Brassinosteroid (BR) binding activates the receptor kinase BRI1 by inducing heterodimerization with its co-receptor kinase BAK1; however, the mechanisms that reversibly inactivate BRI1 remain unclear. Here we show that cytoplasm-localized protein phosphatase 2A (PP2A) B' regulatory subunits interact with BRI1 to mediate its dephosphorylation and inactivation. Loss-of-function and overexpression experiments showed that a group of PP2A B' regulatory subunits, represented by B'eta, negatively regulate BR signaling by decreasing BRI1 phosphorylation. BR increases the expression levels of these B' subunits, and B'eta interacts preferentially with phosphorylated BRI1, suggesting that the dynamics of BR signaling are modulated by the PP2A-mediated feedback inactivation of BRI1. Compared with PP2A B'alpha and B'beta, which promote BR responses by dephosphorylating the downstream transcription factor BZR1, the BRI1inactivating B' subunits showed similar binding to BRI1 and BZR1 but distinct subcellular localization. Alteration of the nuclear/ cytoplasmic localization of the B' subunits revealed that cytoplasmic PP2A dephosphorylates BRI1 and inhibits the BR response, whereas nuclear PP2A dephosphorylates BZR1 and activates the BR response. Our findings not only identify the PP2A regulatory B subunits that mediate the binding and dephosphorylation of BRI1, but also demonstrate that the subcellular localization of PP2A specifies its substrate selection and distinct effects on BR signaling.

The aim of this paper is to study the transport of nitrous oxide (N2O) from the Asian surface to the eastern Mediterranean Basin (MB). We used measurements from the spectrometer Thermal and Near infrared Sensor for carbon Observation Fourier transform spectrometer on board the Greenhouse gases Observing SATellite (GOSAT) over the period of 2010-2013. We also used the outputs from the chemical transport model LMDz-OR-INCA over the same period. By comparing GOSAT upper tropospheric retrievals to aircraft measurements from the High-performance Instrumented Airborne Platform for Environmental Research Pole-to-Pole Observations, we calculated a GOSAT High-performance Instrumented Airborne Platform for Environmental Research standard deviation (SD error) of similar to 2.0ppbv for a single pixel and a mean bias of approximately -1.3ppbv (approximately -0.4%). This SD error is reduced to similar to 0.1ppbv when we average the pixels regionally and monthly over the MB. The use of nitrogen fertilizer coupled with high soil humidity during the summer Asian monsoon produces high N2O emissions, which are transported from Asian surfaces to the eastern MB. This summertime enrichment over the eastern MB produces a maximum in the difference between the eastern and the western MB upper tropospheric N2O (east-west difference) in July in both the measurements and the model. N2O over the eastern MB can therefore be considered as a footprint of Asian summertime emissions. However, the peak-to-peak amplitude of the east-west difference observed by GOSAT (similar to 1.40.3ppbv) is larger than that calculated by LMDz-OR-INCA (similar to 0.8ppbv). This is due to an underestimation of N2O emissions in the model and to a relatively coarse spatial resolution of the model that tends to underestimate the N2O accumulation into the Asian monsoon anticyclone.

The existence of massive (10(11) solar masses) elliptical galaxies by redshift z approximate to 4 (refs 1-3; when the Universe was 1.5 billion years old) necessitates the presence of galaxies with star-formation rates exceeding 100 solar masses per year at z > 6 (corresponding to an age of the Universe of less than 1 billion years). Surveys have discovered hundreds of galaxies at these early cosmic epochs, but their star-formation rates are more than an order of magnitude lower(4). The only known galaxies with very high star-formation rates at z > 6 are, with one exception(5), the host galaxies of quasars(6-9), but these galaxies also host accreting supermassive (more than 10(9) solar masses) black holes, which probably affect the properties of the galaxies. Here we report observations of an emission line of singly ionized carbon ([C II] at a wavelength of 158 micrometres) in four galaxies at z > 6 that are companions of quasars, with velocity offsets of less than 600 kilometres per second and linear offsets of less than 100 kiloparsecs. The discovery of these four galaxies was serendipitous; they are close to their companion quasars and appear bright in the far-infrared. On the basis of the [C II] measurements, we estimate star-formation rates in the companions of more than 100 solar masses per year. These sources are similar to the host galaxies of the quasars in [C II] brightness, linewidth and implied dynamical mass, but do not show evidence for accreting supermassive black holes. Similar systems have previously been found at lower redshift(10-12). We find such close companions in four out of the twenty-five z > 6 quasars surveyed, a fraction that needs to be accounted for in simulations(13,14). If they are representative of the bright end of the [C II] luminosity function, then they can account for the population of massive elliptical galaxies at z approximate to 4 in terms of the density of cosmic space.

