Zhang Jin-Guan, Xu Si-Yuan, Ying Sheng-Hua, Feng Ming-Guang
Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
J Invertebr Pathol. 2023 Nov;201:108006. doi: 10.1016/j.jip.2023.108006. Epub 2023 Oct 14.
Class I/II hydrophobins constitute a family of small amphiphilic proteins that mediate cell hydrophobicity and adhesion to host or substrata and have pleiotropic effects in filamentous fungi. Here we report that only class I Hyd1 is essential for conidial hydrophobicity and insect pathogenicity among three hydrophobins (Hyd1-3) characterized in Metarhizium robertsii, an insect-pathogenic fungus. Aerial conidiation levels of three Δhyd1 mutants were much more reduced in 5-day-old cultures than in 7-day-old cultures, which were wettable (hydrophilic), but restored to a wild-type level in 15-day-old cultures. The Δhyd1 mutants were compromised in conidial quality, including significant decreases in hydrophobicity (58%), adhesion to insect cuticle (36%), insect pathogenicity via normal cuticle infection (37%), UVB resistance (20%), and heat tolerance (10%). In contrast, none of all examined phenotypes were affected in the null mutants of hyd2 and hyd3. Intriguingly, micromorphology and integrity of hydrophobin rodlet bundles on conidial coat were not affected in all mutant and wild-type strains, but the rodlet bundles were disordered in the absence of hyd1, suggesting a link of the disorder to the decreased hydrophobicity. Therefore, Hyd1 mediates the fungal hydrophobicity and plays an important role in conidial quality control and insect-pathogenic lifecycle. Class I Hyd2 and class II Hyd3 seem functionally redundant in M. robertsii.
I/II类疏水蛋白构成了一类小的两亲性蛋白家族，它们介导细胞疏水性以及与宿主或基质的黏附，并在丝状真菌中具有多效性作用。在此我们报道，在昆虫病原真菌罗伯茨绿僵菌中鉴定的三种疏水蛋白（Hyd1 - 3）中，只有I类Hyd1对分生孢子疏水性和昆虫致病性至关重要。三个Δhyd1突变体在5日龄培养物中的气生分生孢子形成水平比在7日龄培养物中降低得更多，7日龄培养物是可湿性的（亲水的），但在15日龄培养物中恢复到野生型水平。Δhyd1突变体的分生孢子质量受损，包括疏水性显著降低（58%）、对昆虫表皮的黏附性降低（36%）、通过正常表皮感染的昆虫致病性降低（37%）、紫外线B抗性降低（20%）和耐热性降低（10%）。相比之下，hyd2和hyd3的缺失突变体中所有检测的表型均未受影响。有趣的是，所有突变体和野生型菌株分生孢子表面疏水蛋白小杆束的微观形态和完整性均未受影响，但在没有hyd1的情况下小杆束无序排列，这表明这种无序与疏水性降低有关。因此，Hyd1介导真菌疏水性，并在分生孢子质量控制和昆虫致病生命周期中发挥重要作用。I类Hyd2和II类Hyd3在罗伯茨绿僵菌中似乎功能冗余。
