Genome-wide analysis of the maternal-to-zygotic transition in Drosophila primordial germ cells

Background: During the maternal-to-zygotic transition (MZT) vast changes in the embryonic transcriptome are produced by a combination of two processes: elimination of maternally provided mRNAs and synthesis of new transcripts from the zygotic genome. Previous genome-wide analyses of the MZT have been restricted to whole embryos. Here we report the first such analysis for primordial germ cells (PGCs), the progenitors of the germ-line stem cells. Results: We purified PGCs from Drosophila embryos, defined their proteome and transcriptome, and assessed the content, scale and dynamics of their MZT. Transcripts encoding proteins that implement particular types of biological functions group into nine distinct expression profiles, reflecting coordinate control at the transcriptional and posttranscriptional levels. mRNAs encoding germ-plasm components and cell-cell signaling molecules are rapidly degraded while new transcription produces mRNAs encoding the core transcriptional and protein synthetic machineries. The RNA-binding protein Smaug is essential for the PGC MZT, clearing transcripts encoding proteins that regulate stem cell behavior, transcriptional and posttranscriptional processes. Computational analyses suggest that Smaug and AU-rich element binding proteins function independently to control transcript elimination. Conclusions: The scale of the MZT is similar in the soma and PGCs. However, the timing and content of their MZTs differ, reflecting the distinct developmental imperatives of these cell types. The PGC MZT is delayed relative to that in the soma, likely because relief of PGC-specific transcriptional silencing is required for zygotic genome activation as well as for efficient maternal transcript clearance.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000305391700004&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Biotechnology & Applied MicrobiologyGenetics & HereditySCI(E)20ARTICLE2null1

The dependence of new particle formation rates on the interaction between cluster growth, evaporation, and condensation sink

New particle formation (NPF) is one of the major contributors to atmospheric aerosol number concentrations. The initial step of NPF includes the formation and growth of small clusters, their evaporation and loss to pre-existing particles (characterized by the condensation sink, CS). In the polluted atmospheric boundary layer, the high environmental CS suppresses NPF and it can work synergistically with evaporation to further reduce the NPF rates. In this study, to quantitatively include CS into NPF analysis, we make simplifications to the cluster balance equations and develop approximate equations for the NPF rates in the presence of pre-existing particles, which are applicable to nucleation mechanisms that can be represented by a nonbranched nucleation pathway. The developed equations show that the proportion of clusters that finally lead to new particle formation is given by the cluster-specific ratio of growth rate/CS | evaporation rate | growth rate. As a result, the cumulative product of this ratio for all clusters in the nucleation pathway determines the NPF rates. By comparing with benchmark cluster dynamics simulations of sulfuric acid-dimethylamine and sulfuric acid-ammonia nucleation systems, the developed equations were confirmed to give good estimates of the NPF rates and approximately capture the dependency of NPF rates on CS and nucleating vapor concentrations. The CS dependency predicted by the developed equations shows larger deviations from the simulations when the cluster evaporation rates are high, i.e., when the underlying assumptions of the equations are not satisfied. The equations were also found to be in good agreement with atmospheric NPF rates measured in long-term field observations in urban Beijing.Peer reviewe

CO2 emissions from karst cascade hydropower reservoirs: mechanisms and reservoir effect

Carbon dioxide (CO2) emissions from aquatic surface to the atmosphere has been recognized as a significant factor contributing to the global carbon budget and environmental change. The influence of river damming on the CO2 emissions from reservoirs remains poorly constrained. This is hypothetically due to the change of hydraulic retention time (HRT) and thermal stratification intensity of reservoirs (related to the normal water level, NWL). To test this hypothesis, we quantified CO2 fluxes and related parameters in eight karst reservoirs on the Wujiang River, Southwest China. Our results showed that there was a significant difference in the values of pCO2 (mean = 3205.7 μatm, SD = 2183.4 μatm) and δ13CCO2 (mean = −18.9‰, SD = 1.6‰) in the cascade reservoirs, suggesting that multiple processes regulate CO2 production. Moreover, the calculated CO2 fluxes showed obvious spatiotemporal variations, ranging from −9.0 to 2269.3 mmol m−2 d−1, with an average of 260.1 mmol m−2 d−1. Interestingly, the CO2 flux and δ13CCO2 from reservoirs of this study and other reservoirs around the world had an exponential function with the reservoir effect index (Ri, HRT/NWL), suggesting the viability of our hypothesis on reservoir CO2 emission. This empirical function will help to estimate CO2 emissions from global reservoirs and provide theoretical support for reservoir regulation to mitigate carbon emission

Traffic-related dustfall and NOx, but not NH3, seriously affect nitrogen isotopic compositions in soil and plant tissues near the roadside