Elevated atmospheric nitrogen (N) depcisition has significantly influenced aquatic ecosystems, especially with regard to their N budgets and phytoplankton growth potentials. Compared to a considerable number of studies on oligotrophic lakes and oceanic waters, little evidence for the importance of N deposition has been generated for eutrophic lakes, even though emphasis has been placed on reducing external N inputs to control eutrophication in these lakes. Our high-resolution observations of atmospheric depositions and riverine inputs of biologically reactive N species into eutrophic Lake Dianchi (the sixth largest freshwater lake in China) shed new light onto the contribution of N deposition to total N loads. Annual N deposition accounted for 15.7% to 16.6% of total N loads under variable precipitation conditions, 2-fold higher than previous estimates (7.6%) for the Lake Dianchi. The proportion of N deposition to total N loads further increased to 27-48% in May and June when toxic blooms of the ubiquitous non-N-2 fixing cyanobacteria Microcystis spp. are initiated and proliferate. Our observations reveal that reduced N (59%) contributes a greater amount than oxidized N to total N deposition, reaching 56-83% from late spring to summer. Progress toward mitigating eutrophication in Lake Dianchi and other bloom-impacted eutrophic lakes will be difficult without reductions in ammonia emissions and subsequent N deposition.

Spatial patterns and temporal trends of nitrogen (N) and phosphorus (P) deposition are important for quantifying their impact on forest carbon (C) uptake. In a first step, we modeled historical and future change in the global distributions of the atmospheric deposition of N and P from the dry and wet deposition of aerosols and gases containing N and P. Future projections were compared between two scenarios with contrasting aerosol emissions. Modeled fields of N and P deposition and P concentration were evaluated using globally distributed in situ measurements. N deposition peaked around 1990 in European forests and around 2010 in East Asian forests, and both increased sevenfold relative to 1850. P deposition peaked around 2010 in South Asian forests and increased 3.5-fold relative to 1850. In a second step, we estimated the change in C storage in forests due to the fertilization by deposited N and P (Delta C-v (dep)), based on the retention of deposited nutrients, their allocation within plants, and C:N and C:P stoichiometry. Delta C-v (dep) for 1997-2013 was estimated to be 0.27 +/- 0.13 Pg C year(-1) from N and 0.054 +/- 0.10 Pg C year(-1) from P, contributing 9% and 2% of the terrestrial C sink, respectively. Sensitivity tests show that uncertainty of Delta C-v (dep) was larger from P than from N, mainly due to uncertainty in the fraction of deposited P that is fixed by soil. Delta C-P (dep) was exceeded by Delta C-N (dep) over 1960-2007 in a large area of East Asian and West European forests due to a faster growth in N deposition than P. Our results suggest a significant contribution of anthropogenic P deposition to C storage, and additional sources of N are needed to support C storage by P in some Asian tropical forests where the deposition rate increased even faster for P than for N.

We present an analysis of long-term (1988-2013; 26 years) total phosphorus (TP) concentration trends in 81 Swedish boreal lakes subject tominimal anthropogenic disturbance. Near universal increases in dissolved organic carbon (DOC) concentrations and a widespread but hitherto unexplained decline in TP were observed. Over 50% of the lakes (n = 42) had significant declining TP trends over the past quarter century (Sen's slope = 2.5% y(-1)). These declines were linked to catchment processes related to changes in climate, recovery from acidification, and catchment soil properties, but were unrelated to trends in P deposition. Increasing DOC concentrations appear to be masking in-lake TP declines. When the effect of increasing DOC was removed, the small number of positive TP trends (N = 5) turned negative and the average decline in TP increased to 3.9% y(-1). The greatest relative TP declines occurred in already nutrient poor, oligotrophic systems and TP concentrations have reached the analytical detection limit (1 mu L-1) in some lakes. In addition, ongoing oligotrophication may be exacerbated by increased reliance on renewable energy from forest biomass and hydropower. It is a cause of significant concern that potential impairments to lake ecosystem functioning associated with oligotrophication are not well handled by a management paradigm focused exclusively on the negative consequences of increasing phosphorus concentrations. (C) 2017 The Authors. Published by Elsevier B.V.

There is high uncertainty in the direct radiative forcing of black carbon (BC), an aerosol that strongly absorbs solar radiation. The observation-constrained estimate, which is several times larger than the bottom-up estimate, is influenced by the spatial representativeness error due to the mesoscale inhomogeneity of the aerosol fields and the relatively low resolution of global chemistry-transport models. Here we evaluated the spatial representativeness error for two widely used observational networks (AErosol RObotic NETwork and Global Atmosphere Watch) by downscaling the geospatial grid in a global model of BC aerosol absorption optical depth to 0.1 degrees x0.1 degrees. Comparing the models at a spatial resolution of 2 degrees x2 degrees with BC aerosol absorption at AErosol RObotic NETwork sites (which are commonly located near emission hot spots) tends to cause a global spatial representativeness error of 30%, as a positive bias for the current top-down estimate of global BC direct radiative forcing. By contrast, the global spatial representativeness error will be 7% for the Global Atmosphere Watch network, because the sites are located in such a way that there are almost an equal number of sites with positive or negative representativeness error.

