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Soil inorganic nitrogen (N), i.e., NH4+ and NO3-, are essential resources for tree growth in forest ecosystems. Input of these inorganic resources are regulated by ammonification and nitrification and output are consumed either by abiotic or biotic (soil microbes, tree fine roots) processes. To the best of our knowledge, although previous studies have discussed net uptake rates of fine roots among different soil groups or vegetation types, variations within a local scale (same soil group and vegetation) remain an enigma. Moreover, since widely-used experiment set-ups in soil N transformation studies exclude live fine roots, uptake strategy of trees and their competition for inorganic nutrients with microbes are unknown. Therefore, this study aims to clarify 1) net uptake rates of fine roots; and 2) uptake strategy of the same tree species and the ratio of microbial/plant assimilation along a hillslope.An in situ incubation combining 15N tracing method with virtual soil cores was performed in Chamaecyparis obtusa (Japanese cypress) forests at up and down sites of a hillslope. 15N-labeled moieties (2.2 mg 15NH4NO3 g-1 soil and 0.2 mg NH415NO3g-1 soil, both are 98+ atom% 15N) were injected evenly through the cores located around the trees with five replicates. A-horizon soil was sampled after 0.25 h and 24 h. Soil and fine roots were sent for further analyses after sieving. The soil-environmental factors were determined.Differences in the soil-environmental variables were observed at up and down slopes, including soil pH, NH4+, NO3-, total dissolved N, microbial biomass carbon (C) and N, total C and C/N ratio. Fine root biomass was higher at up slope (1.5 kg m-3) than down slope (0.8 kg m-3) while net uptake rates of fine roots in both 15NH4NO3 (11 and 20 μg 15N g-1 roots d.w. d-1) and NH415NO3 (4.7 and 8.3 μg 15N g-1 roots d.w. d-1 at up and down slope, respectively) were higher at down slope. Ammonification and nitrification rates were also higher at down slope (0.6 and 3.2 mg N kg-1 d-1 for ammonification and 0.1 and 1.1 mg N kg-1 d-1 for nitrification at up and down slope, respectively), where soil pH was higher and C/N ratio was lower. However, net uptake amount per core did not demonstrate any trend at both slopes. Such results suggest that fine roots may try to ensure the supply of nutrients to trees by increasing their biomass when less soil inorganic N can be produced. Soil pH and C/N ratio could play a key role in determining uptake strategy of trees through affecting soil N transformation rates.In addition, the ratio of microbial/plant assimilation of N was higher at up slope for 15NH4+ and for 15NO3- to a lesser extent. Since soil moisture content was higher at down slope, such results might suggest a higher mass transfer of N nutrients induced by a higher mass flow of water. Therefore, higher N concentration could be maintained onto root surfaces at down slope, decreasing acquisition rates by microbes and increasing net uptake rates by fine roots.

Root fungal endophytes are present in most plants and co-occur with other mycorrhizal fungi. Their intraradical colonization suggests a special, differentiated relationship with host plants and increases opportunities for close interactions between hosts and fungal symbionts (e.g., carbon to nutrient exchange or hormone signalling). During the symbiosis between plant and arbuscular mycorrhizal fungi (AMF), specific trading features are established. These features have been incorporated into the biological market hypothesis, where dynamics of carbon to nutrient trading in the plant‐mycorrhizal fungal mutualism are compared to trades in a market economy. Multiple examples of similar dynamics have been shown for root endophytic fungi: soil nutrients are transported to the plant in exchange for carbon. However, plants have been shown to be able to reward AMF that exchange larger amount of nutrients (and vice versa), while at least some root fungal endophytes have been described as “by-product mutualists”, where the fungal symbiont enhances the performance and fitness of their host plant by providing benefits, but not requiring major investments from the host. Whereas AMF have received large attention, the role of fungal endophytes in carbon to nutrient exchange with plants remains largely uninvestigated.In this study we aimed at developing a controlled system to evaluate effects of multiple fungal endophytes (Colletotrichum tofieldiae and Cladophialophora chaetospira) on a model plant species (Lotus japonicus) and their role in the carbon to nitrogen exchange in the presence of different nitrogen sources (organic and inorganic). We further developed this controlled system to include plants colonized by AMF. Two-compartment petri dishes were used to achieve plant root colonization in a nutrient limited compartment and allow separation of nutrient sources only accessible by the fungal endophytes. We performed dual 15N and 13CO2 pulse-labelling experiments to trace the fate of plant carbon into fungal biomass and of different nitrogen sources into plant aboveground tissues. We analysed root for RNA sequencing to gain insights into the genetic controls over the observed dynamics.We successfully established a controlled system and found that C. tofieldiae can elicit positive effects on plant growth and nitrogen acquisition. These effects are dependent on the nutrient source to which the fungus has access to, with positive effects displayed in the presence of organic nitrogen. Plants exchange relatively less carbon to C. tofieldiae accessing organic nitrogen. Root transcriptome shows specific changes in response to root fungal colonization which are dependent on the nitrogen source available to the fungal endophyte. Furthermore, the presence of AMF did not modify the observed carbon to nitrogen exchange dynamics.In conclusion we show that the root fungal endophyte C. tofieldiae can play an important role for plant nutrient acquisition in the presence of organic nitrogen. The trade of nitrogen for plant carbon displays different features from the AMF symbiosis (i.e., higher amount of nitrogen is not rewarded with plant carbon investment) and different gene regulations are involved. Our results indicate complementarity between C. tofieldiae and AMF during root colonization, offering mechanistic explanations for the concomitant presence of AMF and fungal endophytes in terrestrial ecosystems.

