OsNPF3.1,a nitrate,abscisic acid and gibberellin transporter gene,is essential for rice tillering and nitrogen utilization efficiency

Low-affinity nitrate transporter genes have been identified in subfamilies 4-8 of the rice nitrate transporter 1(NRT1)/peptide transporter family(NPF),but the OsNPF3 subfamily responsible for nitrate and phytohormone transport and rice growth and development remains unknown.In this study,we described OsNPF3.1 as an essential nitrate and phytohormone transporter gene for rice tillering and nitrogen utilization efficiency(NUtE).OsNPF3.1 possesses four major haplotypes of its promoter sequence in 517 cultivars,and its expression is positively associated with tiller number.Its expression was higher in the basal part,culm,and leaf blade than in other parts of the plant,and was strongly induced by nitrate,abscisic acid(ABA)and gibberellin 3(GA_3)in the root and shoot of rice.Electrophysiological experiments demonstrated that OsNPF3.1 is a pH-dependent low-affinity nitrate transporter,with rice protoplast uptake assays showing it to be an ABA and GA_3 transporter.OsNPF3.1 overexpression significantly promoted ABA accumulation in the roots and GA accumulation in the basal part of the plant which inhibited axillary bud outgrowth and rice tillering,especially at high nitrate concentrations.The NUtE of OsNPF3.1-overexpressing plants was enhanced under low and medium nitrate concentrations,whereas the NUtE of OsNPF3.1 clustered regularly interspaced short palindromic repeats(CRISPR)plants was increased under high nitrate concentrations.The results indicate that OsNPF3.1 transports nitrate and phytohormones in different rice tissues under different nitrate concentrations.The altered OsNPF3.1 expression improves NUtE in the OsNPF3.1-overexpressing and CRISPR lines at low and high nitrate concentrations,respectively.

Variation of Nitrogen Uptake and Utilization Efficiency of Mid-Season Hybrid Rice at Different Ecological Sites under Different Nitrogen Application Levels

[Objective] The study aimed at investigating the effects of different geographic sites,soil chemical characteristics and nitrogen application levels on nitrogen accumulation and distribution in different organs and utilization efficiency for mid-season hybrid rice.[Method] By using mid-season rice varieties II-you 7 and Yuxiangyou203 as the experimental materials,field experiment was conducted at seven ecological sites in four provinces or cities in Southwestern China in 2009.A total of four nitrogen application levels were set as follows：by using 75 kg/hm2 of P2O5 and 75 kg/hm2 of K2O as the base fertilizer,extra 0,90,150 and 210 kg/hm2 of nitrogen fertilizer（in which,base fertilizer,base-tillering fertilizer and base-earing fertilizer respectively accounted for 60%,20% and 20%.） was applied,respectively.In the split-plot design,fertilizer was considered as the main factor while rice variety was taken as the secondary factor.A total of eight treatments were set with three replications.[Result] Highly significant differences of grain yield were found among seven locations,two varieties,four nitrogen application levels,interactions of site × variety and site × nitrogen application level,but the interaction of variety ×nitrogen application level had no significant influence on rice yield.There were highly significant effects of site,varieties and nitrogen application level on dry matter production,nitrogen content,nitrogen utilization efficiency.Highly significant negative correlations between uptake efficiency and utilization efficiency for nitrogen were found;and multiple stepwise regression analysis showed that nitrogen uptake-utilization efficiency were significantly influenced by different ecological sites,chemical quality of soil and the levels of nitrogen application.[Conclusion] The research will provide theoretical and practical basis for the highly efficient application of nitrogen in mid-season hybrid rice cultivation.

