A dehydration-inducible gene in the truffle Tuber borchii identifies a novel group of dehydrins

Bioinformatics tools, phylogenetic analysis and expression studies were used to support the hypothesis that this sequence, named TbDHN1, is the first dehydrin (DHN)-like coding gene isolated in fungi. Homologs of this gene, all defined as "coding for hypothetical proteins" in public databases, were exclusively found in ascomycetous fungi and in plants. Although complete (or almost complete) fungal genomes and EST collections of some Basidiomycota and Glomeromycota are already available, DHN-like proteins appear to be represented only in Ascomycota. A new and previously uncharacterized conserved signature pattern was identified and proposed to Uniprot database as the main distinguishing feature of this new group of DHNs. Expression studies provide experimental evidence of a transcript induction of TbDHN1 during cellular dehydration.Expression pattern and sequence similarities to known plant DHNs indicate that TbDHN1 is the first characterized DHN-like protein in fungi. The high similarity of TbDHN1 with homolog coding sequences implies the existence of a novel fungal/plant group of LEA Class II proteins characterized by a previously undescribed signature pattern.Hyperosmotic conditions and low temperatures cause cellular dehydration, i.e. removal of water from the cytoplasm into the extracellular space, resulting in the reduction of cytosolic volumes and the alteration of cellular mechanisms. Dehydrins (DHNs) are a group of heat-stable plant proteins believed to play a protective role during cellular dehydration [1,2]. They accumulate during dehydrative stress caused by or associated with low or freezing temperatures, drought, salinity, embryo desiccation and abscissic acid synthesis. Dehydrins are very rich in glycine residues, while cysteine and tryptophane are lacking or under-represented [3]. They are characterized by highly conserved 15-mer lysin rich sequences, called K-segments, which may be present one or several times, one or more Y-segments (DEYGNP) and/or