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Published on May 8, 2008; 10.1104/pp.108.118125

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Received February 19, 2008
Accepted April 22, 2008

The Arabidopsis Halophytic Relative, Thellungiella halophila, Tolerates Nitrogenlimiting Conditions by Maintaining Growth, Nitrogen Uptake and Assimilation

Surya Kant , Yong-Mei Bi , Elizabeth Weretilnyk , Simon Barak , and Steven J. Rothstein *

Department of Molecular and Cellular Biology, College of Biological Science, University of Guelph, Guelph, ON, Canada N1G 2W1; Department of Biology, McMaster University, Hamilton, ON, L8S 4K1; Albert Katz Department of Dryland Biotechnologies, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, 84990, Israel

* Corresponding author; email: rothstei{at}uoguelph.ca.

A comprehensive knowledge of mechanisms regulating nitrogen use efficiency (NUE) is required to reduce excessive input of nitrogen (N) fertilizers while maintaining acceptable crop yields under limited nitrogen supply. Studying plant species which are naturally adapted to low nitrogen conditions could facilitate identification of novel regulatory genes conferring better NUE. Here we show that Thellungiella halophila, a halophytic relative of Arabidopsis thaliana grows better than Arabidopsis under moderate (1 mM nitrate) and severe (0.4 mM nitrate) N-limiting conditions. Thellungiella exhibited a lower carbon to nitrogen ratio than Arabidopsis under N-limitation which was due to Thellungiella plants possessing higher nitrogen content, total amino acids, total soluble protein and lower starch content compared to Arabidopsis. Furthermore, Thellungiella had higher amounts of several metabolites such as soluble sugars and organic acids under N-sufficient conditions (4 mM nitrate). Nitrate reductase activity and NR2 gene expression in Thellungiella displayed less of a reduction in response to N-limitation than in Arabidopsis. Thellungiella shoot GS1 expression was more induced by low-N than in Arabidopsis, while in roots, Thellungiella GS2 expression was maintained under N-limitation whereas it decreased in Arabidopsis. Up-regulation of NRT2.1 and NRT3.1 expression was higher and repression of NRT1.1 was lower in Thellungiella roots under N-limiting conditions compared to Arabidopsis. Differential transporter gene expression was correlated with higher nitrate influx in Thellungiella at low 15NO3- supply. Taken together, our results suggest that Thellungiella is tolerant to N-limited conditions and could act as a model system to unravel the mechanisms for low nitrogen tolerance.






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