Ammonium uptake in plant roots is mediated by AMT/MEP/Rh-type ammonium transporters. Out of five AMTs being expressed in Arabidopsis roots, four AMT1-type transporters contribute to ammonium uptake, whereas no physiol...Ammonium uptake in plant roots is mediated by AMT/MEP/Rh-type ammonium transporters. Out of five AMTs being expressed in Arabidopsis roots, four AMT1-type transporters contribute to ammonium uptake, whereas no physiological function has so far been assigned to the only homolog belonging to the MEP subfamily, AMT2;1. Based on the observation that under ammonium supply, the transcript levels of AMT2;1 increased and its promoter activity shifted preferentially to the pericycle, we assessed the contribution of AMT2;1 to xylem loading. When exposed to ^15N-labeled ammonium, amt2;1 mutant lines translocated less tracer to the shoots and contained less ammonium in the xylem sap. Moreover, in an amtl;1 amtl;2 amtl ;3 amt2;1 quadruple mutant （qko）, co-expression of AMT2;1 with either AMT1;2 or AMT1;3 significantly enhanced ^15N translocation to shoots, indicating a cooperative action between AMT2;1 and AMT1 transporters. Under N deficiency, proAMT2;1-GFP lines showed enhanced promoter activity predominantly in cortical root cells, which coincided with elevated ammonium influx conferred by AMT2;1 at millimolar sub- strate concentrations. Our results indicate that in addition to contributing moderately to root uptake in the low-affinity range, AMT2;1 functions mainly in root-to-shoot translocation of ammonium, depending on its Cell-type-specific expression in response to the plant nutritional status and to local ammonium gradients.展开更多
Supply of CdCl2 in the presence of NH4NO3 to excised etiolated maize leaf segments during greening decreased the glutamine synthetase and nicotinamide adenine dinucleotide reduced (NADH) dependent glutamate synthase a...Supply of CdCl2 in the presence of NH4NO3 to excised etiolated maize leaf segments during greening decreased the glutamine synthetase and nicotinamide adenine dinucleotide reduced (NADH) dependent glutamate synthase activities, while the ferredoxin (Fd) dependent glutamate synthase and glutamate dehydrogenase activities were increased. Inclusion of inorganic nitrogen, metabolites and the inhibitor influenced the effect of Cd on glutamine synthetase activity. The % inhibition of activity caused by Cd was higher with NO3<sup style='margin-left:-6px;'>- but lower with NH4<sup style='margin-left:-6px;'>+. Glutamine, 2-oxoglutarate, glutathione and sucrose decreased the % inhibition by Cd with the more prominent effect with glutamine and sucrose. Methionine sulfoximine exerted a more prominent effect for + Cd enzyme at lower concentration. The results indicate the involvement of reciprocal effects of Cd on glutamine synthetase and glutamate dehydrogenase activities and also on NADH- and Fd-glutamate synthase activities. For the inhibitory effect of Cd on glutamine synthetase activity, NH4<sup style='margin-left:-6px;'>+, glutamine, 2-oxoglutarate, glutathione and sucrose exerted a protective effect with the sucrose being most effective.展开更多
The biological treatment of wastewater with high concentrations of ammonia nitrogen has become a hot research issue,but there are limited reports on the mechanism of ammonia nitrogen utilization by microorganisms.In t...The biological treatment of wastewater with high concentrations of ammonia nitrogen has become a hot research issue,but there are limited reports on the mechanism of ammonia nitrogen utilization by microorganisms.In this paper,a transcriptomic approach was used to investigate the differences in gene expression at 500.0 mg/L(Amo 500)and 100.0 mg/L(Amo 100)ammonium concentrations to reveal the mechanism of ammonia nitrogen removal from water by Pseudomonas stutzeri F2.The transcriptome data showed 1015(459 up-regulated and 556 down-regulated)differentially expressed genes with functional gene annotation related to nitrogen source metabolism,glycolysis,tricarboxylic acid cycle,extracellular polysaccharide synthesis,energy conversion and transmembrane transport,revealing the metabolic process of ammonium nitrogen conversion to biological ni-trogen in P.stutzeri F2 through assimilation.To verify the effect of ammonium transporter protein(AmtB)of cell membrane on assimilation,a P.stutzeri F2-ΔamtB mutant strain was obtained by constructing a knockout plasmid(pK18mobsacB-ΔamtB),and it was found that the growth characteristics and ammonium removal rate of the mutant strain were significantly reduced at high ammonium concentration.The carbon source components and dissolved oxygen conditions were optimized after analyzing the transcriptome data,and the ammonium removal rate was increased from 41.23%to 94.92%with 500.0 mg/L ammonium concentration.The study of P.stutzeri F2 transcript level reveals the mechanism of ammonia nitrogen influence on microbial assimilation process and improvement strategy,which provides a new strategy for the treatment of ammonia nitrogen wastewater.展开更多
