Different temporal and spatial expression of two hydrophobin-encoding genes of the edible mushroom Agaricus bisporus

Abstract

In a search for genes that are only expressed in fruit bodies of the basidiomycete Agaricus bisporus, two cDNAs, hypA and hypB that encode hydrophobins have been isolated previously. In this study, the structure of hypB is resolved and it is shown that the two genes are differentially expressed, indicating that the encoded hydrophobins serve different functions in A. bisporus mushrooms. hypB encodes a polypeptide (HYPB) of 119 aa that shows little sequence identity with HYPA apart from the characteristic arrangement of eight cysteines found exclusively in hydrophobins. The temporal and spatial expression of the two hydrophobin-encoding genes during fruit body development was compared using Northern analysis and in situ hybridization. Accumulation of hypA mRNA was found in tissue fractions consisting of undifferentiated white hyphae. In situ hybridization showed that the highest hypA mRNA levels are not found in the outermost cell layers of the pileipellis but in the cell layers adjacent to that. The highest level of expression of hypB occurs early in development when the primordium differentiates into densely packed, randomly oriented cap hyphae and loosely packed, vertically oriented stipe hyphae. In mature mushrooms, a strong accumulation of hypB transcripts was found only in the transitional zone between cap and stipe tissue, demonstrating that transcription regulation of hype is clearly distinct from hypA. I I

Classification of Sequences Expressed during the Primordial and Basidiome Stages of the Cultivated Mushroom Agaricus bisporus

“…Whereas the hydrophobin B gene appears to be mostly expressed in basidiomes, high levels of hydrophobin A mRNA are observed in undifferentiated white hyphae and primordial stage (De Groot et al, 1999;Lugones et al, 1999). Our results suggest that EST 22, whose encoded product has 96% similarity with hydrophobin A, is expressed not only in primordia but also in basidiome tissue.…”

“…Hydrophobin-encoding genes are thought to have different temporal and spatial patterns of expression (De Groot et al, 1999). Whereas the hydrophobin B gene appears to be mostly expressed in basidiomes, high levels of hydrophobin A mRNA are observed in undifferentiated white hyphae and primordial stage (De Groot et al, 1999;Lugones et al, 1999).…”

“…Hydrophobins are cysteine-rich hydrophobic polypeptides that self-polymerize when exposed to hydrophilic-hydrophobic interfaces, giving rise to amphipathic layers (Lugones et al, 1998(Lugones et al, , 1999. Hydrophobins appear to have different temporal and spatial expression patterns (De Groot et al, 1999). Hydrophobin ABH1 covers the surface of the fruiting body of A. bisporus and lines air channels in the fruiting body (Lugones et al, 1996(Lugones et al, , 1999.…”

Monitoring the Metabolic State of Fungal Hyphae and the Presence of Melanin by Nonlinear Spectral Imaging

“…These data thus show that zones within the mushroom are heterogeneous with respect to metabolism and pigment formation. Such zonal heterogeneity was also shown previously with respect to gene expression (38)(39)(40)(41)(42)(43)(44) and protein accumulation (39) in A. bisporus. In fact, these processes can be heterogeneous even between neighboring hyphae within a mycelial zone (45)(46)(47)(48)(49).…”

Identification of a Hydrophobin Gene That is Developmentally Regulated in the Ectomycorrhizal Fungus Tricholoma terreum

“…However, at least one more hydrophobin is expected in T. terreum, based on additional signals in Southern blot analyses. For S. commune and Agaricus bisporus, three fruitbody-specific hydrophobins and two fruitbody-specific hydrophobins, respectively, are known in addition to a vegetative hydrophobin (6,23,30). Sequence similarity among hydrophobins usually are limited, which might mean that the cross-hybridizing hydrophobin is allelic to hyd1 rather than being a representative of other hydrophobins with probable different function (compare A. bisporus; 23).…”