008 to the last survey in 2012). In contrast, moss cover did not change in response to N, suggesting that biocrust community alterations operate via species- and functional group-specific effects. Interestingly, between-year variations in biocrust cover tracked variations in autumnal precipitation, showing that these communities are more dynamic than previously thought. Biocrust species alterations in response to N were, however, often secondary when compared to the role of ecologically relevant drivers such as soil pH and shrub cover, which greatly determined the composition and inter-annual dynamics of the biocrust community. Similarly, cyanobacterial abundance and soil pigment concentration were greatly determined by biotic and abiotic interactions, soil pH for pigments, and organic matter content and shrub cover for cyanobacteria. Biocrusts, and particularly the lichen component, are highly sensitive to N deposition and their responses to pollutant N can be best understood when evaluated from a temporal and multivariate perspective, including impacts mediated by interactions with biotic and abiotic drivers.

ScDREB8, a novel A-5 type of DREB gene in the desert moss Syntrichia caninervis, confers salt tolerance to Arabidopsis

Salinity is a major limitation factor for crop productivity worldwide. DREB transcription factors broadly participate in plant stress response and have been extensively identified in a wide variety of plants. In this study, we characterized and analyzed the function of a novel A-5 type DREB gene ScDREB8 from the desiccation tolerant moss Syntrichia caninervis. Yeast one-hybrid experiment showed that ScDREB8 had no transactivation activity. Transient expression assay in onion epidermal cells revealed that ScDREB8 is distributed throughout the cell with no apparent specificity. Overexpression of ScDREB8 significantly increased the germination rate of Arabidopsis under salt stress and improved the salt tolerance of Arabidopsis at the seedling stage by up-regulating the expression of downstream stress-related genes and improving ROS scavenging ability. ScDREB8 is a promising candidate gene for improving crop salt stress and will provide greater insight to the molecular mechanism of stress tolerance of A-5 type DREB proteins.

Epiphytic bryophytes as bio-indicators of atmospheric nitrogen deposition in a subtropical montane cloud forest: Response patterns, mechanism, and critical load

Increasing trends of atmospheric nitrogen (N) deposition due to pollution and land-use changes are dramatically altering global biogeochemical cycles. Bryophytes, which are extremely vulnerable to N deposition, often play essential roles in these cycles by contributing to large nutrient pools in boreal and montane forest ecosystems. To interpret the sensitivity of epiphytic bryophytes for N deposition and to determine their critical load (CL) in a subtropical montane cloud forest, community-level, physiological and chemical responses of epiphytic bryophytes were tested in a 2-year field experiment of N additions. The results showed a significant decrease in the cover of the bryophyte communities at an N addition level of 7.4 kg ha^-1 yr^-1, which is consistent with declines in the biomass production, vitality, and net photosynthetic rate responses of two dominant bryophyte species. Given the background N deposition rate of 10.5 kg ha^-1yr^-1 for the study site, a CL of N deposition is therefore estimated as ca. 18 kg N ha^-1 yr^-1. A disordered cellular carbon (C) metabolism, including photosynthesis inhibition and ensuing chlorophyll degradation, due to the leakage of magnesium and potassium and corresponding downstream effects, along with direct toxic effects of excessive N additions is suggested as the main mechanism driving the decline of epiphytic bryophytes. Our results confirmed the process of C metabolism and the chemical stability of epiphytic bryophytes are strongly influenced by N addition levels; when coupled to the strong correlations found with the loss of bryophytes, this study provides important and timely evidence on the response mechanisms of bryophytes in an increasingly N-polluted world. In addition, this study underlines a general decline in community heterogeneity and biomass production of epiphytic bryophytes induced by increasing N deposition.

Kinetics of 210Po accumulation in moss body profiles

Radionuclide concentration analysis of total moss bodies often gave relatively different results than a separate analysis of each different morphological part of the same sample. The dynamics of the transfer of metals by dust uplifted from the soil and another approach, based on the diffusion of the two radionuclides to the moss, have been analyzed. In the proposed model, short- and long-term approaches have been applied. Each part of a moss's profile can show different radionuclides accumulation ability, including both ²¹⁰Pb and ²¹⁰Po isotopes. A first-order kinetic model has been used for ²¹⁰Po and ²¹⁰Pb transport between three body components of mosses. This mathematical approach has been applied for ²¹⁰Po activity concentration in the air estimation. For relatively clean deep forest region, calculated concentrations were from 17.2 to 43.8 μBqm^-3, while for urban air concentrations were higher from 49.1 to 104.9 μBqm^-3.