Gastric cancer is anatomically proximal to peritoneum. Gastric cancer peritoneal metastasis is a complex biological process which is corresponded with disharmony within dysfunctional adipose tissue and metabolism reprogramming. Laminin gamma 1 (LAMC1) is highly expressed in cancer cells of peritoneal metastatic sites, however, the mechanism of LAMC1-metiated gastric cancer metastases to adipose tissue-rich peritoneum remains unclear. In our study, immunohistochemical staining, single cell sequencing, a co-culture model, luciferase reporter, RNA immunoprecipitation (RIP), Chromatin immunoprecipitation (CHIP) and single-molecular magnetic tweezers assays were conducted, and our results showed that LAMC1 related to Perilipin-1 content was highly expressed in peritoneal metastatic sites and mainly secreted by tumor cells. Gastric cancer cells secreted LAMC1 in an autocrine manner to detached from the primary site and promoted preadipocytes mature, rupture and release of free fatty acids (FFAs) in the peritoneal microenvironment to form pre-metastatic niche by the paracrine pathway. Reversely, differentiated preadipocyte-derived conditioned medium inhibited glycolysis and enhanced fatty acid oxidation (FAO) rate to promote cell proliferation, mesenchymal-epithelial transformation which led to tumor peritoneal colonization. In terms of biological mechanisms, one of differentiated preadipocyte-derived FFAs, palmitic acid-activated STAT3 inhibited miR-193a-3p by binding to its promoter directly; Using single-molecular magnetic tweezers, this binding manner was proved to be stable, reversable and ATP-dependent. Moreover, miR-193a-3p regulated LAMC1 in a post-translational manner. Furthermore, high LAMC1 expression in serum predicted a higher risk of peritoneal metastasis. In conclusion, our results illustrated that palmitic acid/p-STAT3/miR-193a-3p/LAMC1 pathway promotes preadipocyte differentiation, pre-metastatic niche formation and gastric cancer cell colonization to peritoneum.

Tropical regions are hotspots of increasing greenhouse gas emissions associated with land-use change. Although many field studies have quantified soil fluxes of nitrous oxide (N

Combined applications of plant residues and nitrogen (N) fertilizer in agroecosystems may increase N immobilization and reduce N loss through microbial propagation using fresh organic matter (FOM)....

Zhang W, Yang C, Wang S, et al. Cancer Manag Res. 2021;13:3601–3617. The authors have advised due to an error that occurred inadvertently at the time of figure assembly, Figure 5D on page 3609 is incorrect. The correct Figure 5 is shown in Download Article. The authors apologize for the error and advise it does not affect the results of the paper. Read the original article