文摘Ammonium uptake in plant roots is mediated by AMT/MEP/Rh-type ammonium transporters. Out of five AMTs being expressed in Arabidopsis roots, four AMT1-type transporters contribute to ammonium uptake, whereas no physiological function has so far been assigned to the only homolog belonging to the MEP subfamily, AMT2;1. Based on the observation that under ammonium supply, the transcript levels of AMT2;1 increased and its promoter activity shifted preferentially to the pericycle, we assessed the contribution of AMT2;1 to xylem loading. When exposed to ^15N-labeled ammonium, amt2;1 mutant lines translocated less tracer to the shoots and contained less ammonium in the xylem sap. Moreover, in an amtl;1 amtl;2 amtl ;3 amt2;1 quadruple mutant （qko）, co-expression of AMT2;1 with either AMT1;2 or AMT1;3 significantly enhanced ^15N translocation to shoots, indicating a cooperative action between AMT2;1 and AMT1 transporters. Under N deficiency, proAMT2;1-GFP lines showed enhanced promoter activity predominantly in cortical root cells, which coincided with elevated ammonium influx conferred by AMT2;1 at millimolar sub- strate concentrations. Our results indicate that in addition to contributing moderately to root uptake in the low-affinity range, AMT2;1 functions mainly in root-to-shoot translocation of ammonium, depending on its Cell-type-specific expression in response to the plant nutritional status and to local ammonium gradients.
文摘Supply of CdCl2 in the presence of NH4NO3 to excised etiolated maize leaf segments during greening decreased the glutamine synthetase and nicotinamide adenine dinucleotide reduced (NADH) dependent glutamate synthase activities, while the ferredoxin (Fd) dependent glutamate synthase and glutamate dehydrogenase activities were increased. Inclusion of inorganic nitrogen, metabolites and the inhibitor influenced the effect of Cd on glutamine synthetase activity. The % inhibition of activity caused by Cd was higher with NO3<sup style='margin-left:-6px;'>- but lower with NH4<sup style='margin-left:-6px;'>+. Glutamine, 2-oxoglutarate, glutathione and sucrose decreased the % inhibition by Cd with the more prominent effect with glutamine and sucrose. Methionine sulfoximine exerted a more prominent effect for + Cd enzyme at lower concentration. The results indicate the involvement of reciprocal effects of Cd on glutamine synthetase and glutamate dehydrogenase activities and also on NADH- and Fd-glutamate synthase activities. For the inhibitory effect of Cd on glutamine synthetase activity, NH4<sup style='margin-left:-6px;'>+, glutamine, 2-oxoglutarate, glutathione and sucrose exerted a protective effect with the sucrose being most effective.
基金supported by Foundation of Fujian Key Laboratory of Functional Aquafeed and Culture Environment Control(No.FACE20200003)111 Project(111-2-06)and Jiangsu province“Collaborative Innovation Center for Advanced Industrial Fermentation”industry development program.
文摘The biological treatment of wastewater with high concentrations of ammonia nitrogen has become a hot research issue,but there are limited reports on the mechanism of ammonia nitrogen utilization by microorganisms.In this paper,a transcriptomic approach was used to investigate the differences in gene expression at 500.0 mg/L(Amo 500)and 100.0 mg/L(Amo 100)ammonium concentrations to reveal the mechanism of ammonia nitrogen removal from water by Pseudomonas stutzeri F2.The transcriptome data showed 1015(459 up-regulated and 556 down-regulated)differentially expressed genes with functional gene annotation related to nitrogen source metabolism,glycolysis,tricarboxylic acid cycle,extracellular polysaccharide synthesis,energy conversion and transmembrane transport,revealing the metabolic process of ammonium nitrogen conversion to biological ni-trogen in P.stutzeri F2 through assimilation.To verify the effect of ammonium transporter protein(AmtB)of cell membrane on assimilation,a P.stutzeri F2-ΔamtB mutant strain was obtained by constructing a knockout plasmid(pK18mobsacB-ΔamtB),and it was found that the growth characteristics and ammonium removal rate of the mutant strain were significantly reduced at high ammonium concentration.The carbon source components and dissolved oxygen conditions were optimized after analyzing the transcriptome data,and the ammonium removal rate was increased from 41.23%to 94.92%with 500.0 mg/L ammonium concentration.The study of P.stutzeri F2 transcript level reveals the mechanism of ammonia nitrogen influence on microbial assimilation process and improvement strategy,which provides a new strategy for the treatment of ammonia nitrogen wastewater.