Bryophyte gas-exchange dynamics along varying hydration status reveal a significant carbonyl sulphide (COS) sink in the dark and COS source in the light

Carbonyl sulphide (COS) is a potential tracer of gross primary productivity (GPP), assuming a unidirectional COS flux into the vegetation that scales with GPP. However, carbonic anhydrase (CA), the enzyme that hydrolyses COS, is expected to be light independent, and thus plants without stomata should continue to take up COS in the dark. We measured net CO₂ (A^C ) and COS (A^S ) uptake rates from two astomatous bryophytes at different relative water contents (RWCs), COS concentrations, temperatures and light intensities. We found large A^S in the dark, indicating that CA activity continues without photosynthesis. More surprisingly, we found a nonzero COS compensation point in light and dark conditions, indicating a temperature-driven COS source with a Q₁₀ (fractional change for a 10°C temperature increase) of 3.7. This resulted in greater A^S in the dark than in the light at similar RWC. The processes underlying such COS emissions remain unknown. Our results suggest that ecosystems dominated by bryophytes might be strong atmospheric sinks of COS at night and weaker sinks or even sources of COS during daytime. Biotic COS production in bryophytes could result from symbiotic fungal and bacterial partners that could also be found on vascular plants.

Genotoxic effect of Pb and Cd on in vitro cultures of Sphagnum palustre: An evaluation by ISSR markers

In the present work, the genotoxic effect of cadmium and lead supplied in a laboratory trial, was investigated for the first time in the moss Sphagnum palustre, by ISSR molecular markers. A total of 169 reproducible bands were obtained with 12 primers, ten of which gave polymorphisms (i.e., appearance/disappearance of bands), indicating a clear genotoxic effect induced by the metals. Both metals induced a decrease of the genome template stability in a dose dependent manner. At concentration >10^-5 Cd also induced a general toxic effect in S. palustre, leading to chlorophyll degradation and moss death. Moreover, we followed the fate of supplied heavy metals into the moss tissue by SEM-EDX to see if they entered the cells. SEM-EDX observations on moss cultures treated with equimolar concentrations of the two metals showed that most Pb precipitated in form of particles on moss surface, while Cd did not aggregate in particles and was not found on moss surface. In light of these findings, we concluded that probably Pb induced a genotoxic effect at lower intracellular concentrations than Cd.

Quantification of the overall measurement uncertainty associated with the passive moss biomonitoring technique: Sample collection and processing

In this study we examined 6080 data gathered by our research group during more than 20 years of research on the moss biomonitoring technique, in order to quantify the variability generated by different aspects of the protocol and to calculate the overall measurement uncertainty associated with the technique. The median variance of the concentrations of different pollutants measured in moss tissues attributed to the different methodological aspects was high, reaching values of 2851 (ng·g^-1)² for Cd (sample treatment), 35.1 (μg·g^-1)² for Cu (sample treatment), 861.7 (ng·g^-1)² and for Hg (material selection). These variances correspond to standard deviations that constitute 67, 126 and 59% the regional background levels of these elements in the study region. The overall measurement uncertainty associated with the worst experimental protocol (5 subsamples, refrigerated, washed, 5 × 5 m size of the sampling area and once a year sampling) was between 2 and 6 times higher than that associated with the optimal protocol (30 subsamples, dried, unwashed, 20 × 20 m size of the sampling area and once a week sampling), and between 1.5 and 7 times higher than that associated with the standardized protocol (30 subsamples and once a year sampling). The overall measurement uncertainty associated with the standardized protocol could generate variations of between 14 and 47% in the regional background levels of Cd, Cu, Hg, Pb and Zn in the study area and much higher levels of variation in polluted sampling sites. We demonstrated that although the overall measurement uncertainty of the technique is still high, it can be reduced by using already well defined aspects of the protocol. Further standardization of the protocol together with application of the information on the overall measurement uncertainty would improve the reliability and comparability of the results of different biomonitoring studies, thus extending use of the technique beyond the context of scientific research.