Cropland intensification is needed to meet the demand for food in sub-Saharan Africa (SSA). This process requires a dramatic increase in resource inputs, including fertilizer-nitrogen (N) and organic residues (e.g., stover), which alter the soil-atmosphere exchange of nitrous oxide (N2O). The dearth of N2O emission data for SSA croplands, however, limits our ability to define regional and global N2O flux and mitigation opportunities. In two soils planted with maize in Tanzania (Iringa, sandy Alfisols; Mbeya, clayey Andisols), we conducted year-round measurements for 2 consecutive years to quantify N2O emissions in response to increasing N rates and in combination with maize stover incorporation. Rainfall and the resulting soil moisture, rather than soil temperature, were important environmental drivers of N2O emissions in these fields. Applied N stimulated N2O fluxes across soil types but with different magnitudes—lower in Iringa because of the dominance of nitrification in N2O production and higher in Mbeya likely from promoted denitrification when the water-filled pore space was >47%. N2O emission increased exponentially or linearly with N rate, depending on the year. The direct N2O emission factors were well below the 1% of the IPCC Tier 1 method, ranging from 0.13% to 0.26% in Iringa and from 0.24% to 0.42% in Mbeya, for a N rate of 50–150 kg N ha−1 during the study. Compared with N application alone, stover plus N did not significantly alter maize yield, but did raise N2O emissions significantly (P ≤ 0.06). Consequently, stover incorporation markedly increased the emission factor (up to 0.46% in Iringa and 1.29% in Mbeya) as well as yield-scaled N2O emissions. Our results suggest that linear and exponential emission responses can occur in SSA croplands and challenge the promotion of combining stover with fertilizer-N as resource input management in this region.

Weisong Zhang,* Chaogang Yang,* Shuyi Wang, Zhenxian Xiang, Rongzhang Dou, Zaihuan Lin, Jinsen Zheng, Bin Xiong Department of Gastrointestinal Surgery, Zhongnan Hospital of Wuhan University, Hubei Key Laboratory of Tumor Biological Behaviors & Hubei Cancer Clinical Study Center, Wuhan, 430071, People’s Republic of China*These authors contributed equally to this workCorrespondence: Bin Xiong Email binxiong1961@whu.edu.cnBackground: Detection of aberrant methylated DNA in the stool is an effective early screening method for colorectal cancer (CRC). Previously, reporters identified that syndecan-2 (SDC2) and tissue factor pathway inhibitor 2 (TFPI2) were aberrantly methylated in most CRC tissues. However, the combined diagnostic role of them remains undefined. Our research aimed at probing the role and efficiency of the methylation status of SDC2 and TFPI2 in CRC early screening by using bioinformatics analysis and clinical stool sample validation.Methods: The promoter and CpG site methylation levels of SDC2 and TFPI2 and their correlation with clinicopathological characteristics of CRC were analyzed using UALCAN, Methsurv, and Wanderer. UCSC Xena was used to perform survival analyses. LinkedOmics was used to do functional network analysis. DNA was isolated and purified from stool, and quantitative methylation-specific PCR (qMSP) was applied to detect methylatedSDC2 and TFPI2.Results: The results showed that promoter and most CpG site methylation levels of SDC2 and TFPI2 were significantly higher in CRC than in normal tissues. Moreover, SDC2 and TFPI2 methylation showed a positive correlation. Functional network analysis suggested that both methylated SDC2 and TFPI2 were involved in tumor cells’ metabolic programs. Besides, there was a higher positive integrated detection rate in CRC (n=61) with a sensitivity of 93.4% and in adenoma (Ade) (n=16) with a sensitivity of 81.3% than normal with a specificity of 94.3% in stool samples. What is more, integration of methylated SDC2 and TFPI2 showed a higher sensitivity and Youden index than a single gene in detecting Adeor CRC.Conclusion: Our data indicate that SDC2 and TFPI2 were hypermethylated in CRC, and integrated detection of methylated SDC2 and TFPI2 in stool has the potential to be an effective and noninvasive tool of CRC early screening.Keywords: DNA methylation, colorectal cancer, early detection, SDC2, TFPI2, stool

