Three genes specifically expressed during phosphate deficiency in Pholiota nameko strain N2 encode hydrophobins

We previously isolated 31 cDNAs corresponding to pdi [inorganic phosphate (Pi) deficiency- inducible] genes through the differential screening of a cDNA library constructed from the mycelium of Pholiota nameko strain N2 cultured in Pi-depleted medium. Among the cDNAs, pdi251, pdi263 and pdi315 were analyzed here. The deduced amino acid sequences of pdi251, pdi263 and pdi315 showed high similarity to fungal hydrophobins and genes corresponding to these cDNAs encoding P. nameko hydrophobins were designated pnh1, pnh2 and pnh3, respectively. PNH1, PNH2 and PNH3 had a conserved spacing of eight cysteine residues in hydrophobins and a hydropathy pattern characteristic of class I hydrophobins. Phylogenetic analysis showed that PNH1, PNH2 and PNH3 were phylogenetically similar and significantly related to the hydrophobin POH1 specifically expressed in fruiting bodies of Pleurotus ostreatus. Northern blot analysis indicated that, under conditions of Pi deficiency, pnh2 and pnh3 were also induced in strains N4 and N301.