Arsenic in stream waters is bioaccumulated but neither biomagnified through food webs nor biodispersed to land

Human activities such as mining have contributed substantially to the increase of metals in aquatic environments worldwide. These metals are bioaccumulated by aquatic organisms and can be biomagnified along trophic webs. The dispersal of contaminants from water to land has been little investigated, even though most aquatic invertebrates in streams have aerial stages. We used field and laboratory approaches to investigate the effects of arsenic pollution on stream invertebrate assemblages, and its bioaccumulation, biomagnification and trophic transfer from aquatic to terrestrial environments by emergent insects. We conducted the study in an arsenic-impacted stream (40μgL^-1 As at the most polluted site) and a reference stream (0.3μgL^-1 As). Invertebrate abundance and richness were lowest at the most impacted site. Arsenic in biofilm and in invertebrates increased with the arsenic content in the water. The highest arsenic accumulators were bryophytes (1760μgg^-1), followed by the biofilm (449μgg^-1) and shredder invertebrates (313μgg^-1); predators had the lowest arsenic concentration. Insects emerging from water and spiders along streambanks sampled from the reference and the impacted stream did not differ in their body arsenic concentrations. In the laboratory, the shredder Sericostoma vittatum had reduced feeding rates when exposed to water from the impacted stream in comparison with the reference stream (15.6 vs. 19.0mg leaves mg body mass^-1 day^-1; p<0.05), but they grew faster in the polluted water (0.16±0.04% day^-1vs. 0.05±0.01% day^-1, p<0.05). S. vittatum exposed to contaminated stream water accumulated arsenic from food, not through contact with water. We concluded that although arsenic is bioaccumulated, mainly by food ingestion, it is not biomagnified through food webs and is not transported from the aquatic to terrestrial environment when insects leave the stream water.

Impacts of the removal of shrubs on the physiological and biochemical characteristics of Syntrichia caninervis Mitt: in a temperate desert

Moss crusts play important roles in biological soil crusts biomass and soil surface stabilization. However, because of increasingly intensive human activities, especially grazing, the growth and survival of shrubs are seriously threatened. This study aimed to test whether the presence of shrubs affects the physiological state of the bryophyte Syntrichia caninervis Mitt. in this desert ecosystem. We simulated animal-grazed shrubs at three levels in the Gurbantunggut Desert and compared these simulations to exposed areas, measuring the indicators of growth and stress tolerance exhibited by bryophytes. The results showed that the removal of shrubs significantly decreased chlorophyll fluorescence activity and soluble protein content in S. caninervis, especially under the total shrub removal treatment. The ratio between the total removal of shrubs and other treatments in antioxidative enzymes and in osmotic adjustment substances of S. caninervis exhibited two types of responses. With the exception of malonyldialdehyde (MDA) and superoxide dismutase (SOD), the variables examined fitted as downward parabolic then upward parabolic temporal dynamics. The removal of shrubs is harmful to the survival of S.caninervis. In resource-constrained conditions, SOD is an important antioxidant enzyme that of peroxidase (POD), catalase (CAT) and osmotic adjustment substances, for S. caninervis survival.

Comparison of headspace-oxylipin-volatilomes of some Eastern Himalayan mosses extracted by sample enrichment probe and analysed by gas chromatography-mass spectrometry

Mosses have an inherent adaptability against different biotic and abiotic stresses. Oxylipins, the volatile metabolites derived from polyunsaturated fatty acids (PUFAs), play a key role in the chemical defence strategy of mosses. In the present study, a comparative survey of these compounds, including an investigation into their precursor fatty acids (FAs), was carried out for the first time on the mosses Brachymenium capitulatum (Mitt.) Paris, Hydrogonium consanguineum (Thwaites & Mitt.) Hilp., Barbula hastata Mitt., and Octoblepharum albidum Hedw. collected from the Eastern Himalayan Biodiversity hotspot. Their headspace volatiles were sampled using a high-efficiency sample enrichment probe (SEP) and were characterized by gas chromatography-mass spectrometric analysis. FAs from neutral lipid (NL) and phospholipid (PL) fractions were also evaluated. Analysis of the oxylipin volatilome revealed the generation of diverse metabolites from C₅ to C₁₈, dominated by alkanes, alkenes, saturated and unsaturated alcohols, aldehydes, ketones and cyclic compounds, with pronounced structural variations. The C₆ and C₈ compounds dominated the total volatilome of all the samples. Analyses of FAs from membrane PL and storage NL highlighted the involvement of C₁₈ and C₂₀ PUFAs in oxylipin generation. The volatilome of each moss is characterized by a 'signature oxylipin mixture'. Quantitative differences in the C₆ and C₈ metabolites indicate their phylogenetic significance.