Methods on Identification and Screening of Rice Genotypes with High Nitrogen Efficiency

In order to establish methods for indentification and screening of rice genotypes with high nitrogen （N） efficiency, N absorption efficiency （NAE）, N utilization efficiency （NUE） and N harvest index （NHI） in ten rice genotypes were investgated at the elongation, booting, heading and maturity stages under six N levels in a pot experiment with soil-sand mixtures at various ratios. NAE in various rice genotypes firstly increased, peaked under a medium nitrogen rate of 0.177 g/kg and then decreased, but NUE and NHI always decreased with increasing nitrogen levels. NAE in various rice genotypes ever increased with growing process and NUE indicated a descending tendency of elongation stage〉heading stage〉maturity stage〉booting stage. N level influenced rice NAE, NUE and NHI most, followed by genotype, and the both effects were significant at 0.01 level. In addition, the interaction effects of genotype and nitrogen level on rice NAE and NUE were significant at 0.01 level, but not significant on rice NHI. Because the maximum differences of NAE and NUE were found at the elongation stage, it was thought to be the most suitable stage for identification and screening these two paremeters. Therefore, the optimum conditions for identification and screening of rice NAE, NUE and NHI in a pot experiment were the nitrogen rate of 0.157 g/kg at the elongation stage, low nitrogen at the elongation stage, and the nitrogen rate of 0.277 g/kg at the maturity stage, respectively.

Integrated management strategy for improving the grain yield and nitrogen-use efficiency of winter wheat

Understanding of how combinations of agronomic options can be used to improve the grain yield and nitrogen use efficiency（NUE） of winter wheat is limited. A three-year experiment involving four integrated management strategies was conducted from 2013 to 2015 in Tai＇an, Shandong Province, China, to evaluate changes in grain yield and NUE. The integrated management treatments were as follows： current practice（T1）; improvement of current practice（T2）; high-yield management（T3）, which aimed to maximize grain yield regardless of the cost of resource inputs; and integrated soil and crop system management（T4） with a higher seeding rate, delayed sowing date, and optimized nutrient management. Seeding rates increased by 75 seeds m^-2 with each treatment from T1（225 seeds m^-2） to T4（450 seeds m^-2）. The sowing dates were delayed from T1（5 th Oct.） to T2 and T3（8 th Oct.）, and to T4 treatment（12 th Oct.）. T1, T2, T3, and T4 received 315, 210, 315, and 240 kg N ha^-1, 120, 90, 210 and 120 kg P2O5 ha^-1, 30, 75, 90, and 45 kg K2O ha^-1, respectively. The ratio of basal application to topdressing for T1, T2, T3, and T4 was 6：4, 5：5, 4：6, and 4：6, respectively, with the N topdressing applied at regreening for T1 and at jointing stage for T2, T3, and T4. The P fertilizers in all treatments were applied as basal fertilizer. The K fertilizer for T1 and T2 was applied as basal fertilizer while the ratio of basal application to topdressing（at jointing stage） of K fertilizer for both T3 and T4 was 6：4. T1, T2, T3, and T4 were irrigated five, four, four and three times, respectively. Treatment T3 produced the highest grain yield among all treatments over three years and the average yield was 9 277.96 kg ha^-1. Grain yield averaged across three years with the T4 treatment（8 892.93 kg ha^-1） was 95.85% of that with T3 and was 21.72 and 6.10% higher than that with T1（7 305.95 kg ha^-1） and T2（8 381.41 kg ha^-1）, respectively. Treatment T2 produced the highest NUE of all the integrated treatments. The NUE with T4 was 95.36% of that with T2 and was 51.91 and 25.62% higher than that with T1 and T3, respectively. The N uptake efficiency（UPE） averaged across three years with T4 was 50.75 and 16.62% higher than that with T1and T3, respectively. The N utilization efficiency（UTE） averaged across three years with T4 was 7.74% higher than that with T3. The increased UPE with T4 compared with T3 could be attributed mostly to the lower available N in T4, while the increased UTE with T4 was mainly due to the highest N harvest index and low grain N concentration, which consequently led to improved NUE. The net profit for T4 was the highest among four treatments and was 174.94, 22.27, and 28.10% higher than that for T1, T2, and T3, respectively. Therefore, the T4 treatment should be a recommendable management strategy to obtain high grain yield, high NUE, and high economic benefits in the target region, although further improvements of NUE are required.

