Enhanced Nitrogen Uptake Research Articles

Foliar application of carbon dots enhances nitrogen uptake and assimilation through CEPD1-dependent signaling in plants

The use of nitrogen (N) fertilizers increases crop yield, but the accumulation of residual N in agricultural soils poses significant environmental risks. Improving the N use efficiency (NUE) of crops can help reduce N pollution. While nanomaterials have been shown to enhance crop agronomic traits, more research is needed to clarify the regulatory mechanisms involved. In this study, foliar spraying of carbon dots (CDs, 1 mg·mL−1) derived from Salvia miltiorrhiza increased the activity of plasma membrane H+-ATPase in Arabidopsis thaliana roots, promoting the uptake, transport, and assimilation of NO3- and NH4+. The upregulation of N metabolism-related genes, such as AtAMTs and AtNRTs, was also observed in A. thaliana roots. Transcriptome analysis suggested that this regulatory effect is mediated by the shoot-to-root mobile polypeptide CEPD1 (C-terminally encoded peptide DOWNSTREAM 1) signaling pathway. Additionally, foliar application of CDs increased the NUE of sweetpotato (Ipomoea batatas (L.) Lam.) from 2.5% to 8.1%. The upregulation of genes such as CEPD1 in leaves was observed following CDs application under different N conditions. Finally, foliar spraying of CDs significantly increased field yield and enhanced tolerance to low N stress in sweetpotato. Overall, this study demonstrated that foliar application of CDs improved NUE in plants through CEPD1-dependent signaling.

EARLY FLOWERING3-1 represses Grain number, plant height, and heading date7 to promote ABC1 REPRESSOR1 and regulate nitrogen uptake in rice.

The extensive use of nitrogen fertilizer boosts rice (Oryza sativa) production but also harms ecosystems. Therefore, enhancing crop nitrogen use efficiency is crucial. Here, we performed map-based cloning and identified the EARLY FLOWERING3 (ELF3) like protein-encoding gene OsELF3-1, which confers enhanced nitrogen uptake in rice. OsELF3-1 forms a ternary complex (OsEC) with OsELF4s and OsLUX, the putative orthologs of ELF4 and LUX ARRHYTHMO (LUX) in Arabidopsis (Arabidopsis thaliana), respectively. OsEC directly binds to the promoter of Grain number, plant height, and heading date7 (Ghd7) and represses its expression. Ghd7 encodes a transcription factor that has major effects on multiple agronomic traits. Ghd7 is also a transcriptional repressor and directly suppresses the expression of ABC1 REPRESSOR1 (ARE1), a negative regulator of nitrogen use efficiency. Therefore, targeting the OsEC-Ghd7-ARE1 module offers an approach to enhance nitrogen uptake, presenting promising avenues for sustainable agriculture.

Melatonin promotes nodule development enhancing soybean nitrogen metabolism under low nitrogen levels

Nitrogen availability profoundly impacts crop productivity, especially for soybeans, which exhibit a substantial demand for nitrogen. In response to the over-reliance on nitrogen fertilizers, which poses both inefficiencies and environmental concerns, the potential of melatonin in enhancing nitrogen uptake and utilization in soybeans through root irrigation was investigated. Melatonin significantly increased the activity of ammonium assimilating enzymes, thereby enhancing plant tolerance to low nitrogen levels, particularly at a concentration of 10 μM. This phenomenon has been conclusively linked to the augmented nitrogen fixation and utilization capacity, attributed to the facilitating rhizobial infection. Notably, melatonin influenced flavonoid content, specifically inducing genistein levels, essential for rhizobial infection. The malonyltransferase-encoding gene GmMaT2, which modifies isoflavones, was found to be crucial for the effects of melatonin on nodulation and nitrogen metabolism. The silence of GmMaT2 hindered the beneficial effects of melatonin on nodule development and attenuated its ability to enhance aspects of low nitrogen tolerance in soybean. It was elucidated that the potential of melatonin as a sustainable strategy for enhancing nitrogen utilization efficiency in soybeans. It provided insights into the underlying mechanisms and underscored the significance of GmMaT2 in mediating the beneficial effects induced by melatonin under low nitrogen conditions. The findings present a promising solution for mitigating agricultural costs and environmental impacts.