Quantitative assessment of metal elements using moss species as biomonitors in downwind area of lead-zinc mine

Distributions of a total of 21 elements were monitored in significantly lead-zinc polluted area using moss species (Hypnum cupressiforme and Camptothecium lutescens) used interchangeably, covering a denser sampling network. Interspecies comparison was conducted using Box-Cox transformed values, due to their skewed distribution. The median concentrations of trace elements in the both mosses examined decreased in the following order: Fe>Mn>Zn>Pb>Cu>Ni∼Cr∼As>Co>Cd>Hg. For almost all analyzed elements, H. cupressiforme revealed higher bio-accumulative abilities. For arsenic contents was obtained ER-value in favor of C. lutescens. The ER for the element contents according to the distance from the pollution source in selected areas was significantly enriched for the anthropogenic introduced elements As, Cd, Cu, Pb and Zn. After Box-Cox transformation of the content values, T_B was significantly different for As (4.82), Cd (3.84), Cu (2.95), Pb (4.38), and Zn (4.23). Multivariate factor analysis singled out four elemental associations: F1 (Al-Co-Cr-Fe-Li-Ni-V), F2 (Cd-Pb-Zn), F3 (Ca-Mg-Na-P) and F4 (Cu) with a total variance of 89%. Spatial distribution visualized the hazardously higher contents of "hot spots" of Cd > 1.30 mg/kg, Cu > 22 mg/kg, Pb > 130 mg/kg and Zn > 160 mg/kg. Therefore, main approach in moss biomonitoring should be based on data management of the element distribution by reducing the effect of extreme values (considering Box-Cox data transformation); the interspecies variation in sampling media does not deviate in relation to H. cupressiforme vs. C. lutescens.

The 'plant economic spectrum' in bryophytes, a comparative study in subalpine forest

PREMISE OF THE STUDY

Tradeoffs among functional traits of vascular plants are starting to be better understood, but it is unclear whether bryophytes possess similar tradeoffs or how trait relationships, or the 'economic spectrum', differ between the two groups.

METHODS

We determined functional-trait values [including shoot mass per area (SMA), light-saturated assimilation rate (A_mass), dark respiration rate (Rd_mass), N and P concentrations (N_mass and P_mass), and photosynthetic N and P use efficiency (PNUE and PPUE)] and their bivariate relationships for 28 bryophytes growing in a subalpine old-growth fir forest on the eastern Tibetan Plateau. Trait values and scaling relationships of these bryophytes were compared with data for vascular plant leaves from the Global Plant Trait Network (GLOPNET) dataset.

KEY RESULTS

We found that the A_mass, N_mass, N:P, PNUE and PPUE of bryophyte shoots were lower than those of vascular plant leaves. In contrast, bryophytes possessed higher P_mass and the two groups had similar values of SMA and Rd_mass. The N_mass and P_mass were closely associated with A_mass and Rd_mass, and these traits were all significantly negatively related to SMA. Metabolic rates increased faster with nutrient concentrations in bryophytes than in vascular plants.

CONCLUSIONS

Our research indicates that bryophytes have similar trait relationships as vascular plant leaves, although the slopes of the relationships differ for most trait combinations. This study confirms a functional-trait tradeoff in bryophytes, and reveals that bryophytes allocate greater proportions of N and P into the metabolic pools.