Effects of Increased Planting Density with ReducedNitrogen Application on Yield Formation and NitrogenUtilization of Autumn Maize

With the change of cropping system in the middle reaches of the Yangtze River,the planting area of autumn maize is gradually increasing.However,the cultivation techniques are still under improvement for higher yield and nitrogen efficiency of autumn maize.Increase in planting density with reduced nitrogen fertilizer application is one of the important paths to achieve high yield and high nitrogen utilization efficiency.Meanwhile,the effect needs to be verified for autumn maize.The semi-compact autumn maize variety Qinyu 58 was planted under different planting densities and nitrogen fertilizer amounts with the split plot design.Different nitrogen application rates were arranged in the main plots,including the conventional nitrogen application(N300,300 kg/hm^2),30%reduction from the conventional treatment(N210,210 kg/hm^2)and no nitrogen application(N0).Different planting densities were arranged in the sub-split plots,including the conventional planting density(D60,60000 plants/hm2),medium density(D78,78000 plants/hm^2)and high density(D93,93000 plants/hm2).The effects of nitrogen fertilizer,planting density and their interaction effects on canopy structure,dry matter accumulation,yield and nitrogen use efficiency of autumn maize were studied.The nitrogen application rate and planting density had obvious interaction effects on the yield formation of autumn maize.Compared with the conventional cultivation(N300D60),increasing the planting density with 30%reduction in nitrogen application(N210)can obviously increase the canopy light interception rate,LAI,dry matter accumulation and yield.However,there was no significant change in canopy light interception rate,LAI,dry matter accumulation,grain weight and yield between D93 and D78.Compared with N300D60,nitrogen translocation efficiency and nitrogen contribution proportion to grain nitrogen did not change significantly in autumn maize grown under N210 and D78 treatments,whereas nitrogen partial productivity,nitrogen agronomic efficiency and recovery and utilization efficiency of nitrogen fertilizer increased significantly.Moreover,high density(D93)planting at N210 plots significantly improved nitrogen transport efficiency and utilization efficiency in autumn maize.Therefore,the suitable planting density of the autumn maize variety Qinyu 58 in Hubei Province is recommended a value of 78000 plants/hm^2,with the nitrogen application rate of 210 kg/hm2,which can achieve the target of higher yield by increasing density and reducing nitrogen.

Effects of Nitrogen on N Uptake,Grain Yield and Quality of Medium-Gluten Wheat Yangmai 10

The effects of the basal and top-dressing nitrogen (N) on N uptake and translocation, N utilization efficiency, grain yieldand quality of medium-gluten winter wheat Yangmai 10 were studied from 2000 to 2002. The main results were as follows.Nitrogen content and nitrogen accumulation in plant at maturity increased with the amount of N application. Grain proteincontent and wet gluten content were significantly correlated with applied N. There was a significantly positive correlationbetween nitrogen accumulation before anthesis (NBA) and basal N fertilizer, and between nitrogen accumulation afteranthesis (NAA) and top-dressing N. N accumulated in grains was significantly correlated to NBA, NAA and N translocationfrom vegetative organs after anthesis (NTVA). NBA was significantly correlated with N application, but NAA and NTVAhad a quadratic curve correlation with applied N. N fertilizer use efficiency (NUE) had a quadratic curve correlation withapplied N, and the NUE was high when basal and top-dressing N was equally applied. For the medium-gluten wheatYangmai 10 under the same N application ratio, there was a N-regulating effect when the N application was less than266.55 kg ha-1, a stagnation of yield and quality when N application ranged from 266.55 to 309.08 kg ha-1, and an excessiveN application when the N application rate was greater than 309.08 kg ha-1. Under the conditions of this experiment, theprecise N application is 220-270 kg ha-1 with basal and top-dressing N equally used when a grain yield of more than 6 750kg ha-1, protein content higher than 12%, wet gluten content more than 30% and NUE greater than 40% could be obtained.

