Quarantin Alessandra, Hadeler Birgit, Kröger Cathrin, Schäfer Wilhelm, Favaron Francesco, Sella Luca, Martínez-Rocha Ana Lilia
Molekulare Phytopathologie, Institut für Pflanzenwissenschaften und Mikrobiologie, Universität Hamburg, Hamburg, Germany.
Dipartimento Territorio e Sistemi Agro-Forestali (TESAF), Università degli Studi di Padova, Padova, Italy.
Front Microbiol. 2019 Apr 12;10:751. doi: 10.3389/fmicb.2019.00751. eCollection 2019.
Hydrophobins (HPs) are small secreted fungal proteins possibly involved in several processes such as formation of fungal aerial structures, attachment to hydrophobic surfaces, interaction with the environment and protection against the host defense system. The genome of the necrotrophic plant pathogen contains five genes encoding for HPs (FgHyd1-5). Single and triple FgHyd mutants were produced and characterized. A reduced growth was observed when the Δ and the three triple mutants including the deletion of FgHyd2 were grown in complete or minimal medium. Surprisingly, the growth of these mutants was similar to wild-type when grown under ionic, osmotic or oxidative stress conditions. All the mutant strains confirmed the ability to develop conidia and perithecia, suggesting that the FgHyds are not involved in normal development of asexual and sexual structures. A reduction in the ability of hyphae to penetrate through the water-air interface was observed for the single mutants Δ and Δ as well as for the triple mutants including the deletion of FgHyd2 and FgHyd3. Besides, Δ and the triple mutant Δ were also affected in the attachment to hydrophobic surface. Indeed, wheat infection experiments showed a reduction of symptomatic spikelets for Δ and Δ and the triple mutants only when spray inoculation was performed. This result could be ascribed to the affected ability of mutants deleted of FgHyd2 and FgHyd3 to penetrate through the water-air interface and to attach to hydrophobic surfaces such as the spike tissue. This hypothesis is strengthened by a histological analysis, performed by fluorescence microscopy, showing no defects in the morphology of infection structures produced by mutant strains. Interestingly, triple hydrophobin mutants were significantly more inhibited than wild-type by the treatment with a systemic triazole fungicide, while no defects at the cell wall level were observed.
疏水蛋白（HPs）是真菌分泌的小分子蛋白质，可能参与多个过程，如真菌气生结构的形成、与疏水表面的附着、与环境的相互作用以及抵御宿主防御系统。坏死性植物病原体的基因组包含五个编码HPs的基因（FgHyd1 - 5）。构建并表征了单基因和三基因FgHyd突变体。当Δ突变体以及包括缺失FgHyd2的三个三基因突变体在完全培养基或基本培养基中生长时，观察到生长受到抑制。令人惊讶的是，当在离子、渗透或氧化应激条件下生长时，这些突变体的生长与野生型相似。所有突变菌株都证实了产生分生孢子和子囊壳的能力，这表明FgHyds不参与无性和有性结构的正常发育。对于单基因突变体Δ和Δ以及包括缺失FgHyd2和FgHyd3的三基因突变体，观察到菌丝穿透水 - 气界面的能力下降。此外，Δ突变体和三基因突变体Δ在与疏水表面的附着方面也受到影响。事实上，小麦感染实验表明，只有在进行喷雾接种时，Δ和Δ突变体以及三基因突变体的症状小穗数才会减少。这一结果可能归因于缺失FgHyd2和FgHyd3的突变体穿透水 - 气界面并附着到疏水表面（如穗组织）的能力受到影响。通过荧光显微镜进行的组织学分析强化了这一假设，该分析表明突变菌株产生的感染结构形态没有缺陷。有趣的是，用系统性三唑类杀菌剂处理时，三疏水蛋白突变体比野生型受到的抑制明显更强，而在细胞壁水平未观察到缺陷。