Tracking the route of phenanthrene uptake in mosses: An experimental trial

In recent decades, mosses have been used as native species or as transplants in monitoring a wide range of pollutants from inorganic (i.e. metals and metalloids) to organic contaminants (mainly polycyclic aromatic hydrocarbons-PAHs). To implement the use of mosses as biomonitors of PAHs, one important issue is the study of the interactions between these compounds and moss tissues. In this study we investigated the mode of phenanthrene uptake in four moss species (Amblystegium humile, Plagiomnium affine, Hypnum cupressiforme and a clone of Sphagnum palustre) and its movements from air to plant surface and within the biomonitors, using fluorescent and confocal microscopy. The target compound, partitioned between gas and particulate phase depending on air conditions, was selected since it is one of the most abundant PAHs released into the atmosphere. Our findings support the hypothesis that phenanthrene aggregates in particles and in this form it is chiefly intercepted and uptaken onto moss surfaces, albeit with different frequency in the four species, with S. palustre>H. cupressiforme>P. affine=A. humile. Phenanthrene enters the dead, empty hyalocysts of S. palustre. Specific surface area and composition, frequency and distribution of binding groups may also explain the different ability of phenanthrene uptake by the four moss species.

PCoM-DB Update: A Protein Co-Migration Database for Photosynthetic Organisms

The identification of protein complexes is important for the understanding of protein structure and function and the regulation of cellular processes. We used blue-native PAGE and tandem mass spectrometry to identify protein complexes systematically, and built a web database, the protein co-migration database (PCoM-DB, http://pcomdb.lowtem.hokudai.ac.jp/proteins/top), to provide prediction tools for protein complexes. PCoM-DB provides migration profiles for any given protein of interest, and allows users to compare them with migration profiles of other proteins, showing the oligomeric states of proteins and thus identifying potential interaction partners. The initial version of PCoM-DB (launched in January 2013) included protein complex data for Synechocystis whole cells and Arabidopsis thaliana thylakoid membranes. Here we report PCoM-DB version 2.0, which includes new data sets and analytical tools. Additional data are included from whole cells of the pelagic marine picocyanobacterium Prochlorococcus marinus, the thermophilic cyanobacterium Thermosynechococcus elongatus, the unicellular green alga Chlamydomonas reinhardtii and the bryophyte Physcomitrella patens. The Arabidopsis protein data now include data for intact mitochondria, intact chloroplasts, chloroplast stroma and chloroplast envelopes. The new tools comprise a multiple-protein search form and a heat map viewer for protein migration profiles. Users can compare migration profiles of a protein of interest among different organelles or compare migration profiles among different proteins within the same sample. For Arabidopsis proteins, users can compare migration profiles of a protein of interest with putative homologous proteins from non-Arabidopsis organisms. The updated PCoM-DB will help researchers find novel protein complexes and estimate their evolutionary changes in the green lineage.

Trace element concentrations in the moss Hypnum cupressiforme growing in a presumably unpolluted area

In this study we determined the concentrations of As, Cd, Hg, Ni and Pb in samples of the moss Hypnum cupressiforme collected during 5 different sampling surveys (2006-2014) in a presumably unpolluted area in northern Spain (25 sampling sites). We then applied factor analysis (FA) to the data to explore the factors underlying the spatial and temporal variability in the concentrations. The percentage of variance explained by the FA ranged between 34 and 98%, and was usually higher than 70%. The FA yielded 5 factors that explained the variance in the concentrations of Cd, As, Hg and Pb in all sampling surveys and also a single factor that explained the variance in Hg and Pb concentrations in 2006. Although the lack of obvious sources of pollution in the study region (at least for the elements considered) suggests that most elements (except perhaps Ni) probably originated from long-range atmospheric transport, this would not explain the results of the FA. We suggest that rather than being due to the origin of the pollutants (as frequently assumed), the spatio-temporal variability in the concentrations of these elements is probably determined by a series of other factors: the physicochemical characteristics of the pollutants and of the moss binding surfaces, physiological processes (e.g. moss growth), and the characteristics of the sampling sites (e.g. vegetation cover, elevation, slope, aspect). We therefore conclude that the assumption that variations in element concentrations in moss tissues are due to the origin of the pollutants is an oversimplification that leads to erroneous interpretation of the results of biomonitoring studies with terrestrial mosses.