Effect of Nitrogen Applied Before Transplanting on NUE in Rice

Nitrogen （N） application before transplanting, where N fertilizers are applied in seedling-bed and carried to the paddy field with seedlings, is a novel method proposed in this article aiming for improving nitrogen utilization efficiency （NUE） in rice. The effect of this method on mineral N distribution in the rhizosphere soil was investigated in a field experiment with a japonica variety, Ningjing 2, in seasons of 2004 and 2005. There were four levels of N applied 16 h before transplanting： zero N （NO）, 207 kg ha^-1 （NL）, 310.5 kg ha^-1 （NM）, and 414 kg ha^-1 （NH）. The result indicated that N fertilizer before transplantation had positive effect of increasing mineral N content in the rhizosphere soil of rice. Generally, N content in the rhizosphere soil of rice tended to increase with the amount of N fertilizer before transplanting, with the NH treatment having the largest effect. Additionally, N fertilizer before transplanting had significant influence on rice NUE and grain yield. Compared with other treatments, the NM treatment showed the largest influence, with basal-tillering NUE, total NUE, and grain yield being 15%, 12%, and 529.5 kg ha^-1 higher than those of NO treatment. This result indicated that N fertilizer before transplantation had positive effect on mineral N distribution in the rhizosphere soil of rice, thus improving NUE and grain yield.

Dietary crude protein and protein solubility manipulation enhances intestinal nitrogen absorption and mitigates reactive nitrogen emissions through gut microbiota and metabolome reprogramming in sheep

Dietary nutrient manipulation(e.g.protein fractions)could lower the environmental footprints of ruminants,especially reactive nitrogen(N).This study investigated the impacts of dietary soluble protein(SP)levels with decreased crude protein(CP)on intestinal N absorption,hindgut N metabolism,fecal microbiota and metabolites,and their linkage with N metabolism phenotype.Thirty-two male Hu sheep,with an age of six months and an initial BW of 40.37±1.18 kg,were randomly assigned to four dietary groups.The control diet(CON),aligning with NRC standards,maintained a CP content of 16.7%on a dry matter basis.Conversely,the experimental diets(LPA,LPB,and LPC)featured a 10%reduction in CP compared with CON,accompanied by SP adjustments to 21.2%,25.9%,and 29.4%of CP,respectively.Our results showed that low-protein diets led to significant reductions in the concentrations of plasma creatinine,ammonia,urea N,and fecal total short-chain fatty acids(SCFA)(P<0.05).Notably,LPB and LPC exhibited increased total SCFA and propionate concentrations compared with LPA(P<0.05).The enrichment of the Prevotella genus in fecal microbiota associated with energy metabolism and amino acid(AA)biosynthesis pathways was evident with SP levels in low-protein diets of approximately 25%to 30%.Moreover,LPB and LPC diets demonstrated a decrease in fecal NHþ4 eN and NO2 eN contents as well as urease activity,compared with CON(P<0.05).Concomitantly,reductions in fecal glutamic acid dehydrogenase gene(gdh),nitrite reductase gene(nirS),and nitric oxide reductase gene(norB)abundances were observed(P<0.05),pointing towards a potential reduction in reactive N production at the source.Of significance,the up-regulation of mRNA abundance of AA and peptide transporters in the small intestine(duodenum,jejunum,and ileum)and the elevated concentration of plasma AA(e.g.arginine,methionine,aspartate,glutamate,etc.)underscored the enhancement of N absorption and N efficiency.In summary,a 10%reduction in CP,coupled with an SP level of approximately 25%to 30%,demonstrated the potential to curtail reactive N emissions through fecal Prevotella enrichment and improve intestinal energy and N utilization efficiency.

Function, transport, and regulation of amino acids: What is missing in rice?

