Aims To assess the effects of atmospheric N deposition on the C budget of an alpine meadow ecosystem on the Qinghai-Tibetan Plateau, it is necessary to explore the responses of soil-atmosphere carbon dioxide (CO 2 ) exchange to N addition.Methods Based on a multi-form, low-level N addition experiment, soil CO 2 effluxes were monitored weekly using the static chamber and gas chromatograph technique. Soil variables and aboveground biomass were measured monthly to examine the key driving factors of soil CO 2 efflux.Results The results showed that low-level N input tended to decrease soil moisture, whereas medium-level N input maintained soil moisture. Three-year N additions slightly increased soil inorganic N pools, especially the soil NH 4 + -N pool. N applications significantly increased aboveground biomass and soil CO 2 efflux; moreover, this effect was more significant from NH 4 + -N than from NO 3 − -N fertilizer. In addition, the soil CO 2 efflux was mainly driven by soil temperature, followed by aboveground biomass and NH 4 + -N pool. Conclusions These results suggest that chronic atmospheric N deposition will stimulate soil CO 2 efflux in the alpine meadow on the Qinghai-Tibetan Plateau by increasing available N content and promoting plant growth.
Lung adenocarcinomas (LUAD) arise from precancerous lesions such as atypical adenomatous hyperplasia, which progress into adenocarcinoma in situ and minimally invasive adenocarcinoma, then finally into invasive adenocarcinoma. The cellular heterogeneity and molecular events underlying this stepwise progression remain unclear. In this study, we perform single-cell RNA sequencing of 268,471 cells collected from 25 patients in four histologic stages of LUAD and compare them to normal cell types. We detect a group of cells closely resembling alveolar type 2 cells (AT2) that emerged during atypical adenomatous hyperplasia and whose transcriptional profile began to diverge from that of AT2 cells as LUAD progressed, taking on feature characteristic of stem-like cells. We identify genes related to energy metabolism and ribosome synthesis that are upregulated in early stages of LUAD and may promote progression. MDK and TIMP1 could be potential biomarkers for understanding LUAD pathogenesis. Our work shed light on the underlying transcriptional signatures of distinct histologic stages of LUAD progression and our findings may facilitate early diagnosis.
To date, few studies are conducted to quantify the effects of reduced ammonium (NH4
+) and oxidized nitrate (NO3
−) on soil CH4 uptake and N2O emission in the subtropical forests. In this study, NH4Cl and NaNO3 fertilizers were applied at three rates: 0, 40 and 120 kg N ha−1 yr−1. Soil CH4 and N2O fluxes were determined twice a week using the static chamber technique and gas chromatography. Soil temperature and moisture were simultaneously measured. Soil dissolved N concentration in 0–20 cm depth was measured weekly to examine the regulation to soil CH4 and N2O fluxes. Our results showed that one year of N addition did not affect soil temperature, soil moisture, soil total dissolved N (TDN) and NH4
+-N concentrations, but high levels of applied NH4Cl and NaNO3 fertilizers significantly increased soil NO3
−-N concentration by 124% and 157%, respectively. Nitrogen addition tended to inhibit soil CH4 uptake, but significantly promoted soil N2O emission by 403% to 762%. Furthermore, NH4
+-N fertilizer application had a stronger inhibition to soil CH4 uptake and a stronger promotion to soil N2O emission than NO3
−-N application. Also, both soil CH4 and N2O fluxes were driven by soil temperature and moisture, but soil inorganic N availability was a key integrator of soil CH4 uptake and N2O emission. These results suggest that the subtropical plantation soil sensitively responses to atmospheric N deposition, and inorganic N rather than organic N is the regulator to soil CH4 uptake and N2O emission.
SUMMARYInsect hemocytes (blood cells) are a central part of the insect's cellular response to bacterial pathogens, and these specialist cells can both recognize and engulf bacteria. During this process, hemocytes undergo poorly characterized changes in adhesiveness. Previously, a peptide termed plasmatocyte-spreading peptide (PSP), which induces the adhesion and spreading of plasmatocytes on foreign surfaces, has been identified in lepidopteran insects. Here, we investigate the function of this peptide in the moth Manduca sexta using RNA interference (RNAi) to prevent expression of the precursor protein proPSP. We show that infection with the insect-specific bacterial pathogen Photorhabdus luminescens and non-pathogenic Escherichia coli induces proPSP mRNA transcription in the insect fat body but not in hemocytes; subsequently, proPSP protein can be detected in cell-free hemolymph. We used RNAi to silence this upregulation of proPSP and found that the knock-down insects succumbed faster to infection with P. luminescens, but not E. coli. RNAi-treated insects infected with E. coli showed a reduction in the number of circulating hemocytes and higher bacterial growth in hemolymph as well as a reduction in overall cellular immune function compared with infected controls. Interestingly, RNAi-mediated depletion of proPSP adversely affected the formation of melanotic nodules but had no additional effect on other cellular responses when insects were infected with P. luminescens, indicating that this pathogen employs mechanisms that suppress key cellular immune functions in M. sexta. Our results provide evidence for the central role of PSP in M. sexta cellular defenses against bacterial infections.
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Increased nitrogen (N) deposition has been found controversial affecting soil CO 2 emission in terrestrial ecosystems, which leads to serious debate on the efficiency of estimated C sequestration induced by N enrichment. The forms of input N might be responsible for this controversy. This study aims to explore the effects of NH 4 + (reduced N) and NO 3 − (oxidized N) on soil CO 2 flux and the underlying microbial mechanisms. An N addition experiment, two N fertilizers (NH 4 Cl and NaNO 3 ) and two rates (40 and 120 kg N ha −1 year −1 ), was carried out in a slash pine plantation of southern China. Soil-atmospheric CO 2 exchange, soil microbial biomass, and community composition were measured using static chamber-gas chromatography and phospholipid fatty acid (PLFA) analyses in the active growing and nonactive growing seasons, respectively. Low level of NaNO 3 addition significantly increased soil CO 2 flux in the active growing season, whereas other N treatments did not change soil CO 2 flux. High level of NH 4 Cl addition significantly reduced soil fungal biomass (fungal PLFA) and changed microbial community composition (ratio of fungal to bacterial (F/B) PLFAs). The positive relationships between the change in soil CO 2 flux and the change in fungal biomass, as well as between the change in soil CO 2 flux and the change in community composition, were observed in the nonactive growing season. The N forms as NO 3 − or NH 4 + are important factors affecting C cycles in the subtropical coniferous plantation. These results suggested that the variations of soil CO 2 emission and microbial biomass and community composition in the subtropical plantation depended on the seasons and the levels and forms of N addition.
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