ALBERT

Description: A thin layer of fresh water from summer monsoon rain and river runoff in the Bay of Bengal (BoB) has profound influence on air-sea interaction across the south Asian region, but the mechanisms that sustain the low-salinity layer are as yet unknown. Using the first long time series of high-frequency observations from a mooring in the north BoB and satellite salinity data, we show that fresh water from major rivers is transported by large-scale flow and eddies, and shallow salinity stratification persists from summer through winter. The moored observations show frequent 0.2-1.2 psu salinity jumps with time scales of 10 minutes to days, due to O(1-10) km sub-mesoscale salinity fronts moving past the mooring. In winter, satellite sea surface temperature shows 10 km-wide filaments of cool water, in line with moored data. Rapid salinity and temperature changes at the mooring are highly coherent, suggesting slumping of salinity-dominated fronts. Based on these observations, we propose that sub-mesoscale fronts may be one of the important drivers for the persistent fresh layer in the north BoB.

Description: Oncostatin-M (OSM) is a patho-physiologically important pleiotropic, multifunctional cytokine. OSM mRNA sequence analysis revealed that its 3'UTR contains three highly conserved GC-rich cis -elements (GCREs) whose role in mRNA stability is unidentified. In the present study, the functional role of the proximal GC-rich region of osm 3'-UTR (GCRE-1) in post-transcriptional regulation of osm expression in U937 cells was assessed by transfecting construct containing GCRE-1 at 3' end of a fairly stable reporter gene followed by analysis of the expression of the reporter. GCRE-1 showed mRNA destabilizing activity however, upon PMA treatment the reporter message containing GCRE-1 was stabilized. This stabilization is owing to a time dependent progressive binding of trans -factors (atleast five proteins) to GCRE-1 post PMA treatment. Nucleolin was identified as one of the proteins in the RNP complex of GCRE-1 with PMA treated U937 cytosolic extracts by oligo-dT affinity chromatography of poly-adenylated GCRE-1. Immuno-blot revealed time dependent enhancement of nucleolin in the cytoplasm which in turn directly binds GCRE-1. RNA co-immunoprecipitation confirmed the GCRE-1-nucleolin interaction in-vivo . To elucidate the functional role of nucleolin in stabilization of osm mRNA, nucleolin was overexpressed in U937 cells and found to stabilize the intrinsic osm mRNA, where co-transfection with the reporter containing GCRE-1 confirms the role of GCRE-1 in stabilization of the reporter mRNA. Thus in conclusion, the results asserted that PMA treatment in U937 cells leads to cytoplasmic translocation of nucleolin that directly binds GCRE-1, one of the major GC-rich instability elements, thereby stabilizing the osm mRNA. This article is protected by copyright. All rights reserved

Description: ABSTRACT Transforming growth factor-β signaling exerts divergent effects on normal and cancer cells, although mechanism underlying this differential behavior remains unclear. In this study, expression of ninety-four genes pertaining to the TGF-β signaling pathway was compared between tumor and benign tissue samples from the human prostate gland to identify major discriminators driving prostate carcinogenesis. E2F5 was identified as one of the most deregulated genes in prostate cancer tissues, predominantly in samples with Gleason-score 6. Expression of other deregulated components of TGF-β signaling was examined by qRT-PCR, western blot and immune-staining. Function of E2F5 and p38 in prostate cancer was investigated using siRNA-treatment of PC3 cell-line followed by analyses of associated components and cell cycle. Observations revealed that E2F5 overexpression was accompanied by significantly higher phosphorylation of SMAD3 at Ser-208 in the linker region (pSMAD3L) and p38 in tumor tissue. A striking difference in SMAD3 phosphorylation, marked by preponderance of pSMAD3L and pSMAD3C (Ser-423 and 425) in tumor and benign tissues, respectively was noted. Co-localization of E2F5 with pSMAD3L in the nuclei of tumor and PC3 cells indicated a functional interface between the proteins. Downregulation of E2F5 and p38 in PC3 cells resulted in marked reduction of phosphorylation of SMAD3 and perturbation of cell cycle with an arrest of cells in G 1 . Our findings unearthed that E2F5/p38 axis played a cardinal role in uncontrolled cellular proliferation in prostate cancer through pSMAD3L activation. It also underscores a strong potential for E2F5 to be incorporated as a tool in early detection of prostate cancer. This article is protected by copyright. All rights reserved