Amino acids are essential plant compounds serving as the building blocks of proteins,the predominant forms of nitrogen(N)distribution,and signaling molecules.Plant amino acids derive from root acquisition,nitrate reduction,and ammonium assimilation.Many amino acid transporters(AATs)mediating transfer processes of amino acids have been functionally characterized in Arabidopsis,whereas the function and regulation of the vast majority of AATs in rice(Oryza sativa L.)and other crops remain unknown.In this review,we summarize the current understanding of amino acids in the rhizosphere and in metabolism.We describe their function as signal molecules and in regulating plant architecture,flowering time,and defense against abiotic stress and pathogen attack.AATs not only function in root acquisition and translocation of amino acids from source to sink organs,regulating N uptake and use efficiency,but also as transporters of non-amino acid substrates or as amino acid sensors.Several AAT genes show natural variations in their promoter and coding regions that are associated with altered uptake rate of amino acids,grain N content,and tiller number.Development of an amino acid transfer model in plants will advance the manipulation of AATs for improving rice architecture,grain yield and quality,and N-use efficiency.

Experimental study on water-saving and emission-reduction effects of controlled drainage technology

Field experiments and laboratory analysis were carried out to determine the effects of controlled drainage（CTD） and conventional drainage（CVD） technologies on drainage volume, concentrations of NH4^＋ -N, NO3^-N, and total phosphorus（TP）, nitrogen and phosphorus losses, rice yield,and water utilization efficiency. Results show that CTD technology can effectively reduce drainage times and volume; NH4^＋ -N, NO3^-N, and TP concentrations, from the first to the fourth day after four rainstorms decreased by 28.7%e46.7%, 37.5%e47.5%, and 22.7e31.2%, respectively,with CTD. These are significantly higher rates of decrease than those observed with CVD. CTD can significantly reduce nitrogen and phosphorus losses in field drainage, compared with CVD; the reduction rates observed in this study were, respectively, 66.72%, 55.56%, and 42.81% for NH4^＋ -N, NO3^-N, and TP. Furthermore, in the CTD mode, the rice yield was cut slightly. In the CVD mode, the water production efficiencies in unit irrigation water quantity, unit field water consumption, and unit evapotranspiration were, respectively, 0.85, 0.48, and 1.22 kg/m^3, while in the CTD mode they were 2.91, 0.84, and 1.61 kg/m^3 din other words, 3.42, 1.75, and 1.32 times those of CVD. Furthermore, the results of analysis of variance（ANOVA） show that the indicators in both the CVD and CTD modes, including the concentrations of NH4^＋ -N, NO3^-N, and TP, the losses of NH4^＋ -N, NO3^-N, and TP, irrigation water quantity, and water consumption, showed extremely significant differences between the modes, but the rice yield showed no significant difference.

Responses of photosynthetic characteristics and enzyme activity of nitrogen metabolism to low nitrogen in maize with different nitrogen tolerance

Understanding the physiological processes associated with leaf photosynthetic characteristics and nitrogen(N)assimilation during grain-filling stage are helpful for enhancing nitrogen utilization efficiency(NUtE)of maize.In this study,the leaf photosynthetic and N assimilation parameters in maize,including Zhengdan 958(ZD958),a low-N tolerance cultivar and Huanong 138(HN138),a low-N sensitive cultivar under different N rates were examined.Results showed that ZD958 displayed significant increases on grain yield and NUtE than that in HN138.Analyses on the leaf photosynthetic and N assimilation-associated processes indicated that ZD958 had higher leaf N remobilization(Rem N),net photosynthetic rate(Pn)and photosynthetic N use efficiency(PNUE)with respect to those of HN138 during grain-filling stage.In addition,ZD958 was also shown to be higher activities of leaf nitrate reductase(NR),glutamine synthetase(GS),nitrate reductase(GDH)and glutamine synthetase(GAGOT)than those of HN138.The leaf PNUE was significantly positively correlated with NR,GS,GDH,GOGAT suggesting that leaf PNUE and NR,GS,GDH,GOGAT jointly determined the N remobilization efficiency and the leaf N remobilization during post-silking.These results suggested that ZD958 possessed improved PNUE,NR and GS activities in leaves during grain-filling stage that contributes improve grain weights and yield formation capacities upon under low-N conditions.