Evidence for a nitrate-independent function of the nitrate sensor NRT1.1 in Arabidopsis thaliana
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NRT1.1 is a putative nitrate sensor and is involved in many nitrate-dependent responses. On the other hand, a nitrate-independent function of NRT1.1 has been implied, but the clear-cut evidence is unknown. We found that NRT1.1 mutants showed enhanced tolerance to concentrated ammonium as sole N source in Arabidopsis thaliana. This unique phenotype was not observed in mutants of NLP7, which has been suggested to play a role in the nitrate-dependent signaling pathway. Our real-time PCR analysis, and evidence from a literature survey revealed that several genes relevant to the aliphatic glucosinolate-biosynthetic pathway were regulated via a nitrate-independent signal from NRT1.1. When taken together, the present study strongly suggests the existence of a nitrate-independent function of NRT1.1.
KeywordsAmmonium tolerance Ammonium toxicity Nitrate sensor NRT1.1
We thank Dr. M. Taira, Dr. H. Hirano, Dr. Y. Ohmori and Dr. Y. Yasuoka for the use of the real-time PCR system. This study was financially supported by the Sasakawa Scientific Research Grant from The Japan Science Society, and by the Ministry of Education, Science, Sports, and Culture (Nos. 1685101, 17770015).
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