Biomonitoring of air pollution using antioxidative enzyme system in two genera of family Pottiaceae (Bryophyta)

Bryophyte particularly mosses, have been found to serve as reliable indicators of air pollution and can serve as bryometers-biological instruments for measuring air pollution. They are remarkable colonizers, as they have the ability to survive in adverse environments and are also particular in their requirement of environmental conditions, which makes them appropriate ecological indicators. The purpose of this study was to evaluate the activity of antioxidative enzymes in two mosses viz., Hyophila rosea R.S. Williams and Semibarbula orientalis (Web.) Wijk. & Marg. and assess their suitability as biomonitors. Three different locations viz., Lucknow University, Residency (contaminated sites) and Dilkusha Garden (reference site) within Lucknow city with different levels of air pollutants were used for comparison. Our results indicate that air pollution caused marked enhancement in activity of antioxidative enzymes viz., catalase, peroxidase and superoxide dismutase. All the three are capable of scavenging reactive oxygen species. In the genus S. orientalis, catalase, peroxidase and superoxide dismutase activity was minimum at the reference site Dilkusha Garden and was significantly higher at the two contaminated sites for catalase and peroxidase, whereas the difference was non significant for superoxide dismutase. In H. rosea the activity of catalase and peroxidase at the three locations was almost similar, however superoxide dismutase activity showed a significant increase in the two contaminated sites when compared to the reference site, the value being highest for Lucknow University site. It was thus observed that the two genera, from the same location, showed difference in the activity of the antioxidative enzymes. Based on our results, we recommend bryophytes as good monitors of air pollution.

Uranium accumulation in aquatic macrophytes in an uraniferous region: Relevance to natural attenuation

Phytoremediation potential of uranium (U) was investigated by submerged, free-floating and rooted emergent native aquatic macrophytes inhabiting along the streams of Horta da Vilariça, a uraniferous geochemical region of NE Portugal. The work has been undertaken with the following objectives: (i) to relate the U concentrations in water-sediment-plant system; and (ii) to identify the potentialities of aquatic plants to remediate U-contaminated waters based on accumulation pattern. A total of 25 plant species culminating 233 samples was collected from 15 study points along with surface water and contiguous sediments. Concentrations of U showed wide range of variations both in waters (0.61-5.56 μg L(-1), mean value 1.98 μg L(-1)) and sediments (124-23,910 μg kg(-1), mean value 3929 μg kg(-1)) and this is also reflected in plant species examined. The plant species exhibited the ability to accumulate U several orders of magnitude higher than the surrounding water. Maximum U concentrations was recorded in the bryophyte Scorpiurium deflexifolium (49,639 μg kg(-1)) followed by Fontinalis antipyretica (35,771 μg kg(-1)), shoots of Rorippa sylvestris (33,837 μg kg(-1)), roots of Oenanthe crocata (17,807 μg kg(-1)) as well as in Nasturtium officinale (10,995 μg kg(-1)). Scorpiurium deflexifolium displayed a high bioconcentration factor (BF) of ∼2.5 × 10(4) (mean value). The species Fontinalis antipyretica, Nasturtium officinale (roots) and Rorippa sylvestris (shoots) exhibited the mean BFs of 1.7 × 10(4), 5 × 10(3) and 4.8 × 10(3) respectively. Maximum translocation factor (TF) was very much pronounced in the rooted perennial herb Rorippa sylvestris showing extreme ability to transport U for the shoots and seems to be promising candidate to be used as bioindicator species.

Organic nitrogen uptake is a significant contributor to nitrogen economy of subtropical epiphytic bryophytes

Without any root contact with the soil, epiphytic bryophytes must experience and explore poor, patchy, and heterogeneous habitats; while, the nitrogen (N) uptake and use strategies of these organisms remain uncharacterized, which obscures their roles in the N cycle. To investigate the N sources, N preferences, and responses to enhanced N deposition in epiphytic bryophytes, we carried out an in situ manipulation experiment via the (15)N labelling technique in an Asian cloud forest. Epiphytic bryophytes obtained more N from air deposition than from the bark, but the contribution of N from the bark was non-negligible. Glycine accounted for 28.4% to 44.5% of the total N in bryophyte tissue, which implies that organic N might serve as an important N source. Increased N deposition increased the total N uptake, but did not alter the N preference of the epiphytic bryophytes. This study provides sound evidence that epiphytic bryophytes could take up N from the bark and wet deposition in both organic and inorganic N forms. It is thus important to consider organic N and bark N sources, which were usually neglected, when estimating the role of epiphytic bryophytes in N cycling and the impacts of N deposition on epiphytic bryophytes in cloud forests.

