Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany.
BMC Microbiol. 2011 Jan 13;11:10. doi: 10.1186/1471-2180-11-10.
Hydrophobins are small, cysteine rich, surface active proteins secreted by filamentous fungi, forming hydrophobic layers on the walls of aerial mycelia and spores. Hydrophobin mutants in a variety of fungi have been described to show 'easily wettable' phenotypes, indicating that hydrophobins play a general role in conferring surface hydrophobicity to aerial hyphae and spores.
In the genome of the grey mould fungus Botrytis cinerea, genes encoding three hydrophobins and six hydrophobin-like proteins were identified. Expression analyses revealed low or no expression of these genes in conidia, while some of them showed increased or specific expression in other stages, such as sclerotia or fruiting bodies. Bhp1 belongs to the class I hydrophobins, whereas Bhp2 and Bhp3 are members of hydrophobin class II. Single, double and triple hydrophobin knock-out mutants were constructed by consecutively deleting bhp1, bhp2 and bhp3. In addition, a mutant in the hydrophobin-like gene bhl1 was generated. The mutants were tested for germination and growth under different conditions, formation of sclerotia, ability to penetrate and infect host tissue, and for spore and mycelium surface properties. Surprisingly, none of the B. cinerea hydrophobin mutants showed obvious phenotypic defects in any of these characters. Scanning electron microscopy of the hydrophobic conidial surfaces did not reveal evidence for the presence of typical hydrophobin 'rodlet' layers.
These data provide evidence that in B. cinerea, hydrophobins are not involved in conferring surface hydrophobicity to conidia and aerial hyphae, and challenge their universal role in filamentous fungi. The function of some of these proteins in sclerotia and fruiting bodies remains to be investigated.
水蛋白是由丝状真菌分泌的一种小的、富含半胱氨酸的表面活性蛋白，在气生菌丝和孢子的细胞壁上形成疏水性层。 各种真菌中的水蛋白突变体已被描述为表现出“易润湿”表型，表明水蛋白在赋予气生菌丝和孢子表面疏水性方面发挥着一般作用。
在灰霉菌 Botrytis cinerea 的基因组中，鉴定出编码三种水蛋白和六种水蛋白样蛋白的基因。 表达分析表明，这些基因在分生孢子中低表达或不表达，而其中一些在其他阶段（如菌核或子实体）表达增加或特异性表达。 Bhp1 属于 I 类水蛋白，而 Bhp2 和 Bhp3 是 II 类水蛋白的成员。 通过连续缺失 bhp1、bhp2 和 bhp3，构建了单、双和三重水蛋白敲除突变体。 此外，还生成了一个水蛋白样基因 bhl1 的突变体。 对突变体进行了不同条件下的萌发和生长、菌核形成、穿透和感染宿主组织的能力以及孢子和菌丝表面特性的测试。 令人惊讶的是，在这些特性中，B. cinerea 的任何水蛋白突变体都没有表现出明显的表型缺陷。 疏水分生孢子表面的扫描电子显微镜观察没有显示存在典型的水蛋白“棒层”的证据。
这些数据提供的证据表明，在 B. cinerea 中，水蛋白不参与赋予分生孢子和气生菌丝表面疏水性，这挑战了它们在丝状真菌中的普遍作用。 这些蛋白质中的一些在菌核和子实体中的功能仍有待研究。
