Xiao Fang Zhu1, Xiao Ying Dong1, Qi Wu1,2, Ren Fang Shen3,4. 1. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China. 2. University of Chinese Academy of Sciences, Beijing, 100049, China. 3. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China. rfshen@issas.ac.cn. 4. University of Chinese Academy of Sciences, Beijing, 100049, China. rfshen@issas.ac.cn.
Abstract
MAIN CONCLUSION: The accumulation of NH4+ in response to Fe deficiency plays a role not only in the remobilization of Fe from the root cell wall, but also in the transportation of Fe from root to shoot. Ammonium (NH4+) plays an important role in phosphorus-deficiency responses in rice, but its role in responses to Fe deficiency remains unknown. Here, we demonstrate that the accumulation of NH4+ plays a pivotal role when Arabidopsis thaliana plants are subject to Fe deficiency. The Arabidopsis amt1-3 mutant, which is defective in endogenous NH4+ sensing, exhibited increased sensitivity to Fe deficiency compared to WT (wild type; Col-0). In addition, exogenous application of NH4+ significantly alleviated Fe deficiency symptoms in plants. NH4+ triggers the production of nitric oxide (NO), which then induces ferric-chelate reductase (FCR) activity and accelerates the release of Fe from the cell wall, especially hemicellulose, thereby increasing the availability of soluble Fe in roots. NH4+ also increases soluble Fe levels in shoots by upregulating genes involved in Fe translocation, such as FRD3 (FERRIC REDUCTASE DEFECTIVE3) and NAS1 (NICOTIANAMINE SYNTHASE1), hence, alleviating leaf chlorosis. Overall, NH4+ plays an important role in the reutilization of Fe from the cell wall and the redistribution of Fe from root to shoot in Fe-deficient Arabidopsis, a process dependent on NO accumulation.
MAIN CONCLUSION: The accumulation of NH4+ in response to Fe deficiency plays a role not only in the remobilization of Fe from the root cell wall, but also in the transportation of Fe from root to shoot. Ammonium (NH4+) plays an important role in phosphorus-deficiency responses in rice, but its role in responses to Fe deficiency remains unknown. Here, we demonstrate that the accumulation of NH4+ plays a pivotal role when Arabidopsis thaliana plants are subject to Fe deficiency. The Arabidopsis amt1-3 mutant, which is defective in endogenous NH4+ sensing, exhibited increased sensitivity to Fe deficiency compared to WT (wild type; Col-0). In addition, exogenous application of NH4+ significantly alleviated Fe deficiency symptoms in plants. NH4+ triggers the production of nitric oxide (NO), which then induces ferric-chelate reductase (FCR) activity and accelerates the release of Fe from the cell wall, especially hemicellulose, thereby increasing the availability of soluble Fe in roots. NH4+ also increases soluble Fe levels in shoots by upregulating genes involved in Fe translocation, such as FRD3 (FERRIC REDUCTASE DEFECTIVE3) and NAS1 (NICOTIANAMINE SYNTHASE1), hence, alleviating leaf chlorosis. Overall, NH4+ plays an important role in the reutilization of Fe from the cell wall and the redistribution of Fe from root to shoot in Fe-deficient Arabidopsis, a process dependent on NO accumulation.
Authors: Hong-Qing Ling; Petra Bauer; Zsolt Bereczky; Beat Keller; Martin Ganal Journal: Proc Natl Acad Sci U S A Date: 2002-10-07 Impact factor: 11.205