Deciphering the Molecular Mechanisms Underpinning the Transcriptional Control of Gene Expression by Master Transcriptional Regulators in Arabidopsis Seed

In Arabidopsis (Arabidopsis thaliana), transcriptional control of seed maturation involves three related regulators with a B3 domain, namely LEAFY COTYLEDON2 (LEC2), ABSCISIC ACID INSENSITIVE3 (ABI3), and FUSCA3 (ABI3/FUS3/LEC2 [AFLs]). Although genetic analyses have demonstrated partially overlapping functions of these regulators, the underlying molecular mechanisms remained elusive. The results presented here confirmed that the three proteins bind RY DNA elements (with a 5'-CATG-3' core sequence) but with different specificities for flanking nucleotides. In planta as in the moss Physcomitrella patens protoplasts, the presence of RY-like (RYL) elements is necessary but not sufficient for the regulation of the OLEOSIN1 (OLE1) promoter by the B3 AFLs. G box-like domains, located in the vicinity of the RYL elements, also are required for proper activation of the promoter, suggesting that several proteins are involved. Consistent with this idea, LEC2 and ABI3 showed synergistic effects on the activation of the OLE1 promoter. What is more, LEC1 (a homolog of the NF-YB subunit of the CCAAT-binding complex) further enhanced the activation of this target promoter in the presence of LEC2 and ABI3. Finally, recombinant LEC1 and LEC2 proteins produced in Arabidopsis protoplasts could form a ternary complex with NF-YC2 in vitro, providing a molecular explanation for their functional interactions. Taken together, these results allow us to propose a molecular model for the transcriptional regulation of seed genes by the L-AFL proteins, based on the formation of regulatory multiprotein complexes between NF-YBs, which carry a specific aspartate-55 residue, and B3 transcription factors.

Metals in Pleurozium schreberi and Polytrichum commune from areas with various levels of pollution

Metals deposited into ecosystems are non-degradable and become one of the major toxic agents which accumulate in habitats. Thus, their concentration requires precise monitoring. To evaluate pollution around a chlor-alkali plant, a glass smelter, two power plants and a ceramic and porcelain factory, we selected terrestrial mosses with different life forms: the orthotropic and endohydric Polytrichum commune and plagiotropic and ectohydric Pleurozium schreberi. Metal concentrations were determined in both species growing together at sites situated at various distances approximately 0.75, 1.5, 3 and 6 km from polluters. MARS analysis evaluated different tendencies of both species for Cd, Co and Pb accumulation depending on the distance from the emitter. In P. schreberi, the concentration of these metals diminished relatively rapidly with an increasing distance from the emitter up to 3000 m and then stabilised. For P. commune, a steady decrease could be observed with increasing the distance up to 6000 m. PCCA ordination explained that both species from the vicinity of the chlor-alkali plant were correlated with the highest Co, Cr, Cu, Fe and Pb as well as Mn and Ni concentrations in their tissues. The mosses from sites closest to both power plants were correlated with the highest Cd and Zn concentrations. P. commune contained significantly higher Cd, Cr, Ni, Pb and Zn concentrations compared to P. schreberi. This may be caused by the lamellae found in the leaves of P. commune which increase the surface area of the possible aerial absorption of contaminants. Soil may also be an additional source of metals, and it affects the uptake in endohydric P. commune more than in ectohydric P. schreberi. However, the precise explanation of these relations needs further investigation.

Limited accumulation of copper in heavy metal adapted mosses

Copper is an essential micronutrient but has toxic effects at high concentrations. Bryophytes are remarkably tolerant to elevated levels of copper but we wondered if this tolerance might be species dependent. Therefore, in three moss species, Physcomitrella patens, Mielichhoferia elongata and Pohlia drummondii, the accumulation of copper was compared with semiquantitative SEM-EDX analyses after six weeks of cultivation on copper containing media. We investigated the role of the copper-linked anion and applied copper as CuCl2, CuSO4 and CuEDTA, respectively. Line scans along the growth axis of moss gametophores allowed for a detailed analysis of copper detection from the base towards the tip. Mosses originating from metal-containing habitats (i.e. M. elongata and P. drummondii) revealed a lower accumulation of copper when compared to the non-adapted P. patens. CuEDTA had a shielding effect in all three species and copper levels differed greatly from CuCl2 or CuSO4. The detection of reactive oxygen species (ROS), H2O2 and O2(-), was further used to indicate stress levels in the gametophore stems. ROS staining was increased along the whole stem and the tip in the non-adapted species P. patens whereas the tolerant species M. elongata and P. drummondii generally showed less staining located mainly at the base of the stem. We discuss the relation between metal accumulation and ROS production using indicator dyes in the three moss species. As moss gametophores are very delicate structures, ROS staining provide an excellent alternative to spectrophotometric analyses to estimate stress levels.