Efficacy of Nano Urea on Nitrogen Use Efficiency of Irrigated Maize under Temperate Ecology

A field experiment was conducted during the Kharif-2022 season at the Agronomy Research Field, FOA, SKUAST-Kashmir, to investigate the efficacy of nano-urea in improving nitrogen-use efficiency in irrigated maize. Ten treatments were evaluated viz., T1: Control, T2: Recommended dose of Nitrogen (RDN) as basal (prilled urea), T3: 75% RDN + 1 spray nano-urea at 2 ml L-1 (60 DAS), T4: 75% RDN + 1 spray at 4 ml L-1 (60 DAS), T5: 50% RDN + 2 sprays at 2 ml L-1 (30 and 60 DAS), T6: 50% RDN + 2 sprays at 4 ml L-1 (30 and 60 DAS), T7: 25% RDN + 2 sprays at 6 ml L-1 (30 and 60 DAS), T8: 25% RDN + 2 sprays at 8 ml L-1 (30 and 60 DAS), T9: 25% RDN + 1 spray at 6 ml L-1 (60 DAS), T10: 25% RDN + 1 spray at 8 ml L-1 (60 DAS). The experiment was carried out following a randomized complete block design with three replications. Results revealed that treatment T6 (50% RDN as basal + 2 sprays at 30 and 60 DAS at 4 ml L-1 of nano-urea) exhibited superior performance compared to the recommended nitrogen dose (T2) and other treatments in enhancing nutri-ent-use efficiency. Notably, treatment T6 demonstrated the highest nitrogen uptake in grain (101.92 kg ha-1) as well as stover (67.41 kg ha-1), surpassing all other treatments. Additionally, agronomic efficiency was significantly higher in T8, while physiological efficiency peaked in T6. Yield attributes and overall yield showed consistent improvements in treatments receiving nano-urea. Furthermore, treatments utilizing nano-urea demonstrated higher net returns and benefit-cost ratios, with T6 particularly standing out. These findings underscore the potential of foliar application of nano-urea to halve the recommended dose of prilled urea, thereby enhancing nitrogen uptake, nutrient-use efficiency, yield, and economic returns, while promoting sustainability in agriculture.

Exogenous GA3 Enhances Nitrogen Uptake and Metabolism under Low Nitrate Conditions in 'Duli' (Pyrus betulifolia Bunge) Seedlings.

'Duli' (Pyrus betulifolia Bunge) is one of the main rootstocks of pear trees in China. Gibberellin (GA) is a key plant hormone and the roles of GA in nitrate (NO3-) uptake and metabolism in plants remain unclear. In this study, we investigated the effects of exogenous GA3 on the N metabolism of 'Duli' seedlings under NO3- deficiency. The results showed that exogenous GA3 significantly improves 'Duli' growth under NO3- deficiency. On the one hand, GA3 altered the root architecture, increased the content of endogenous hormones (GA3, IAA, and ZR), and enhanced photosynthesis; on the other hand, it enhanced the activities of N-metabolizing enzymes and the accumulation of N, and increased the expression levels of N absorption (PbNRT2) and the metabolism genes (PbNR, PbGILE, PbGS, and PbGOGAT). However, GA3 did not delay the degradation of chlorophyll. Paclobutrazol had the opposite effect on growth. Overall, GA3 can increase NO3- uptake and metabolism and relieve the growth inhibition of 'Duli' seedlings under NO3- deficiency.

The elite haplotype OsGATA8-H coordinates nitrogen uptake and productive tiller formation in rice

Excessive nitrogen promotes the formation of nonproductive tillers in rice, which decreases nitrogen use efficiency (NUE). Developing high-NUE rice cultivars through balancing nitrogen uptake and the formation of productive tillers remains a long-standing challenge, yet how these two processes are coordinated in rice remains elusive. Here we identify the transcription factor OsGATA8 as a key coordinator of nitrogen uptake and tiller formation in rice. OsGATA8 negatively regulates nitrogen uptake by repressing transcription of the ammonium transporter gene OsAMT3.2. Meanwhile, it promotes tiller formation by repressing the transcription of OsTCP19, a negative modulator of tillering. We identify OsGATA8-H as a high-NUE haplotype with enhanced nitrogen uptake and a higher proportion of productive tillers. The geographical distribution of OsGATA8-H and its frequency change in historical accessions suggest its adaption to the fertile soil. Overall, this study provides molecular and evolutionary insights into the regulation of NUE and facilitates the breeding of rice cultivars with higher NUE.

