title: Metabolite profiling reveals distinct changes in carbon and nitrogen metabolism in phosphate-deficient barley plants (Hordeum vulgare L.).
abstract: Plants modify metabolic processes for adaptation to low phosphate (P) conditions. Whilst transcriptomic analyses show that P deficiency changes hundreds of genes related to various metabolic processes, there is limited information available for global metabolite changes of P-deficient plants, especially for cereals. As changes in metabolites are the ultimate 'readout' of changes in gene expression, we profiled polar metabolites from both shoots and roots of P-deficient barley (Hordeum vulgare) using gas chromatography-mass spectrometry (GC-MS). The results showed that mildly P-deficient plants accumulated di- and trisaccharides (sucrose, maltose, raffinose and 6-kestose), especially in shoots. Severe P deficiency increased the levels of metabolites related to ammonium metabolism in addition to di- and trisaccharides, but reduced the levels of phosphorylated intermediates (glucose-6-P, fructose-6-P, inositol-1-P and glycerol-3-P) and organic acids (alpha-ketoglutarate, succinate, fumarate and malate). The results revealed that P-deficient plants modify carbohydrate metabolism initially to reduce P consumption, and salvage P from small P-containing metabolites when P deficiency is severe, which consequently reduced levels of organic acids in the tricarboxylic acid (TCA) cycle. The extent of the effect of severe P deficiency on ammonium metabolism was also revealed by liquid chromatography-mass spectrometry (LC-MS) quantitative analysis of free amino acids. A sharp increase in the concentrations of glutamine and asparagine was observed in both shoots and roots of severely P-deficient plants. Based on these data, a strategy for improving the ability of cereals to adapt to low P environments is proposed that involves alteration in partitioning of carbohydrates into organic acids and amino acids to enable more efficient utilization of carbon in P-deficient plants.
authors.affiliation: Australian Centre for Plant Functional Genomics, The University of Adelaide, Waite Campus, PMB1, Glen Osmond, South Australia, 5064, Australia. chunyuan.huang@adelaide.edu.au
authors.forename: Chun Y
authors.initials: CY
authors.lastname: Huang
authors.forename: Ute
authors.initials: U
authors.lastname: Roessner
authors.forename: Ira
authors.initials: I
authors.lastname: Eickmeier
authors.forename: Yusuf
authors.initials: Y
authors.lastname: Genc
authors.forename: Damien L
authors.initials: DL
authors.lastname: Callahan
authors.forename: Neil
authors.initials: N
authors.lastname: Shirley
authors.forename: Peter
authors.initials: P
authors.lastname: Langridge
authors.forename: Antony
authors.initials: A
authors.lastname: Bacic
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D050260:Carbohydrate Metabolism / Q000187:drug effects; D002244:Carbon / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D001467:Hordeum / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism*; D010710:Phosphates / Q000172:deficiency* / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D006109:Poaceae / Q000187:drug effects / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D000596:Amino Acids; D010710:Phosphates; D010940:Plant Proteins; D000644:Quaternary Ammonium Compounds; D012333:RNA, Messenger; D002244:Carbon; D009584:Nitrogen