Article

Carbohydrate and amino acid metabolism in Tuber borchii mycelium during glucose utilization: a (13)C NMR study.

Istituto di Chimica Biologica "Giorgio Fornaini," Università degli Studi di Urbino, Via A Saffi, 2, 61029 (PU), Urbino, Italy.
Fungal Genetics and Biology (Impact Factor: 3.26). 08/2003; 39(2):168-75. DOI: 10.1016/S1087-1845(03)00006-9
Source: PubMed

ABSTRACT The metabolism of [1-13C]glucose in the vegetative mycelium of the ectomycorrhizal ascomycete Tuber borchii was studied in order to characterize the biochemical pathways for the assimilation of glucose and amino acid biosynthesis. The pathways were characterized using nuclear magnetic resonance spectroscopy in conjunction with [1-13C]glucose labeling. The enzymes of mannitol cycle and ammonium assimilation were also evaluated. The majority of the 13C label was incorporated into mannitol and this polyol was formed via a direct route from absorbed glucose. Amino acid biosynthesis was also an important sink of assimilated carbon and 13C was mainly incorporated into alanine and glutamate. From this intramolecular 13C enrichment, it is concluded that pyruvate, arising from [1-13C]glucose catabolism, was used by alanine aminotransferase, pyruvate dehydrogenase and pyruvate carboxylase before entering the Krebs cycle. The transfer of 13C-labeled mycelium on [12C]glucose showed that mannitol, alanine, and glutamate carbon were used to synthesize glutamine and arginine that likely play a storage role.

0 Bookmarks
 · 
109 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The genome of the ectomycorrhizal ascomycete Tubermelanosporum has recently been published and this has given researchers unique opportunities to learn more about the biology of this precious edible fungus. The epigeous ascomycete lives in Mediterranean countries in symbiotic interaction with roots of broad-leaf trees such as oaks and hazel. A most important new finding was the single mating type locus in the genome that occurs with two alleles in natural populations. The life cycle is now confirmed to be heterothallic and the species is outcrossing. Unlike sexual development in the soil, mycorrhization of the roots by homokaryotic haploid mycelia is mating-type-independent. Gene regulation during mycorrhization and fruiting and environmental influences on it is now genome-wide addressed. Genome profiling for functions in specific metabolic pathways is undertaken. Insights in most enthralling features of tubers such as on odor formation are thus gained.
    Fungal Genetics and Biology 02/2011; 48(6):555-60. · 3.26 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: • Primary carbohydrate metabolism plays a special role related to carbon/nitrogen exchange, as well as metabolic support of fruiting body development, in ectomycorrhizal macrofungi. In this study, we used information retrieved from the recently sequenced Tuber melanosporum genome, together with transcriptome analysis data and targeted validation experiments, to construct the first genome-wide catalogue of the proteins supporting carbohydrate metabolism in a plant-symbiotic ascomycete. • More than 100 genes coding for enzymes of the glycolysis, pentose phosphate, tricarboxylic acid, glyoxylate and methylcitrate pathways, glycogen, trehalose and mannitol metabolism and cell wall precursor were annotated. Transcriptional regulation of these pathways in different stages of the T. melanosporum lifecycle was investigated using whole-genome oligoarray expression data together with real-time reverse transcription-polymerase chain reaction analysis of selected genes. • The most significant results were the identification of methylcitrate cycle genes and of an acid invertase, the first enzyme of this kind to be described in a plant-symbiotic filamentous fungus. • A subset of transcripts coding for trehalose, glyoxylate and methylcitrate enzymes was up-regulated in fruiting bodies, whereas genes involved in mannitol and glycogen metabolism were preferentially expressed in mycelia and ectomycorrhizas, respectively. These data indicate a high degree of lifecycle stage specialization for particular branches of carbohydrate metabolism in T. melanosporum.
    New Phytologist 10/2010; 189(3):751-64. · 6.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this study, the physiological functions of fungal mannitol metabolism in the pathogenicity and protection against environmental stresses were investigated in the necrotrophic fungus Alternaria brassicicola. Mannitol metabolism was examined during infection of Brassica oleracea leaves by sequential HPLC quantification of the major soluble carbohydrates and expression analysis of genes encoding two proteins of mannitol metabolism, i.e., a mannitol dehydrogenase (AbMdh), and a mannitol-1-phosphate dehydrogenase (AbMpd). Knockout mutants deficient for AbMdh or AbMpd and a double mutant lacking both enzyme activities were constructed. Their capacity to cope with various oxidative and drought stresses and their pathogenic behavior were evaluated. Metabolic and gene expression profiling indicated an increase in mannitol production during plant infection. Depending on the mutants, distinct pathogenic processes, such as leaf and silique colonization, sporulation, survival on seeds, were impaired by comparison to the wild-type. This pathogenic alteration could be partly explained by the differential susceptibilities of mutants to oxidative and drought stresses. These results highlight the importance of mannitol metabolism with respect to the ability of A. brassicicola to efficiently accomplish key steps of its pathogenic life cycle.
    Frontiers in Plant Science 01/2013; 4:131. · 3.60 Impact Factor

Full-text

View
15 Downloads
Available from
Jun 3, 2014