title: Comparative metabolite profiling of two rice genotypes with contrasting salt stress tolerance at the seedling stage.
abstract: BACKGROUND
  Rice is sensitive to salt stress, especially at the seedling stage, with rice varieties differing remarkably in salt tolerance (ST). To understand the physiological mechanisms of ST, we investigated salt stress responses at the metabolite level.
  
  
  METHODS
  Gas chromatography-mass spectrometry was used to profile metabolite changes in the salt-tolerant line FL478 and the sensitive variety IR64 under a salt-stress time series. Additionally, several physiological traits related to ST were investigated.
  
  
  RESULTS
  We characterized 92 primary metabolites in the leaves and roots of the two genotypes under stress and control conditions. The metabolites were temporally, tissue-specifically and genotype-dependently regulated under salt stress. Sugars and amino acids (AAs) increased significantly in the leaves and roots of both genotypes, while organic acids (OAs) increased in roots and decreased in leaves. Compared with IR64, FL478 experienced greater increases in sugars and AAs and more pronounced decreases in OAs in both tissues; additionally, the maximum change in sugars and AAs occurred later, while OAs changed earlier. Moreover, less Na+ and higher relative water content were observed in FL478. Eleven metabolites, including AAs and sugars, were specifically increased in FL478 over the course of the treatment.
  
  
  CONCLUSIONS
  Metabolic responses of rice to salt stress are dynamic and involve many metabolites. The greater ST of FL478 is due to different adaptive reactions at different stress times. At early salt-stress stages, FL478 adapts to stress by decreasing OA levels or by quickly depressing growth; during later stages, more metabolites are accumulated, thereby serving as compatible solutes against osmotic challenge induced by salt stress.
authors.affiliation: Institute of Crop Sciences, National Key Facility for Crop Gene Resources and Genetic Improvement, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Xiuqin
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Institute of Crop Sciences, National Key Facility for Crop Gene Resources and Genetic Improvement, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Wensheng
authors.initials: W
authors.lastname: Wang
authors.affiliation: Institute of Crop Sciences, National Key Facility for Crop Gene Resources and Genetic Improvement, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Institute of Crop Sciences, National Key Facility for Crop Gene Resources and Genetic Improvement, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Jianli
authors.initials: J
authors.lastname: Deng
authors.affiliation: Institute of Crop Sciences, National Key Facility for Crop Gene Resources and Genetic Improvement, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Zhikang
authors.initials: Z
authors.lastname: Li
authors.affiliation: Institute of Crop Sciences, National Key Facility for Crop Gene Resources and Genetic Improvement, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Binying
authors.initials: B
authors.lastname: Fu
mesh_terms: D000222:Adaptation, Physiological; D005838:Genotype; D055432:Metabolomics; D012275:Oryza / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D012965:Sodium Chloride
chemical_list: D012965:Sodium Chloride