Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Fukuoka, 812-8581, Japan.
Sci Rep. 2017 Nov 17;7(1):15757. doi: 10.1038/s41598-017-16163-1.
Recent research in filamentous fungi has revealed that the motility of an endocytic organelle early endosome (EE) has a versatile role in many physiological functions. Here, to further examine the motility of EEs in the industrially important fungus Aspergillus oryzae, we visualized these organelles via the Rab5 homolog AoRab5 and identified AoHok1, a putative linker protein between an EE and a motor protein. The Aohok1 disruptant showed retarded mycelial growth and no EE motility, in addition to an apical accumulation of EEs and peroxisomes. We further demonstrated that the Aohok1 disruptant exhibited less sensitivity to osmotic and cell wall stresses. Analyses on the protein secretory pathway in ΔAohok1 cells showed that, although distribution of the endoplasmic reticulum and Golgi was not affected, formation of the apical secretory vesicle cluster Spitzenkörper was impaired, probably resulting in the observed reduction of the A. oryzae major secretory protein α-amylase. Moreover, we revealed that the transcript level of α-amylase-encoding gene amyB was significantly reduced in the Aohok1 disruptant. Furthermore, we observed perturbed conidial and sclerotial formations, indicating a defect in cell differentiation, in the Aohok1 disruptant. Collectively, our results suggest that EE motility is crucial for α-amylase production and cell differentiation in A. oryzae.
最近对丝状真菌的研究表明，内吞细胞器早期内体（EE）的运动在许多生理功能中具有多种作用。在这里，为了进一步研究在工业上重要的真菌米曲霉中 EE 的运动，我们通过 Rab5 同源物 AoRab5 可视化了这些细胞器，并鉴定了 AoHok1，这是 EE 和运动蛋白之间的假定连接蛋白。Aohok1 缺失突变体表现出菌丝生长缓慢和 EE 运动性丧失，此外 EE 和过氧化物酶体在顶端积累。我们进一步证明，Aohok1 缺失突变体对渗透压和细胞壁应激的敏感性降低。对ΔAohok1 细胞中蛋白质分泌途径的分析表明，尽管内质网和高尔基体的分布不受影响，但顶端分泌囊泡簇 Spitzenkörper 的形成受损，可能导致观察到的米曲霉主要分泌蛋白α-淀粉酶减少。此外，我们发现 Aohok1 缺失突变体中编码基因 amyB 的转录水平显著降低。此外，我们观察到分生孢子和菌核形成受到干扰，表明细胞分化缺陷，在 Aohok1 缺失突变体中。总之，我们的结果表明 EE 运动对于米曲霉中α-淀粉酶的产生和细胞分化至关重要。