Ammonia (NH3) emissions from traffic have received particular attention in recent years because of their important contributions to the growth of secondary aerosols and the negative effects on urban air quality. However, few studies have been performed on the impacts of traffic NH3 emissions on adjacent soil and plants. Moreover, doubt remains over whether dry nitrogen (N) deposition still contributes a minor proportion of plant N nutrition compared with wet N deposition in urban road environments. This study investigated the delta N-15 values of road dustfall, soil, moss, camphor leaf and camphor bark samples collected along a distance gradient from the road, suggesting that samples collected near the road have significantly more positive delta N-15 values than those of remote sites. According to the SIAR model (Stable Isotope Analysis in R) applied to dustfall and moss samples from the roadside, it was found that NH3 from traffic exhaust (8.8 +/- 7.1%) contributed much less than traffic-derived NO2 (52.2 +/- 10.0%) and soil N (39.0 +/- 13.8%) to dustfall bulk N; additionally, 68.6% and 31.4% of N in mosses near the roadside could be explained by dry N deposition (only 20.4 +/- 12.5% for traffic-derived NH3) and wet N deposition, respectively. A two-member mixing model was used to analyse the delta N-15 in continuously collected mature camphor leaf and camphor bark samples, which revealed a similarity of the delta N-15 values of plant-available deposited N to N-15-enriched traffic-derived NOx-N. We concluded that a relatively high proportion of N inputs in urban road environments was contributed by traffic-related dustfall and NOx rather than NH3. These information provide useful insights into reducing the impacts of traffic exhaust on adjacent ecosystems and can assist policy makers in determining the reconstruction of a monitoring network for N deposition that reaches the road level. (C) 2019 Elsevier Ltd. All rights reserved

Organic Acids in Sequential Volume-Based Rainwater Samples in Shanghai: Seasonal Variations and Origins

Organic acids were investigated in the rain sequence. Samples were collected in Shanghai (East China) over a one-year period using an automatic volume-based sequential rain sampler designed by ourselves. Organic acids significantly contributed (17.8 ± 10.2%) to the acidity of rainfall events in Shanghai. We observed that the concentration of each water-soluble ion in the sequential volume-based rainwater samples did not change significantly after the cumulative rainfall reached ~1.2 mm, on average. The volume-weighted mean (VWM) concentrations of formic acid, acetic acid, and oxalic acid were 13.54 μeq L−1, 8.32 μeq L−1, and 5.85 μeq L−1, respectively. Organic acids might mostly come from fine particles, which was the reason for the differences in acid concentrations in rainfall events, cloud water, and early sequences of rainfall events. The VWM concentrations of organic acids in rainfall events, cloud water, and early sequences of rainfall events were highest in spring and lowest in winter. Further analysis, including positive matrix factorization (PMF), suggested that vehicle exhaust and secondary emission sources were dominant contributors of organic acids in rainfall events (40.5%), followed by biological emission sources (37.3%), and biomass combustion sources (18.6%). The overall results not only reveal the critical role of organic acids in cloud water and rainfall events but also indicate organic acids might pose an ecological threat to the local surface ecosystem

Organic Acids in Sequential Volume-Based Rainwater Samples in Shanghai: Seasonal Variations and Origins

Organic acids were investigated in the rain sequence. Samples were collected in Shanghai (East China) over a one-year period using an automatic volume-based sequential rain sampler designed by ourselves. Organic acids significantly contributed (17.8 ± 10.2%) to the acidity of rainfall events in Shanghai. We observed that the concentration of each water-soluble ion in the sequential volume-based rainwater samples did not change significantly after the cumulative rainfall reached ~1.2 mm, on average. The volume-weighted mean (VWM) concentrations of formic acid, acetic acid, and oxalic acid were 13.54 μeq L−1, 8.32 μeq L−1, and 5.85 μeq L−1, respectively. Organic acids might mostly come from fine particles, which was the reason for the differences in acid concentrations in rainfall events, cloud water, and early sequences of rainfall events. The VWM concentrations of organic acids in rainfall events, cloud water, and early sequences of rainfall events were highest in spring and lowest in winter. Further analysis, including positive matrix factorization (PMF), suggested that vehicle exhaust and secondary emission sources were dominant contributors of organic acids in rainfall events (40.5%), followed by biological emission sources (37.3%), and biomass combustion sources (18.6%). The overall results not only reveal the critical role of organic acids in cloud water and rainfall events but also indicate organic acids might pose an ecological threat to the local surface ecosystem

Dissolved hydrolyzed amino acids in precipitation in suburban Guiyang, southwestern China: Seasonal variations and potential atmospheric processes