Bright high-redshift quasars (z > 6) hosting supermassive black holes (M-BH > 10(8)M circle dot) are expected to reside in massive host galaxies embedded within some of the earliest and most massive galaxy overdensities. We analyze 1.2 mm ALMA dust continuum maps of 35 bright quasars at 6 < z < 7 and search the primary beam for excess dust continuum emission from sources with L-IR greater than or similar to 10(12) L circle dot as evidence for early protoclusters. We compare the detection rates of continuum sources at >= 5 sigma significance in the fields surrounding the quasars (A(eff).= 4.3 arcmin(2)) with millimeter number counts in blank field surveys. We discover 15 mm sources in the fields excluding the quasars themselves, corresponding to an overdensity of delta(gal) = (N-gal -N-exp)/N-exp= -0.07 +/- 0.56, consistent with no detected overdensity of dusty galaxies within 140 physical kpc of the quasars. However, the apparent lack of continuum overdensity does not negate the hypothesis that quasars live in overdense environments, as evidenced by strong [C II] overdensities found on the same scales as similarly selected quasars. The small field of view of ALMA could miss a true overdensity if it exists on scales larger than 1 cMpc, if the quasar is not centered in the overdensity, or if quasar feedback plays a role close to the quasar, but it is most likely that the large line-of-sight volume probed by a continuum survey will wash out a true overdensity signal. We discuss the necessary factors in determining the bias with which dusty star-forming galaxies trace true dark matter overdensities in order to improve upon overdensity searches in the dust continuum.

We present a survey of the [C II] 158 mu m line and underlying far-infrared (FIR) dust continuum emission in a sample of 27 greater than or similar to 6 quasars using the Atacama Large Millimeter Array (ALMA) at similar to 1 '' resolution. The [C II] line was significantly detected (at > 5-sigma) in 23 sources (85%). We find typical line luminosities of L-[C (II]) = 10(9-10) L-circle dot, and an average line width of similar to 385 km s(-1). The [C II]-to-far-infrared luminosity ratios ([C II]/FIR) in our sources span one order of magnitude, highlighting a variety of conditions in the star-forming medium. Four quasar host galaxies are clearly resolved in their [C II] emission on a few kpc scales. Basic estimates of the dynamical masses of the host galaxies give masses between 2 x 10(10) and 2 x 10(11) M-circle dot, i.e., more than an order of magnitude below what is expected from local scaling relations, given the available limits on the masses of the central black holes (> 3 x 10(8) M-circle dot, assuming Eddington-limited accretion). In stacked ALMA [C II] spectra of individual sources in our sample, we find no evidence of a deviation from a single Gaussian profile. The quasar luminosity does not strongly correlate with either the [C II] luminosity or equivalent width. This survey (with typical on-source integration times of 8 minutes) showcases the unparalleled sensitivity of ALMA at millimeter wavelengths, and offers a unique reference sample for the study of the first massive galaxies in the universe.

We present Atacama Large Millimeter Array 1 mm observations of the rest-frame far-infrared (FIR) dust continuum in 27 quasars at redshifts 6.0 less than or similar to z < 6.7. We detect FIR emission at greater than or similar to 3 sigma in all quasar host galaxies with flux densities at similar to 1900 GHz in the rest-frame of 0.12 < S-rest,S- (1900) (GHz) < 5.9 mJy, with a median (mean) flux density of 0.88 mJy (1.59 mJy). The implied FIR luminosities range from L-FIR = (0.27-13) x 10(12) L-circle dot, with 74% of our quasar hosts having L-FIR > 10(12) L-circle dot The estimated dust masses are M-dust = 10(7)-10(9) M-circle dot. If the dust is heated only by star formation, then the star formation rates in the quasar host galaxies are between 50 and 2700 M-circle dot yr(-1). In the framework of the host galaxy-black hole coevolution model a correlation between ongoing black hole growth and star formation in the quasar host galaxy would be expected. However, combined with results from the literature to create a luminosity-limited quasar sample, we do not find a strong correlation between quasar UV luminosity (a proxy for ongoing black hole growth) and FIR luminosity (star formation in the host galaxy). The absence of such a correlation in our data does not necessarily rule out the coevolution model, and could be due to a variety of effects (including different timescales for black hole accretion and FIR emission).