The evolutionary landscape of PRC1 core components in green lineage

The origin and evolution of plant PRC1 core components. Polycomb repressive complex1 (PRC1) plays critical roles in epigenetic silencing of homeotic genes and determination of cell fate. Animal PRC1 has been well investigated for a long time, whereas plant PRC1 was just confirmed in recent years. It is enigmatic whether PRC1 core components in plants share a common ancestor with those in animals. We evaluated the origin of plant PRC1 RING-finger proteins (RING1 and BMI1) through comparing with the homologs in some representative unikonts and using BMI1- and RING1-like proteins as reciprocal outgroup, finding both PRC1 RING-finger proteins have the earliest origin in mosses, similar to LHP1. Additionally, the gene structure, copy number, and domain organization were analyzed to deeply understand the evolutionary history of plant PRC1 complex. In conclusion, PRC1 RING-finger proteins have independent origins in plants and animals, but convergent evolution might attribute to the conservation of PRC1 complex in plants and animals. Plant LHP1 as the homolog of non-PRC1 protein HP1 was recruited to fulfill the role of Pc counterpart. Gene duplication followed by functional divergence makes a great contribution to evolutionary progress of PRC1 in green plants.

First survey of atmospheric heavy metal deposition in Kosovo using moss biomonitoring

Bryophytes act as bioindicators and bioaccumulators of metal deposition in the environment. The atmospheric deposition of Cd, Cr, Cu, Fe, Hg, Ni, Mn, Pb, and Zn in Kosovo was investigated by using carpet-forming moss species (Pseudocleropodium purum and Hypnum cupressiforme) as bioindicators. This research is part of the European moss survey coordinated by the ICP Vegetation, an International Cooperative Programme reporting on the effects of air pollution on vegetation to the UNECE Convention on Long-range Transboundary Air Pollution. Sampling was performed during the summer of 2011 at 25 sampling sites homogenously distributed over Kosovo. Unwashed, dried samples were digested by using wet digestion in Teflon tubes. The concentrations of metal elements were determined by atomic absorption spectrometry (AAS) equipped with flame and/or furnace systems. The heavy metal concentration in mosses reflected local emission sources. The data obtained in this study were compared with those of similar studies in neighboring countries and Europe (2010-2014 survey). The geographical distribution maps of the elements over the sampled territory were constructed using geographic information system (GIS) technology. The concentrations of Cr, Ni, Pb, and Zn were higher than the respective median values of Europe, suggesting that the zones with heavy vehicular traffic and industry emission input are important emitters of these elements. Selected zones are highly polluted particularly by Cd, Pb, Hg, and Ni. The statistical analyses revealed that a strong correlation exists between the Pb and Cd content in mosses, and the degree of pollution in the studied sites was assessed.

Nitrous oxide and methane emissions from cryptogamic covers

Cryptogamic covers, which comprise some of the oldest forms of terrestrial life on Earth (Lenton & Huntingford, ), have recently been found to fix large amounts of nitrogen and carbon dioxide from the atmosphere (Elbert et al., ). Here we show that they are also greenhouse gas sources with large nitrous oxide (N2 O) and small methane (CH4 ) emissions. Whilst N2 O emission rates varied with temperature, humidity, and N deposition, an almost constant ratio with respect to respiratory CO2 emissions was observed for numerous lichens and bryophytes. We employed this ratio together with respiration data to calculate global and regional N2 O emissions. If our laboratory measurements are typical for lichens and bryophytes living on ground and plant surfaces and scaled on a global basis, we estimate a N2 O source strength of 0.32-0.59 Tg year(-1) for the global N2 O emissions from cryptogamic covers. Thus, our emission estimate might account for 4-9% of the global N2 O budget from natural terrestrial sources. In a wide range of arid and forested regions, cryptogamic covers appear to be the dominant source of N2 O. We suggest that greenhouse gas emissions associated with this source might increase in the course of global change due to higher temperatures and enhanced nitrogen deposition.