基金The authors thank ProfMary Lou Guerinot (Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire) for providing IRT1 peptide antibody and for the critical reading of the manuscript. We are also grateful to Drs Zhentao Lin and Yongfu Fu (Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing) for providing the BiFC assay system and technical supporting. This work was supported by the National Natural Science Foundation of China (Grant nos, 30530460 and 30521001) and the Ministry of Science and Technology of China (Grant nos, 2005cb20904 and 2006AA 10A 105) and Chinese Academy of Sciences (Grant no. KSCX2-YW-N- 001) as well as by the Harvest Plus-China Program.