Description: Abstract Microbial dynamics drive the biotic machinery of early soil evolution. However, integrated knowledge of microbial community establishment, functional associations, and community assembly processes in incipient soil is lacking. This study presents a novel approach of combining microbial phylogenetic profiling, functional predictions, and community assembly processes to analyze drivers of microbial community establishment in an emerging soil system. Rigorous submeter sampling of a basalt‐soil lysimeter after 2 years of irrigation revealed that microbial community colonization patterns and associated soil parameters were depth dependent. Phylogenetic analysis of 16S rRNA gene sequences indicated the presence of diverse bacterial and archaeal phyla, with high relative abundance of Actinomyceles on the surface and a consistently high abundance of Proteobacteria (Alpha, Beta, Gamma, and Delta) at all depths. Despite depth‐dependent variation in community diversity, predicted functional gene analysis suggested that microbial metabolisms did not differ with depth, thereby suggesting redundancy in functional potential throughout the system. Null modeling revealed that microbial community assembly patterns were predominantly governed by variable selection. The relative influence of variable selection decreased with depth, indicating unique and relatively harsh environmental conditions near the surface and more benign conditions with depth. Additionally, community composition near the center of the domain was influenced by high levels of dispersal, suggesting that spatial processes interact with deterministic selection imposed by the environment. These results suggest that for oligotrophic systems, there are major differences in the length scales of variation between vertical and horizontal dimensions with the vertical dimension dominating variation in physical, chemical, and biological features.

Description: Abstract Retarding potential analyzers are frequently flown on small satellites as in situ ion probes, from which can be derived a number of ion plasma parameters from a current‐voltage relationship (I‐V curve). The traditional method of analyzing retarding potential analyzer data produces inaccuracies in derived estimates when there is significant noise present in the instrument measurements. In this study we investigate the dependencies between parameters that produce uncertainties in noisy I‐V curves. It is found that multiple combinations of ion velocity and spacecraft floating potential can produce I‐V curves that lie within the noise envelope, which renders it difficult for a traditional curve fitting technique to objectively and accurately estimate parameters from a noisy I‐V curve. In this paper we propose BATFORD—a bootstrap resampling‐based technique to improve the accuracies of parameter estimates. It is particularly useful when signal‐to‐noise ratios are low. The algorithm is tested against a traditional curve fitting method for a simulated data set comprising I‐V curves for the middle‐ and low‐latitude ionosphere at low Earth orbit altitudes around 450 km, where O+ is the predominant species. BATFORD is found to provide more robust and reliable estimates assuming generalized noise distribution characteristics. As further validation, the algorithm is applied to satellite data from an orbit with deep plasma bubbles and hence low signal levels.

Description: Abstract The high temporal variability of the soil‐to‐atmosphere CO2 flux (soil respiration, RS) has been studied at hourly to multiannual timescales, but remains less well understood than RS spatial variability. How RS fluxes vary and are auto‐correlated at various time lags has practical implications for sampling, and more fundamentally for our understanding of its abiotic and biotic underlying mechanisms. We examined the variability, correlation, and sampling requirements of RS over a wide range of temporal scales in a temperate deciduous forest in eastern Maryland, USA, using both automated (temporally continuous, N = 30,036 over ten months) and survey (spatially diverse, temporally sparse, N = 1,912 over 17 months) data. Data from a global RS database were also used to examine interannual variability in comparable forests. The coefficient of variability of successive measurements generally varied from the minute (median CV 16%) to hourly and daily (11‐12%) timescales. Successive RS values measured at a given collar exhibited a strong hour‐to‐hour correlation (r = 0.931), and a moderate correlation at a two‐hour lag (0.289); day‐to‐day (i.e., 24 hour lag) hourly observations were uncorrelated. Daily RS means were well correlated at a one‐day lag (r = 0.856), but not at any further time lag. In a linear mixed‐effects model predicting RS, soil temperature and moisture exerted consistently strong effects regardless of timescale, and model coefficient of variability was generally high (〉80%). These results provide new opportunities to explore the drivers and variability of RS fluxes, quantify sampling requirements, and improve error propagation.

