title: Isolation and characterization of a novel ammonium overly sensitive mutant, amos2, in Arabidopsis thaliana.
abstract: Ammonium (NH(4)(+)) toxicity is a significant agricultural problem globally, compromising crop growth and productivity in many areas. However, the molecular mechanisms of NH(4)(+) toxicity are still poorly understood, in part due to a lack of valuable genetic resources. Here, a novel Arabidopsis mutant, amos2 (ammonium overly sensitive 2), displaying hypersensitivity to NH(4) (+) in both shoots and roots, was isolated. The mutant exhibits the hallmarks of NH(4)(+) toxicity at significantly elevated levels: severely suppressed shoot biomass, increased leaf chlorosis, and inhibition of lateral root formation. Amos2 hypersensitivity is associated with excessive NH(4)(+) accumulation in shoots and a reduction in tissue potassium (K(+)), calcium (Ca(2+)), and magnesium (Mg(2+)). We show that the lesion is specific to the NH(4)(+) ion, is independent of NH(4)(+) metabolism, and can be partially rescued by elevated external K(+). The amos2 lesion was mapped to a 16-cM interval on top of chromosome 1, where no similar mutation has been previously mapped. Our study identifies a novel locus controlling cation homeostasis under NH(4)(+) stress and provides a tool for the future identification of critical genes involved in the development of NH(4)(+) toxicity.
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, No 71 East Beijing Road, Nanjing 210008, China.
authors.forename: Guangjie
authors.initials: G
authors.lastname: Li
authors.forename: Gangqiang
authors.initials: G
authors.lastname: Dong
authors.forename: Baohai
authors.initials: B
authors.lastname: Li
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.forename: Herbert J
authors.initials: HJ
authors.lastname: Kronzucker
authors.forename: Weiming
authors.initials: W
authors.lastname: Shi
mesh_terms: D000645:Ammonium Sulfate / Q000378:metabolism / Q000494:pharmacology*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D003433:Crosses, Genetic; D003470:Culture Media / Q000378:metabolism; D017343:Genes, Plant; D006706:Homeostasis; D008274:Magnesium / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D010935:Plant Diseases / Q000139:chemically induced; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D003470:Culture Media; D000644:Quaternary Ammonium Compounds; C034007:ammonium bisulfate; D008274:Magnesium; D011188:Potassium; D000645:Ammonium Sulfate; D002118:Calcium