OsCIPK2 mediated rice root microorganisms and metabolites to improve plant nitrogen uptake

Crop roots are colonized by large numbers of microorganisms, collectively known as the root-microbiome, which modulate plant growth, development and contribute to elemental nutrient uptake. In conditions of nitrogen limitation, the over-expressed Calcineurin B-like interacting protein kinase 2 (OsCIPK2) gene with root-specific promoter (RC) has been shown to enhance growth and nitrogen uptake in rice. Analysis of root-associated bacteria through high-throughput sequencing revealed that OsCIPK2 has a significant impact on the diversity of the root microbial community under low nitrogen stress. The quantification of nifH gene expression demonstrated a significant enhancement in nitrogen-fixing capabilities in the roots of RC transgenetic rice. Synthetic microbial communities (SynCom) consisting of six nitrogen-fixing bacterial strains were observed to be enriched in the roots of RC, leading to a substantial improvement in rice growth and nitrogen uptake in nitrogen-deficient soils. Forty and twenty-three metabolites exhibiting differential abundance were identified in the roots and rhizosphere soils of RC transgenic rice compared to wild-type (WT) rice. These findings suggest that OSCIPK2 plays a role in restructuring the microbial community in the roots through the regulation of metabolite synthesis and secretion. Further experiments involving the exogenous addition of citric acid revealed that an optimal concentration of this compound facilitated the growth of nitrogen-fixing bacteria and substantially augmented their population in the soil, highlighting the importance of citric acid in promoting nitrogen fixation under conditions of low nitrogen availability. These findings suggest that OsCIPK2 plays a role in enhancing nitrogen uptake by rice plants from the soil by influencing the assembly of root microbial communities, thereby offering valuable insights for enhancing nitrogen utilization in rice cultivation.

Physiological and Transcriptional Characteristics of Banana Seedlings in Response to Nitrogen Deficiency Stress

Nitrogen is a crucial element for the growth and development of plants, directly affecting crop growth and yield. To investigate the physiological and molecular mechanism of nitrogen-deficiency stress, we conducted an investigation into the effects of different nitrogen levels on the growth, photosynthetic characteristics, and gene transcription levels of banana seedlings. Compared with the control group with normal nitrogen levels (NN), the height of plants receiving Reduced-N (NR), Low-N (LN), and N-Free (NF) treatments was decreased by 0.45 cm, 2.5 cm, and 3.25 cm, respectively. Their dry weight was reduced by 1.63 g, 2.99 g, and 2.88 g, respectively. Conversely, the dry weight of the underground plant part in the LN and NF treatment groups exhibited an increase of 0.13 g and 0.16 g, respectively. Regarding photosynthetic characteristics, the Specialty Products Agricultural Division (SPAD) values of the NR, LN, and NF treatments showed reductions of 15.5%, 30.4%, and 35.9%, respectively, compared with those of the control treatments. The values of maximum photosynthetic efficiency (Fv/Fm), actual photosynthetic efficiency (Y(Ⅱ)), and relative electron transfer (ETR) of the banana seedlings decreased to different degrees after NR, LN, and NF treatment, and their values were positively correlated with N levels. Gene transcription analysis showed that N transport-related proteins, including NRT1.7, NRT2.3a, NRT2.3b, and NRT2.5, were significantly up-regulated to increase the nitrogen absorption capacity of plant roots. On the other hand, various transcription factors including GRAS, MYB, and WRKY were notably up-regulated, facilitating root growth and the expanding root absorption area, thereby enhancing nitrogen uptake. Furthermore, genes associated with endogenous hormone metabolic pathways such as gibberellin (GA), strigolactone (SL), and brassinosteroids (BR) were activated in banana plants subjected to low nitrogen stress, enhancing the plant’s ability to adapt to nitrogen-deficient conditions. These findings offer valuable insights into understanding the transcriptional regulatory mechanisms governing banana responses to low nitrogen stress and breeding new varieties with improved nutrient utilization.

Drive soil nitrogen transformation and improve crop nitrogen absorption and utilization - a review of green manure applications.