Description: Life history traits in many ectotherms show complex patterns of variation among conspecific populations sampled along wide latitudinal or climatic gradients. However, few studies have assessed whether these patterns can be explained better by thermal reaction norms of multiple life history traits, covering major aspects of the life cycle. In this study, we compared five populations of a Holarctic, numerically dominant soil microarthropod species, Folsomia quadrioculata , sampled from a wide latitudinal gradient (56–81°N), for growth, development, fecundity, and survival across four temperatures (10, 15, 20, and 25°C) in common garden experiments. We evaluated the extent to which macroclimate could explain differences in thermal adaptation and life history strategies among populations. The common garden experiments revealed large genotypic differences among populations in all the traits, which were little explained by latitude and macroclimate. In addition, the life history strategies (traits combined) hardly revealed any systematic difference related to latitude and macroclimate. The overall performance of the northernmost population from the most stochastic microclimate and the southernmost population, which remains active throughout the year, was least sensitive to the temperature treatments. In contrast, performance of the population from the most predictable microclimate peaked within a narrow temperature range (around 15°C). Our findings revealed limited support for macroclimate-based predictions, and indicated that local soil habitat conditions related to predictability and seasonality might have considerable influence on the evolution of life history strategies of F. quadrioculata . This study highlights the need to combine knowledge on microhabitat characteristics, and demography, with findings from common garden experiments, for identifying the key drivers of life history evolution across large spatial scales, and wide climate gradients. We believe that similar approaches may substantially improve the understanding of adaptation in many terrestrial ectotherms with low dispersal ability. A common garden approach was used to compare the differences in multiple postembryonic life history traits among conspecific populations of a soil-dwelling Collembolan species, which is widely distributed and numerically dominant across Holarctic. Our aim was to evaluate the extent of influence of macroclimate variables on the evolution of life history traits. We found trait-specific patterns of variation among population and limited support for macroclimate-driven evolution. Evidently, the life history strategies might be strongly affected by soil habitat conditions linked to seasonality and stochasticity at the sampling sites.

Description: Swimming organisms can enhance mixing in their natural environments by creating eddies in their wake and by dragging water along. However, these mixing mechanisms are inefficient for microorganisms, because swimming-induced variations in velocity, temperature and dissolved substances are evened out before they can be advected. In bioconvection, however, microorganisms induce water movement not by propulsion directly, but by locally changing the fluid density, which drives convection. Observations of bioconvection have so far mainly been limited to laboratory settings. We report the first observation and quantification of bioconvection within a stratified natural water body. Using in-situ measurements, laboratory experiments and simulations, we demonstrate that the bacterium Chromatium okenii is capable of mixing 0.3- to 1.2-m-thick water layers at around 12-m-water depth in the Alpine Lake Cadagno (Switzerland). As many species are capable of driving bioconvection, this phenomenon potentially plays a role in species distributions and influences large-scale phenomena like algal blooms.

Description: We develop an experimental daily surface heat flux dataset based on satellite observations to study subseasonal variability (periods shorter than 90 days) in the tropical Indian Ocean. We use incoming shortwave and longwave radiation from the International Satellite Cloud Climatology Project, and sea surface temperature (SST) from microwave sensors, to estimate net radiative flux. Latent and sensible heat fluxes are estimated from scatterometer winds and near-surface air temperature and specific humidity from Atmospheric Infrared Sounder (AIRS) observations calibrated to buoy data. Seasonal biases in net heat flux are generally within 10 Wm −2 of estimates from moorings, and the phases and amplitudes of subseasonal variability of heat fluxes are realistic. We find that the contribution of subseasonal changes in air-sea humidity gradients to latent heat flux equals or exceeds the contribution of subseasonal changes in wind speed in all seasons. SST responds coherently to subseasonal oscillations of net heat flux associated with active and suppressed phases of atmospheric convection in the summer hemisphere. Thus subseasonal SST changes are mainly forced by heat flux in the northeast Indian Ocean in northern summer, and in the 15 o S-5 o N latitude belt in southern summer. In the winter hemisphere, subseasonal SST changes are not a one-dimensional response to heat flux, implying that they are mainly due to oceanic advection, entrainment or vertical mixing. The coherent evolution of subseasonal SST variability and surface heat flux suggests active coupling between SST and large-scale, organized tropical convection in the summer season. This article is protected by copyright. All rights reserved.