Tbz1: a conserved truffle gene, expressed during the early stage of fruit body maturation

Truffles are hypogeous ectomycorrhizal fungi belonging to the Ascomycetes, within the species of the genera Tuber which have a great economical importance for the organoleptic properties of their fruit bodies. Morphological descriptions of truffle ascomata development are limited due to their hypogeous habitat: in fact only the mature ascomata produce the typical aroma recognized by trained dogs while the collection of immature truffles is fortuitous. In addition, symbiotic relationships are required for the development of the truffle fruit bodies, which cannot be produced in vitro. Despite some biochemical and molecular studies regarding Tuber borchii fruit body development the molecular mechanisms leading to differentiation and ascospore production remain elusive. We reported the characterization of the T. borchii Tbz1 gene showing a high homology with a zygote-cell-wall protein of the green alga C. reinhardtii (Matters & Goodenough, 1992). Tbz1 is a single copy gene expressed in the early stage of ascomata maturation and absent in the symbiotic tissue. The deduced protein sequence of Tbz1 has transmembrane helices and a signal peptide indicating a membrane localization of this protein. The homologous genes in Tuber puberulum (Tpz1), Tuber aestivum (Taz1) and Tuber brumale (Tbrz1) have been also found. Sequence analysis showed that these genes are identical which strongly suggests that the function of the coded protein has been conserved during the evolution of the truffles. Matters GL, Goodenough UW (1992) A gene/pseudogene tandem duplication encodes a cysteine-rich protein expressed during zygote development in Chlamydomonas reinhardtii.