Function of a hydrophobin in growth and development, nitrogen regulation, and abiotic stress resistance of Ganoderma lucidum

Abstract

Fungal hydrophobins have many important physiological functions, such as maintaining hydrophobicity and affecting virulence, growth, and development. In Ganoderma lucidum, the molecular regulation mechanisms of hydrophobins in mushroom are unclear. In this study, we investigated a hydrophobin protein 1 (Hyd1) in G. lucidum, which belongs to the fungal Class I hydrophobins. The hyd1 gene was highly expressed during the formation of primordia, and expression was the lowest in fruiting bodies. Through the construction of hyd1 silenced strains, we found that primordia formation was not initiated in these strains. This finding indicated that Hyd1 played an important role in the development of G. lucidum. Second, AreA, a key transcription factor in nitrogen metabolism, negatively regulated the expression of hyd1. In an areA silenced strain, the expression of hyd1 increased by approximately 14-fold compared with that of the wild-type (WT) strain. Electrophoretic mobility shift assays (EMSA) indicated binding of AreA to the promoter of hyd1. Additionally, expression of hyd1 was determined in the presence of different nitrogen sources. Compared with that in the ammonia nitrogen source, the expression of hyd1 in nitrate nitrogen source significantly increased. Finally, we found that hyd1 plays important roles not only in nitrogen regulation but also in the resistance to other abiotic stresses. After silencing of hyd1, the resistance to heat, cell wall, and salt stresses decreased. Our findings reveal the important roles of Hyd1 in the development and resistance to abiotic stresses in G. lucidum and provide insights into the nitrogen regulation mechanism of hydrophobins in higher basidiomycetes.

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“…In Flammulina filiformi s, gene silencing of the hydrophobin hyd9 has obvious effects on primordia development (Tao et al 2019 ). Furthermore, in G. lucidum , it was reported that the hydrophobin Hyd1 is important for nitrogen regulation and resistance to heat, cell wall, and salt stresses (Qiao et al 2023 ). Based on these studies, hydrophobins are assumed to play important roles in the development of vegetative hyphae and fruiting bodies in many basidiomycetes.…”