Green manure application presents a valuable strategy for enhancing soil fertility and promoting ecological sustainability. By leveraging green manures for effective nitrogen management in agricultural fields can significantly reduce the dependency of primary crops on chemical nitrogen fertilizers, thereby fostering resource efficiency. This review examines the current advancements in the green manure industry, focusing on the modulation of nitrogen transformation in soil and how crops absorb and utilize nitrogen after green manure application. Initially, the influence of green manure on soil nitrogen transformation is delineated, covering processes such as soil nitrogen immobilization, and mineralization, and losses including NH3, N2O, and NO3 --N leaching. The review then delves into the effects of green manure on the composition and function of soil microbial communities, highlighting their role in nitrogen transformation. It emphasizes the available nitrogen content in the soil, this article discussing nitrogen uptake and utilization by plants, including aspects such as nitrogen translocation, distribution, the root system, and the rhizosphere environment of primary crops. This provides insights into the mechanisms that enhance nitrogen uptake and utilization when green manures are reintroduced into fields. Finally, the review anticipates future research directions in modulating soil nitrogen dynamics and crop nitrogen uptake through green manure application, aiming to advance research and the development of the green manure sector.

Nutrients Uptake and Fruit Yield of Tomato (Lycopersicon Esculentum Mill.) Produced Using Home Sorted and Municipal Organic Materials as Nutrient Sources.

Tomato (Lycopersicon esculentum Mill.) is one of the most popular crops with a unique role in human diets especially in Nigeria. Nutritional quality of fruit is a reflection of uptake by the plant. The study investigated the uptake of Nitrogen, Phosphorus, Potassium, Calcium and Magnesium uptake by tomato with incorporation of home and municipal sorted solid waste. Screenhouse experiment was carried out at the College of Plant Science and Crop Production, while field experiment was conducted at the Directorate of University Farms, Federal University of Agriculture (Latitudes 7°13ʹN and 7°20ʹN and Longitudes 3°20ʹE and 3°28ʹE) during the early and late seasons of 2019. Roma VF and Ibadan-local varieties as test crop. The screenhouse experiment was factorial in Completely Randomized Design. The treatments were: composted municipal solid waste; composted home sorted waste; pyrolyzed municipal solid waste and pyrolyzed home sorted waste at the rate of 0, 5, 10 and 20 tha-1 each. The field experiment was set up in a randomized complete block design with incorporation of waste treatments at 10 t ha-1, all in three replicates. The treatments mentioned above for screenhouse were also used for field experiment. Data collected were subjected to Analysis of Variance and the means were separated using Duncan’s Multiple Range Test (p<0.05). The study was carried out in the wet and dry seasons. Nutrients (N, P, K, Ca and Mg) uptakes by plants were determined after laboratory analysis using nutrient concentration x dry matter (kg ha-1). Treatments had significant effects on the fruit yield of tomato. Composted home sorted waste at 5 t ha-1 resulted in highest uptake of nitrogen (5.32 mg kg-1), phosphorus (2.87 mg kg-1), potassium (26.10 mg kg-1) and magnesium (9.74 mg kg-1) in screenhouse compared with control and other treatments. Pyrolyzed wastes enhanced the fruit yield and nutrient uptake by plant relative to composted wastes in both seasons on the field. Pyrolyzed home sorted waste (PHSW) enhanced nitrogen uptake at early (186 kg ha-1) and late (108 kg ha-1) seasons. Pyrolyzed wastes (PHSW and PMSW) increased phosphorus uptake of 573 kg ha-1 and 507 kg ha-1 respectively in the early season while the highest phosphorus uptake of 339.6 kg ha-1 was observed with PHSW in the late season. Pyrolyzed municipal solid waste (PMSW) increased potassium uptake in both early (22.21 kg ha-1) and late (12.55 kg ha-1) seasons compared to control and other treatments applied. It was concluded that composted and pyrolyzed home sorted wastes improved the fruit yield and nutrient uptake in organic tomato production, and thus recommended for optimal production of tomato.

Enhancing Phosphorus and Nitrogen Uptake in Maize Crops with Food Industry Biosolids and Azotobacter nigricans.

