Hydrophobin Genes Involved in Formation of Aerial Hyphae and Fruit Bodies in Schizophyllum.

Abstract

Fungi typically grow by apical extension of hyphae that penetrate moist substrates. After establishing a branched feeding mycelium, the hyphae differentiate and grow away from the substrate into the air where they form various structures such as aerial hyphae and mushrooms. In the basidiomycete species Schizophyllum commune, we previously identified a family of homologous genes that code for small cysteine-rich hydrophobic proteins. We now report that the encoded hydrophobins are excreted in abundance into the culture medium by submerged feeding hyphae but form highly insoluble complexes in the walls of emerging hyphae. The Sc3 gene encodes a hydrophobin present in walls of aerial hyphae. The homologous Sc7 and Sc4 genes, which are regulated by the mating-type genes, encode hydrophobins present in walls of fruit body hyphae. The hydrophobins are probably instrumental in the emergence of these aerial structures.

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“…and dimorphic yeasts [23]. According to Wessels et al [24], who first named hydrophobins in 1991 and continued research on hydrophobins, these proteins are highly surface-active and self-assemble at hydrophilic-hydrophobic interfaces in order to form amphipathic membranes. This gives them the ability to lower water surface tension and take part in numerous functions in fungal growth and development.…”

“…Class I hydrophobins are insoluble in aqueous solutions but are soluble in strong acids (trifluoroacetic acid, TFA; formic acid). Class II hydrophobins are soluble in organic solvents (60% ethanol; 2% hot sodium dodecyl sulfate, SDS) [24,[27][28][29][30][31]. Szilvay et al [32] reported that hydrophobins can form monomers, dimers, and tetramers in hydrophilic solutions.…”

Isolation and Physical Characterization of Hydrophobin-Like Proteins (HLP) from Aerial Conidia of <i>Metarhizium Anisopliae</i> Var. <i>Anisopliae</i>

“…Hydrophobins are highly insoluble in hot SDS. These proteins can only be solubilised when treated with concentrated cold formic acid (Bidochka et al, 1995;de Vries et al, 1993;Wessels et al, 1991) and dissociated into monomers only after oxidizing all the eight cysteine residues to cysteic acid by the performic acid (Wessels et al, 1991) which only then can be observed in SDS-PAGE protein profile. The range of molecular masses observed from both of the FAE proteins isolated from M. anisopliae isolates in this study fell within the range of 13.0-17.0 kDA (Fig.…”

“…The reserved samples were then suspended in 1 mL of 98% formic acid (Merck, Germany) under sonicating water bath maintaining at not more than 10°C for 2 h. Subsequently, 2 mL of performic acid (Wessels et al, 1991) was added to the supernatant and stood for 4 h on ice. The purified proteins were further added with 2 mL of 45% sodium hydroxide (NaOH) and 1 mL of ultrapure water and left to stand overnight at 4°C for neutralization.…”

“…The functional features of hydrophobins are their ability to self-assemble at the hydrophobic-hydrophilic interfaces and vice versa, lowering down the water surface tension and configuration of coatings (Wösten et al, 1993;Lugones et al, 1999). They are highly insoluble even in 2% of hot Sodium Dodecyl Sulfate (SDS) and only can be dissolved in concentrated acid such as 100% trifluoroacetic acid or 98% formic acid (de Vries et al, 1993;Wessels et al, 1991). In nature, hydrophobins play an important role during the fungal development such as formation of aerial hyphae, protection coat for the spores and mediate the surface tension of the hydrophobic surface of the host cuticle during pathogenesis (Wösten and Wessels, 1997;Nakari-Setӓlӓ et al, 1997;Talbot, 1997).…”