【正文】 ng negative correlations were found between glutamine concentrations in root extracts and both 13NH4+ influx rates and transcript levels. Model for the feedback regulation of the gene by N metabolites. wild type (Col0), the quadruple insertion line qko, and triple insertion lines expressing: AMT1。1 (qko+11), AMT1。2 (qko+12), AMT1。3 (qko+13), AMT2。1 (qko+21). amt1。2 lines was reduced by 18 to 26%. An amt1。1 amt1。2 amt1。3 amt2。1 quadruple mutant (qko) maintained only 5 to 10% of wildtype ammonium uptake capacity. AMT1。5 accounts for the remaining uptake capacity in qko. Ammonium substrate affinities of 50, 234, 61, and 181。M for AMT1。1, AMT1。2, AMT1。3, and AMT1。5, respectively, but no ammonium influx activity for AMT2。1. Lixing Yuan et al., Plant Cell 2022, 19:2636 Ammonium can enter the symplastic route for radial transport toward the root stele via AMT1。1, AMT1。3, and AMT1。5, which are localized at the plasma membrane of rhizodermis cells, including root hairs. Ammonium can also bypass outer root cells via the apoplastic transport route and subsequently enter the root symplast by AMT1。2mediated transport across the plasma membrane of endodermal (in the root hair zone) and cortical (in more basal root zones) cells. In the symplast, ammonium can either be assimilated into amino acids or loaded into the xylem by an as yet unidentified transport process. The contribution to ammonium uptake and spatial expression in root tissues of AMT1。1, AMT1。3, AMT1。5, and AMT1。2 under N deficiency. AMT1。1 = AMT1。3 AMT1。2 AMT1。5. 6 Assimilation of Ammonium GDH:谷氨酸脫氫酶 , GS:谷氨酰胺合成酶 , GOGAT:谷氨酸合成酶 Relative GOGAT activity levels in wildtype and FdGOGAT mutants (gls1). In higher plants, there are two forms of GOGAT, a Fd and an NADHdependent GOGAT, each of which is chloroplast localized. Two classes of GS isoenzymes were originally identified by ionexchange chromatography: cytosolic GS1 and chloroplastic GS2 . Chloroplastic GS2 is the predominant isoenzyme in leaves, it has been proposed to function in primary assimilation of ammonia reduced from nitrate in chloroplasts and/or in the reassimilation of photorespiratory ammonia . Cytosolic GS1 is the predominant isoenzyme in roots, it has been proposed to function in root nitrogen assimilation. Section 3 Nitrogen transfer in the arbuscular mycorrhizal symbiosis Arbuscular mycorrhizal fungi (AMF) are the most important ponent in agroecosystem as well as the most widespread fungi in soil ecosystem. Most land plants are symbiotic with AMF, which take up mineral nutrients from the soil and exchange them with plants for photosynthetically fixed carbon Model of N movement in AM symbiosis Inanic N is taken up by the fungal ERM and assimilated via NR and the GS–GOGAT cycle and is then converted into arginine, which is translocated along the hyphae from the ERM into the IRM. Arginine is broken down in the IRM, releasing urea and ornithine. Ammonia released from arginine breakdown passes to the host via AMT. Amino acids from ornithine breakdown and/or NH4+ assimilation in the IRM may be catabolized within the IRM or translocated to the ERM. Nature 2022, 435, 819823 Review Response of root 15NO3 influx and expression to localized supply of NO3 (Plants were grown for 6 weeks on 1 mm NO3 ) (a)one side in Nfree solution for 15 d , the other side remained on 1 mm NO3. (b) Time course of 15NO3 influx in both sides of the splitroot system after the beginning of localized starvation treatment. (c) Northern blot analysis of changes in transcript level Response of root 15NH4+ influx and expression to localized supply of NH4+ (Plants were grown for 5 weeks on 1 mm NO3, then for 1 week on 1 mm NH4+. (a) one side was supplied with Nfree solution for 15 d, the other side (+NH4+) remained on 1 mm NH4 (b) Time course of 15NH4+ influx. (c) Northern blot analysis of changes in transcript level. Changes in and expression in NO3 and NH4+fed roots of the same plant in response to localized N starvation. (a) Plants separated into three parts. (b) Northern blot analysis of expression. (c) Northern blot analysis of expression. Northern blot analysis of expression of and in 6weekold G39。43 doubleNR mutant plants after transfer from 1 mM NH4NO3 to either 1 mM or mM NO3. Genes involved in regulating N remobilization in senescing leaves, grain (seed) development, harvest index (HI), N harvest index (NHI), and grain yield