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Nitrate assimilation in the forage legume Lotus japonicus L.

Prosser, Ian M. and Massonneau, Agnes and Smyth, Audra J. and Waterhouse, Rosi N. and Forde, Brian G. and Clarkson, David T. (2006) Nitrate assimilation in the forage legume Lotus japonicus L. Planta, 223 (4). pp. 821-834. ISSN 0032-0935

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Abstract

Nitrate assimilation in the model legume, Lotus japonicus, has been investigated using a variety of approaches. A gene encoding a nitrate-inducible nitrate reductase (NR) has been cloned and appears to be the only NR gene present in the genome. Most of the nitrate reductase activity (NRA) is found in the roots and the plant assimilates the bulk of its nitrogen in that tissue. We calculate that the observed rates of nitrate reduction are compatible with the growth requirement for reduced nitrogen. The NR mRNA, NRA and the nitrate content do not show a strong diurnal rhythm in the roots and assimilation continues during the dark period although export of assimilated N to the shoot is lower during this time. In shoots, the previous low NR activity may be further inactivated during the dark either by a phosphorylation mechanism or due to reduced nitrate flux coincident with a decreased delivery through the transpiration stream. From nitrate-sufficient conditions, the removal of nitrate from the external medium causes a rapid drop in hydraulic conductivity and a decline in nitrate and reduced-N export. Root nitrate content, NR and nitrate transporter (NRT2) mRNA decline over a period of 2 days to barely detectable levels. On resupply, a coordinated increase of NR and NRT2 mRNA, and NRA is seen within hours.

Item Type: Article
Journal or Publication Title: Planta
Uncontrolled Keywords: Diurnal - Legume - Lotus - Nitrate assimilation - Nitrate reductase - Nutrient deprivation
Subjects: Q Science > QH Natural history > QH301 Biology
Departments: Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 11067
Deposited By: Prof Brian G Forde
Deposited On: 30 Jul 2008 16:05
Refereed?: Yes
Published?: Published
Last Modified: 26 Jul 2012 14:56
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/11067

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