The problem of phosphorus and nitrogen deficiency in agricultural soils has been solved by adding chemical fertilizers. However, their excessive use and their accumulation have only contributed to environmental contamination. Given the high content of nutrients in biosolids collected from a food industry waste treatment plant, their use as fertilizers was investigated in Zea mays plants grown in sandy loam soil collected from a semi-desert area. These biosolids contained insoluble phosphorus sources; therefore, given the ability of Azotobacter nigricans to solubilize phosphates, this strain was incorporated into the study. In vitro, the suitable conditions for the growth of Z. mays plants were determined by using biosolids as a fertilizer and A. nigricans as a plant-growth-promoting microorganism; in vitro, the ability of A. nigricans to solubilize phosphates, fix nitrogen, and produce indole acetic acid, a phytohormone that promotes root formation, was also evaluated. At the greenhouse stage, the Z. mays plants fertilized with biosolids at concentrations of 15 and 20% (v/w) and inoculated with A. nigricans favored the development of bending strength plants, which was observed on the increased stem diameter (>13.5% compared with the negative control and >7.4% compared with the positive control), as well as a better absorption of phosphorus and nitrogen, the concentration of which increased up to 62.8% when compared with that in the control treatments. The interactions between plants and A. nigricans were observed via scanning electron microscopy. The application of biosolids and A. nigricans in Z. mays plants grown in greenhouses presented better development than when Z. mays plants were treated with a chemical fertilizer. The enhanced plant growth was attributed to the increase in root surface area.

Comparative genomics reveals a unique nitrogen-carbon balance system in Asteraceae

The Asteraceae (daisy family) is one of the largest families of plants. The genetic basis for its high biodiversity and excellent adaptability has not been elucidated. Here, we compare the genomes of 29 terrestrial plant species, including two de novo chromosome-scale genome assemblies for stem lettuce, a member of Asteraceae, and Scaevola taccada, a member of Goodeniaceae that is one of the closest outgroups of Asteraceae. We show that Asteraceae originated ~80 million years ago and experienced repeated paleopolyploidization. PII, the universal regulator of nitrogen-carbon (N-C) assimilation present in almost all domains of life, has conspicuously lost across Asteraceae. Meanwhile, Asteraceae has stepwise upgraded the N-C balance system via paleopolyploidization and tandem duplications of key metabolic genes, resulting in enhanced nitrogen uptake and fatty acid biosynthesis. In addition to suggesting a molecular basis for their ecological success, the unique N-C balance system reported for Asteraceae offers a potential crop improvement strategy.

Response of Sorghum [Sorghum bicolor(L.) Moench] to Phosphorus and Nitrogen Fertilization under Rainfed Conditions, Blue Nile State – Sudan*

Two field experiments were conducted on a Typicchromusterts, fine, smectitic, isohyperthermic soil series in the DamazinResearch Station farm during two seasons (2005/06 and 2006/07). Theobjective was to investigate the effect of phosphorus (P) and nitrogen (N)and their interactions on sorghum [Sorghum bicolor (L.) Moench] growthand grain yield. A randomized complete block design with four replicateswas used to execute the experiments. Plant height, grain yield and drymatter were significantly increased by N and P applications, in bothseasons.The average yield of sorghum grain in the two seasons was 0.6tons ha-1 for the control and 4.4 tons ha-1 for the highest fertilizer treatment(P 80 N80 ). There were mutually synergistic effects between N and P whichsignificantly (P<0.0001) promoted growth and yield of sorghum.Phosphorus enhanced nitrogen uptake and nitrogen use efficiency and viceversa. At all N applications, phosphorus use efficiency tended to decreasewith increase in the rate of P application. The highly significant responseof sorghum to P and N fertilizers warrant recommending their applicationunder the rainfed conditions of Damazin, Sudan.

Nodulation alleviates the stress of lower water availability in Vachellia sieberiana

The genus Vachellia (Fabaceae) has a pan-tropical distribution and numerous Vachellia species are currently observed to be expanding their indigenous ranges and/or are invasive. Most Vachellia species have the capacity to enhance nitrogen uptake via an N2-fixing rhizobial mutualism that manifests in specialized root nodule structures enabling the catalysis of atmospheric N2 into a plant useable form. Improved understanding of nodulation may provide new insight to the changing patterns of ecological success of Vachellia species. Here, we investigated how the seedling growth, allometry and nodulation of two common Vachellia species, the arid Vachellia erioloba and the mesic Vachellia sieberiana, responded to varied levels of water availability. Seedlings were grown at 4%, 8% and 16% soil moisture content (SMC) for four months. The seedling growth and allometry of V. erioloba was unresponsive to changing water availability, and no nodulation was observed. The allometry of V. sieberiana was responsive to changing water availability and nodulation was observed; with the highest nodule biomass and growth rate recorded at 4% SMC. These patterns suggest that V. erioloba does not require the rhizobial mutualism, possibly due to lower competitive interactions between woody plants and grass in the arid savanna. Whereas, due to the competitive vegetation interactions typical in the mesic savanna, N2- fixation via nodule development could provide V. sieberiana a competitive advantage over grass not only in limited N conditions, but also during periods of lower water availability.