Dissimilatory nitrate (NO3−) reduction to ammonium (DNRA) and denitrification (DNF) are major dissimilatory NO3− reduction processes, competing for the available NO3− under anoxic conditions. The competition among these processes leads to different fates of NO3− in soil, i.e., loss of nitrogen (N) as benign N2 or potent greenhouse gas (nitrous oxide, N2O), or retaining of N by converting NO3− to ammonium. Unfortunately, little is known about the soil-environmental factors controlling the NO3− partition. Here we report DNF and DNRA in soils from the top and bottom of the hillslope.We sampled soils from a hillslope of forest to generate a soil-environmental gradient. The soil-environmental factors including soil pH, available carbon (potassium chloride-extractable organic carbon: EOC), NO3−, and microbial C and N (MBC and MBN) were determined. We incubated the soils under anoxic condition (i.e., helium atmosphere) and applied a 15N isotope pairing technique to quantify the potential rates of DNRA and DNF. Briefly, we incubated the soil under anoxic condition (i.e., helium atmosphere) to remove any N oxides and oxygen, then we added 15NO3− (99.9%) and measured the production rates of 15NH4+, 30N2, and 46N2O.The results showed that (1) a good gradient of the soil-environmental variables was observed along the hillslope from top to bottom, including pH (top–bottom; 3.95–4.78), EOC:NO3− (184–18.7), and MBC: MBN (8.2–6.3); (2) DNRA rate tended to be higher at the top of the hillslope with DNF being nearly inactive, resulting in a dominance of DNRA (59–97%), while the trend was reversed at the bottom, with DNF rates being much higher and dominantly contributing to NO3− reduction (89–97%); and (3) during DNF process, the magnitude of N2O production rates was comparable or even higher than that of N2 in the soils from the bottom of the hillslope. The ratio of the N2O to N2 production (N2O:N2) was much higher in the soils from the top despite the low DNF rates.The remarkably different patterns of DNRA and DNF rates and relative contributions between the top and bottom of the hillslope are controlled by the EOC:NO3−: DNRA was preferred over DNF when NO3− was limited (i.e., high EOC:NO3−) because more free energy is liberated per unit of NO3− reduced for DNRA as compared to DNF. The substantial production of N2O at the bottom of the hillslope indicates that previous studies that considered only 30N2 production rate could have highly underestimated the DNF rate. The high N2O:N2 at the top is likely caused by the low pH as well as the dominance of fungi, of which the N2O reductase is generally lacking, pointing to the key roles of soil pH and microbial community structure in regulating the product stoichiometry of N2O and N2 in DNF.

Enhancing crop production by maintaining a proper synchrony between soil nitrogen (N) and crop N demand remains a challenge, especially in under-studied tropical soils of Sub-Saharan Africa (SSA). For two consecutive cropping seasons (2013–2015), we monitored the fluctuation of soil inorganic N and its availability to maize in the Tanzanian highlands. Different urea-N rates (0–150 kg N ha−1; split into two dressings) were applied to two soil types (TZi, sandy Alfisols; and TZm, clayey Andisols). In the early growing season, soil mineralized N was exposed to the leaching risk due to small crop N demand. In the second N application (major N supply accounting for two-thirds of the total N), applied urea was more efficient in increasing soil inorganic N availability at TZm than at TZi. Such effect of soil type could be the main contributor to the higher yield at TZm (up to 4.4 Mg ha−1) than that at TZi (up to 2.6 Mg ha−1) under the same N rate. The best-fitted linear-plateau model indicated that the soil inorganic N availability (0–0.3 m) at the tasseling stage largely accounted for the final yield. Further, yields at TZi were still limited by N availability at the tasseling stage due to fast depletion of applied-N, whereas yields plateaued at TZm once N availability was above 67 kg N ha−1. Our results provided a valuable reference for designing the N management to increase yield, while minimizing the potentially adverse losses of N to the environment, in different agro-ecological zones in SSA.

Use of nitrogen (N) fertilizer is underway to increase in Sub-Saharan Africa (SSA). The effect of increasing N rates on ammonia (NH3) volatilization—a main pathway of applied-N loss in cropping systems—has not been evaluated in this region. In two soils (Alfisols, ALF; and Andisols, AND) with maize crop in the East African highlands, we measured NH3 volatilization following urea broadcast at six rates (0–150 kg N ha−1) for 17 days, using a semi-open static chamber method. Immediate irrigation and urea deep placement were tested as mitigation treatments. The underlying mechanism was assessed by monitoring soil pH and mineral N (NH4+ and NO3−) concentrations. More cumulative NH3-N was volatilized in ALF than in AND at the same urea-N rate. Generally, higher urea-N rates increased proportional NH3-N loss (percent of applied N loss as NH3-N). Based on well-fitted sigmoid models, simple surface urea application is not recommended for ALF, while up to 60 kg N ha−1 could be adopted for AND soils. The susceptibility of ALF to NH3 loss mainly resulted from its low pH buffering capacity, low cation exchange capacity, and high urease activity. Both mitigation treatments were effective. The inhibited rise of soil pH but not NH4+ concentration was the main reason for the mitigated NH3-N losses, although nitrification in the irrigation treatment might also have contributed. Our results showed that in acidic soils common to SSA croplands, proportional NH3-N loss can be substantial even at a low urea-N rate; and that the design of mitigation treatments should consider the soil’s inherent capacity to buffer NH3 loss.

