Lotus japonicus Metabolic Profiling. Development of Gas Chromatography-Mass Spectrometry Resources for the Study of Plant-Microbe Interactions

• Published in: Plant physiology (Bethesda) 2005-04, Vol.137 (4), p.1302-1318
• Main Authors: Desbrosses, Guilhem G, Kopka, Joachim, Udvardi, Michael K
• Format: Article
• Language: English
• Subjects: Alfalfa; Amino acids; Biological and medical sciences; Classical genetics, quantitative genetics, hybrids; flowers; Fundamental and applied biological sciences. Psychology; Gas chromatography; Gas Chromatography-Mass Spectrometry - methods; Genetics; Genetics of eukaryotes. Biological and molecular evolution; Leaves; Legumes; Loteae - metabolism; Loteae - microbiology; Lotus; Lotus corniculatus var. japonicus; Lotus japonicus; mass spectral tag; Mass spectrometry; Mass spectroscopy; Medicago truncatula; Mesorhizobium loti; Metabolism; Metabolites; metabolome; metabolomics; Molecular biology; Nitrogen Fixation; nitrogen-fixing bacteria; Nodules; Phenotype; phenotypic variation; plant biochemistry; Plant roots; Plant Structures - metabolism; Plants; Plants Interacting with Other Organisms; Principal Component Analysis; Principal components analysis; Pteridophyta, spermatophyta; root nodules; roots; Symbiosis; symbiotic nitrogen fixation; tissue distribution; Vegetals
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.104.054957

Symbiotic nitrogen fixation (SNF) in legume root nodules requires differentiation and integration of both plant and bacterial metabolism. Classical approaches of biochemistry, molecular biology, and genetics have revealed many aspects of primary metabolism in legume nodules that underpin SNF. Functional genomics approaches, especially transcriptomics and proteomics, are beginning to provide a more holistic picture of the metabolic potential of nodules in model legumes like Medicago truncatula and Lotus japonicus. To extend these approaches, we have established protocols for nonbiased measurement and analysis of hundreds of metabolites from L. japonicus, using gas chromatography coupled with mass spectrometry. Following creation of mass spectral tag libraries, which represent both known and unknown metabolites, we measured and compared relative metabolite levels in nodules, roots, leaves, and flowers of symbiotic plants. Principal component analysis of the data revealed distinct metabolic phenotypes for the different organs and led to the identification of marker metabolites for each. Metabolites that were enriched in nodules included: octadecanoic acid, asparagine, glutamate, homoserine, cysteine, putrescine, mannitol, threonic acid, gluconic acid, glyceric acid-3-P, and glycerol-3-P. Hierarchical cluster analysis enabled discrimination of 10 groups of metabolites, based on distribution patterns in diverse Lotus organs. The resources and tools described here, together with ongoing efforts in the areas of genome sequencing, and transcriptome and proteome analysis of L. japonicus and Mesorhizobium loti, should lead to a better understanding of nodule metabolism that underpins SNF.