Low Nitrogen Stress Promotes Root Nitrogen Uptake and Assimilation in Strawberry: Contribution of Hormone Networks

Low nitrogen stress severely impedes crop growth and productivity. There has been substantial research on root adaptation to low nitrogen conditions in many plant species. However, the mechanism underlying the morphological response of the strawberry (Fragaria × ananassa Duch.) root to low-NO3− or low-NH4+ stress remains poorly understood. Strawberry plants were hydroponically cultivated under 1 mM NO3−, 1 mM NH4+, and control (15 mM NO3−) conditions to assess the physiological responses of their roots to low nitrogen stress. As a result, low nitrogen stresses increased the fresh weight of root, lateral root density, and root surface area, as well as enhanced the accumulation of indole-3-acetic acid and jasmonic acid while significantly reducing salicylic acid in the roots. Correspondingly, low nitrogen stresses increased PM H+-ATPase activity. Low-NO3− stress enhanced the activities of nitrate reductase and glutamine synthetase, whereas low-NH4+ treatment led to higher glutamine synthetase and glutamate synthase activities. Collectively, the present results demonstrate that low nitrogen stresses enhance nitrogen uptake of strawberry roots by regulating hormones (indole-3-acetic acid, jasmonic acid, and salicylic acid) and thereby mediating PM H+-ATPase activity, while promoting nitrogen metabolism by upregulating the activities of nitrate reductase, glutamine synthetase, and glutamate synthase. In conclusion, low nitrogen conditions may facilitate more efficient acquisition of available N from the soil by strawberry root system.

Role of Melatonin and Nitrogen Metabolism in Plants: Implications under Nitrogen-Excess or Nitrogen-Low

Melatonin is a new plant hormone involved in multiple physiological functions in plants such as germination, photosynthesis, plant growth, flowering, fruiting, and senescence, among others. Its protective role in different stress situations, both biotic and abiotic, has been widely demonstrated. Melatonin regulates several routes in primary and secondary plant metabolism through the up/down-regulation of many enzyme/factor genes. Many of the steps of nitrogen metabolism in plants are also regulated by melatonin and are presented in this review. In addition, the ability of melatonin to enhance nitrogen uptake under nitrogen-excess or nitrogen-low conditions is analyzed. A model that summarizes the distribution of nitrogen compounds, and the osmoregulation and redox network responses mediated by melatonin, are presented. The possibilities of using melatonin in crops for more efficient uptake, the assimilation and metabolization of nitrogen from soil, and the implications for Nitrogen Use Efficiency strategies to improve crop yield are also discussed.

Advanced treatment of food processing effluent by indigenous microalgae-bacteria consortia: Population dynamics and enhanced nitrogen uptake

The potential of indigenous microalgae-bacteria consortia (IMBC) to recover nutrients from food processing effluents (FPE) supports the basis for advanced effluent polishing and value-added biomass generation. In this study, the effluent polishing potential of an FPE-borne IMBC treating FPE and synthetic wastewater (SWW) was investigated regarding nutrient, coliform bacteria, and chemical oxygen demand (COD) removal as well as the IMBC species evolution, and pigment production. Species evolution and diversity of the IMBC in FPE and SWW were influenced by nitrogen levels (3.83 mg/L and 32.61 mg/L NH4+, respectively). More blue-green microalgae were observed in SWW (0.96 mg/L phycocyanin) whilst diatoms dominated in FPE (0.05 mg/L phycocyanin). Total coliform bacteria removal influenced COD reduction and this had a significant effect on dissolved oxygen production. The study offers new insights into the feasibility of using IMBC biofilm for advanced FPE polishing and nutrient recovery (0.98 mg/L NH4+, 0.85 mg/L PO43−, 0.84 mg/L COD, 3.2 g/L protein, and 2.8 g/L carbohydrates), demonstrating that it is possible to use IMBC biofilm for post-treatment of FPE, removing the residual N and P to prevent eutrophication.