Soil moisture and its spatial pattern are important for understanding various hydrological, pedological, ecological and agricultural processes. In this study, data of rainfall and soil moisture contents at different depths (10 cm, 20 cm, 40 cm and 60 cm) in forestland and vegetable plot in the Taihu Lake Basin, China were monitored and analyzed for characteristics of soil moisture variation and its response to several typical rainfall events. The following results were observed. First, great temporal variation of soil moisture was observed in the surface layer than in deeper layer in vegetable plot. In contrast, in forestland, soil moisture had similar variation pattern at different depths. Second, initial soil moisture was an important factor influencing the vertical movement of soil water during rainfall events. In vegetable plot, simultaneous response of soil moisture to rainfall was observed at 10- and 20-cm depths due to fast infiltration when initial soil was relatively dry. However, traditional downward response order occurred when initial soil was relatively wet. Third, critical soil horizon interface was an active zone of soil water accumulation and lateral movement. A less permeable W-B soil horizon interface (40-cm depth) in vegetable plot can create perched water table above it and elevate the soil water content at the corresponding depth. Fourth, the land cover was an effective control factor of soil moisture during small and moderate rainfall events. In the forestland, moderate and small rainfall events had tiny influences on soil moisture due to canopy and surface O horizon interception. Fifth, preferential flow and lateral subsurface interflow were important paths of soil water movement. During large and long duration rainfall events, lateral subsurface flow and preferential flow through surface crack or soil pipe occurred, which recharged the deep soil. However, in more concentrated large storm, surface crack or soil pipe connected by soil macropores was the main contributor to the occurrence of preferential flow. Findings of this study provide a theoretical foundation for sustainable water and fertilizer management and land use planning in the Taihu Lake Basin.

Nitrate (NO3−) leaching from agriculture is a growing environmental concern, but little attention has been given to the cropping systems in sub-Saharan Africa, where efforts are underway to increase fertilizer (especially nitrogen, N) use to secure food production. During 2015–2017, we monitored NO3− leaching from the critical root zone of maize in the tropical highlands of Tanzania using repacked soil monolith lysimeters. Four urea-N rates (0–150 kg N ha−1) and in combination with maize straw (∼2 Mg C ha−1; C:N ≥ 60) were evaluated in two soil types (sandy Alfisols and clayey Andisols). The soil rewetting process, particularly at the onset of the rainy season and following N applications, was a critical driver of NO3− flux. Nitrate leaching increased exponentially with increasing N rates, yet inter-annual variation was observed. Relating cumulative NO3− flux to maize yield under increasing N rates revealed a tipping point—occurrence depending on season—above which yield increments were accompanied by substantial NO3− leaching. Such a tipping point occurred at the N rate of 62 and 50 kg N ha−1 at the sandy and clayey site, respectively, in the second season. Straw incorporation induced net N immobilization in the early growing season, and reduced NO3− leaching by 3.3–6.3 kg N ha−1, but no effect was observed on the cumulative NO3− fluxes or maize yields. The NO3− leaching reductions (equivalent to 1.2–2.7 kg N Mg−1 C) were far below the net N immobilization potential of the incorporated straw (18.0–38.1 kg N Mg−1 C; for C:N ratios of 60–206). This was likely caused by large pieces of straw (∼0.15 m) used in the field, which reduced the surface area exposed to soil and microbes; consequently, only limited N in the decomposition microsites could be immobilized. Our results showed the potential to enhance maize yield without inducing substantial N leaching by adopting the proper N rate in the tropical highlands of Tanzania, and highlighted that temporary immobilization of leachable N by using large pieces of straw in the field was inefficient for the improvement of N synchrony and benefits to yield.