Effetto della composizione del mezzo nutritivo sullo sviluppo dei miceli di Tuber spp.

http://www.agrsci.unibo.it/umi

Genomic profiling of carbohydrate metabolism in the ectomycorrhizal fungus Tuber melanosporum.

Primary carbohydrate metabolism plays a special role related to carbon ⁄ nitrogen exchange, as well as metabolic support of fruiting body development, in ecto- mycorrhizal 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 regu- lation 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 ectomycor- rhizas, respectively. These data indicate a high degree of lifecycle stage specializa- tion for particular branches of carbohydrate metabolism in T. melanosporum

Characterization and mRNA expression profile of the TbNre1 gene of the ectomycorrhizal fungus Tuber borchii

This study focuses on the cloning and characterization of the major nitrogen regulator element from the ectomycorrhizal fungus Tuber borchii, TbNre1. Sequence analysis of the predicted protein and complementation experiments in Neurospora crassa demonstrated that the cloned gene is orthologous to areA/nit-2 gene. Transcriptional expression investigations by real-time RT-PCR showed TbNre1 up-regulation in the presence of nitrate or in the absence of nitrogen during free-living mycelium growth. On the contrary, TbNre1 mRNA levels remained at basal values in the presence of preferred nitrogen sources like ammonium and glutamine. Furthermore, TbNre1 mRNA was found to be up-regulated during T. borchii and T. platyphyllos interaction. All these data suggest that the regulatory protein TBNRE1 could play a major role in regulating N metabolism genes of T. borchii in the free living mycelium and in T. borchii-T. platyphyllos interaction. Finally, the possible role of the transcription factor TBNRE1 in the induction of proteases and virulence-like genes, necessary in ectomycorrhizal establishment, was also discussed