Biological nitrification inhibitor-trait enhances nitrogen uptake by suppressing nitrifier activity and improves ammonium assimilation in two elite wheat varieties.

Synthetic nitrification inhibitors (SNI) and biological nitrification inhibitors (BNI) are promising tools to limit nitrogen (N) pollution derived from agriculture. Modern wheat cultivars lack sufficient capacity to exude BNIs, but, fortunately, the chromosome region (Lr#n-SA) controlling BNI production in Leymus racemosus, a wild relative of wheat, was introduced into two elite wheat cultivars, ROELFS and MUNAL. Using BNI-isogenic-lines could become a cost-effective, farmer-friendly, and globally scalable technology that incentivizes more sustainable and environmentally friendly agronomic practices. We studied how BNI-trait improves N-uptake, and N-use, both with ammonium and nitrate fertilization, analysing representative indicators of soil nitrification inhibition, and plant metabolism. Synthesizing BNI molecules did not mean a metabolic cost since Control and BNI-isogenic-lines from ROELFS and MUNAL presented similar agronomic performance and plant development. In the soil, ROELFS-BNI and MUNAL-BNI plants decreased ammonia-oxidizing bacteria (AOB) abundance by 60% and 45% respectively, delaying ammonium oxidation without reducing the total abundance of bacteria or archaea. Interestingly, BNI-trait presented a synergistic effect with SNIs since made it also possible to decrease the AOA abundance. ROELFS-BNI and MUNAL-BNI plants showed a reduced leaf nitrate reductase (NR) activity as a consequence of lower soil formation and a higher amino acid content compared to BNI-trait lacking lines, indicating that the transfer of Lr#-SA was able to induce a higher capacity to assimilate ammonium. Moreover, the impact of the BNI-trait in wheat cultivars was also noticeable for nitrate fertilization, with improved N absorption, and therefore, reducing soil nitrate content.

Nitrification upon Nitrogen Starvation and Recovery: Effect of Stress Period, Substrate Concentration and pH on Ammonia Oxidizers’ Performance

Nitrification has been widely applied in wastewater treatment, however gaining more insight into the nitrifiers’ physiology and stress response is necessary for the optimization of nutrient removal and design of advanced processes. Since nitrification initiates with ammonia oxidation performed by ammonia-oxidizing bacteria (AOB), the purpose of this study was to investigate the effects of short-term ammonia starvation on nitrogen uptake and transformation efficiency, as well as the performance of starved nitrifiers under various initial substrate concentrations and pH values. Ammonium deprivation for 3 days resulted in fast ammonium/ammonia accumulation upon nitrogen availability, with a maximum uptake rate of 3.87 mmol gprotein−1 min−1. Furthermore, a delay in the production of nitrate was observed with increasing starvation periods, resulting in slower recovery and lower nitrification rate compared to non-starved cells. The maximum accumulation capacity observed was 8.51% (w/w) independently of the external nitrogen concentration, at a range of 250–750 mg N L−1, while pH significantly affected ammonia oxidizers’ response, with alkaline values enhancing nitrogen uptake. In total, ammonia accumulation after short-term starvation might serve as an important strategy that helps AOB restore their activity, while concurrently it could be applied in wastewater treatment for effective nitrogen removal and subsequent biomass utilization.

Nitric oxide generated by Piriformospora indica-induced nitrate reductase promotes tobacco growth by regulating root architecture and ammonium and nitrate transporter gene expression

ABSTRACT Nitric oxide (NO) is involved not only in the regulation of plant growth, development, and stress responses but also in the regulation of plant-microbe interactions. Here, we demonstrate that Piriformospora indica can induce tobacco nitrate reductase to produce a NO signal in roots which enhances nitrogen uptake capacity by inducing the expression of ammonium and nitrate transporter genes and the development of lateral root and root hair, thereby promoting tobacco growth. In addition, the NO signal induced by P. indica is significantly different from that induced by the pathogen Phytophthora nicotianae. Inoculation with P. indica did not produce H2O2 and maintained high expression of Phytoglobin 1 in roots, resulting in a significantly lower NO level than in the roots inoculated with P. nicotianae. These findings suggest that an appropriate NO level is the likely basis of plant-P. indica symbiosis, which promotes the growth of host plants.