ORCID Profile
0000-0002-4260-8394
Current Organisation
Tohoku University
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Publisher: Wiley
Date: 05-10-2006
Publisher: Proceedings of the National Academy of Sciences
Date: 21-01-2014
Abstract: Morphological adjustment is an important strategy for survival of living organisms in challenging environments. Plasticity of the root system architecture is critical for nutrient acquisition in plants. Among the essential elements, nitrogen (N) strongly affects root development. This article uncovers a key signaling mechanism regulating the outgrowth of lateral roots and expansion of plant root systems. The mechanism demonstrated in this study suggests an important morphological strategy for plant survival in N-poor environments.
Publisher: Oxford University Press (OUP)
Date: 11-2010
Abstract: Root development is strongly affected by the plant's nutritional status and the external availability of nutrients. Employing split-root systems, we show here that local ammonium supply to Arabidopsis thaliana plants increases lateral root initiation and higher-order lateral root branching, whereas the elongation of lateral roots is stimulated mainly by nitrate. Ammonium-stimulated lateral root number or density decreased after ammonium or Gln supply to a separate root fraction and did not correlate with cumulative uptake of 15N-labeled ammonium, suggesting that lateral root branching was not purely due to a nutritional effect but most likely is a response to a sensing event. Ammonium-induced lateral root branching was almost absent in a quadruple AMMONIUM TRANSPORTER (qko, the amt1 amt1 amt1 amt2 mutant) insertion line and significantly lower in the amt1 -1 mutant than in the wild type. Reconstitution of AMT1 expression in the amt1 -1 or in the qko background restored higher-order lateral root development. By contrast, AMT1 , which shares similar transport properties with AMT1 , did not confer significant higher-order lateral root proliferation. These results show that ammonium is complementary to nitrate in shaping lateral root development and that stimulation of lateral root branching by ammonium occurs in an AMT1 -dependent manner.
Publisher: Oxford University Press (OUP)
Date: 08-2007
Abstract: The AMMONIUM TRANSPORTER (AMT) family comprises six isoforms in Arabidopsis thaliana. Here, we describe the complete functional organization of root-expressed AMTs for high-affinity ammonium uptake. High-affinity influx of 15N-labeled ammonium in two transposon-tagged amt1 lines was reduced by 18 to 26% compared with wild-type plants. Enrichment of the AMT1 protein in the plasma membrane and localization of AMT1 promoter activity in the endodermis and root cortex indicated that AMT1 mediates the uptake of ammonium entering the root via the apoplasmic transport route. An amt1 amt1 amt1 amt2 quadruple mutant (qko) showed severe growth depression under ammonium supply and maintained only 5 to 10% of wild-type high-affinity ammonium uptake capacity. Transcriptional upregulation of AMT1 in nitrogen-deficient rhizodermal and root hair cells and the ability of AMT1 to transport ammonium in yeast suggested that AMT1 accounts for the remaining uptake capacity in qko. Triple and quadruple amt insertion lines revealed in vivo ammonium substrate affinities of 50, 234, 61, and 4.5 μM for AMT1 , AMT1 , AMT1 , and AMT1 , respectively, but no ammonium influx activity for AMT2 . These data suggest that two principle means of achieving effective ammonium uptake in Arabidopsis roots are the spatial arrangement of AMT1-type ammonium transporters and the distribution of their transport capacities at different substrate affinities.
Publisher: Oxford University Press (OUP)
Date: 10-12-2008
DOI: 10.1093/PCP/PCN186
Location: No location found
No related grants have been discovered for Soichi Kojima.