Proteinaceous compounds are particularly interesting because of their ubiquity and importance in many atmospheric processes. We investigated hydrolyzed amino acid (HAA), dissolved organic nitrogen (DON), nitrate (NO3-) and ammonium (NH4+) concentrations in precipitation samples collected in a suburban site in Guiyang over a 12 month period. Annually averaged total HAA, DON, NO3- and NH4+ concentrations were 3.7 mu mol L-1, 151.1 mu mol L-1, 68.9 mu mol L-1 and 117.3 mu mol L-1, respectively. Regarding the HAAs in precipitation, glutamic acid, glycine and proline were present in relatively high concentrations, followed by aspartic acid and alanine. The concentrations of total HAAs in precipitation showed a clear seasonal cycle, with a minimum level in winter and a maximum level in spring. Based on seasonal variations of total HAAs together with back-trajectory analysis, the air mass origins did not significantly impact the precipitation HAA levels. The NO3- concentrations recorded a better positive correlation (P < 0.01) with both the DON and total HAA concentrations than the NH4+ concentrations, possibly revealing that the sources for precipitation amino acids in suburban Guiyang were more linked with NO3- sources (from biomass burning, microbial activities and agricultural activities) than with NH4+ sources (from biomass burning and agricultural activities). In particular, in some specific periods, such as spring, abundant pollen releases may have been responsible for the relatively high precipitation amino acid concentrations. The average air temperature and the highest air temperature showed a positive correlation with the total HAA levels in precipitation. Clearly, the increase in precipitation total HAAs with higher air temperatures may indicate the enhanced temperature-induced degradation of high molecular weight atmospheric proteinaceous matter. Moreover, the volume-weighted precipitation glycine and total HAA levels were positively correlated with the product of atmospheric ozone and nitrogen dioxide, indicating that atmospheric proteinaceous matter may be inextricably bound up with both ozone- and nitrogen dioxide-related atmospheric processes. In conclusion, this study improves current knowledge on the origins and atmospheric processes of atmospheric proteinaceous compounds

Lipid biomarkers in suspended particulate matter and surface sediments in the Pearl River Estuary, a subtropical estuary in southern China

Lipid biomarkers in sediments in the Pearl River Estuary (PRE) have been studied in several previous studies, but little is known about their occurrence in the overlying water. Here, we determined the concentrations of lipids (n-alkanes, n-alkanols, sterols and fatty acids) in suspended particulate matter (SPM) in surface water and in sediments from the PRE. The data will improve our understanding of the sources, transport and sedimentation of lipids in estuarine environments. Our results showed that short-chain (C14-20) n-alkyl lipids contributed more than long-chain (C21-34) n-alkyl lipids to the total lipid concentrations in both SPM and sediments, suggesting aquatic plants and bacteria were the main contributors, whereas terrestrial organic matter (OM) were the minor contributors of n-alkyl lipids. It suggested that phytoplankton and bacteria contributing &gt; 65% to the n-alkyl lipids of SPM based on the three end-member mixing models. The concentrations of most lipids, except n-alkanes, decreased quickly in the low-salinity mixing zone and slowly decreased thereafter, with a transient slight increased when the salinity was 20-25, which would have been caused by variations of primary production in the aquatic system. In May, when rainfall was highest, lipids were characterized by a substantial contribution of terrestrial n-alkanes in the upstream SPM. Microbial activity and lipid degradation were found to occur in the water, and were most intense in the low-salinity mixing zone. Terrigenous lipids contributed more to the total lipid concentrations in sediments than in SPM, which demonstrated that terrigenous OM is relatively recalcitrant, and aquatic phytoplankton-derived OM is labile. (C) 2018 Elsevier B.V. All rights reserved

Variations in free amino acid concentrations in mosses and different parts of Cinnamomum camphora along an urban-to-rural gradient

Vegetation growing in urban ecosystems is frequently exposed to an environment with high atmospheric nitrogen (N) pollution. We systematically investigated the free amino acid concentrations in moss samples and Cinnamomum camphora leaf (new, middle-aged and old leaves), branch phloem, trunk phloem, and bark samples from field sites (Guiyang City, SW China) with different N deposition levels. The responses of the free amino acids to N deposition were analysed in the abovementioned plant tissues to determine whether plant free amino acids could act as biomarkers of the external N supply; moreover, differences in the N metabolism of these tissues under varying N deposition conditions were revealed by the compositions and sizes of their free amino acid pools. In particular, we reported the significant accumulation of arginine with increased N deposition in bark samples (while the arginine concentrations in the branch phloem, trunk phloem, and leaves remained low), which may indicate a long-term or historic external environment with a high N availability; additionally, the noticeable dominance and fluctuation of gamma-aminobutyric acid in response to varied N deposition levels occurred in both the branch phloem and the trunk phloem, suggesting that the gamma-aminobutyric acid transported in the phloem may be used as an important signal reflecting increases in the atmospheric N input. We conclude that the free amino acid concentrations in moss and camphor leaf, phloem and bark tissues are more sensitive to N deposition compared to their N concentrations and that tissue glutamine/glutamate and arginine/gamma-aminobutyric acid ratios may serve as better biomarkers reflecting the tissue N accumulation status associated with increased N deposition. Therefore, free amino acid concentration analyses of different plant parts may provide a means to gain a more in-depth understanding of the impacts of atmospheric N pollution on plant physiology and N cycles