Cell biology of the <i>Koji</i> mold <i>Aspergillus oryzae</i> (2024)

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“…We found that EE motility is required for efficient secretion of the A. oryzae major protein α-amylase, which is thought to be transported through ER and Golgi and mainly secreted from the hyphal tip 36 – 38 . A lack of EE motility resulted in less α-amylase secretion, probably due to disorganization of the Spitzenkörper, rather than to perturbed distribution of the ER and Golgi.…”

confidence: 95%

et al. 2017

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.

Polysaccharides are biopolymers made up of a large number of monosaccharides joined together by glycosidic bonds. Polysaccharides are widely distributed in nature: Some, such as peptidoglycan and cellulose, are the components that make up the cell walls of bacteria and plants, and some, such as starch and glycogen, are used as carbohydrate storage in plants and animals. Fungi exist in a variety of natural environments and can exploit a wide range of carbon sources. They play a crucial role in the global carbon cycle because of their ability to break down plant biomass, which is composed primarily of cell wall polysaccharides, including cellulose, hemicellulose, and pectin. Fungi produce a variety of enzymes that in combination degrade cell wall polysaccharides into different monosaccharides. Starch, the main component of grain, is also a polysaccharide that can be broken down into monosaccharides by fungi. These monosaccharides can be used for energy or as precursors for the biosynthesis of biomolecules through a series of enzymatic reactions. Industrial fermentation by microbes has been widely used to produce traditional foods, beverages, and biofuels from starch and to a lesser extent plant biomass. This review focuses on the degradation and utilization of plant homopolysaccharides, cellulose and starch; summarizes the activities of the enzymes involved and the regulation of the induction of the enzymes in well-studied filamentous fungi.

BackgroundGATA transcription factors (TFs) are transcriptional regulatory proteins that contain a characteristic type-IV zinc finger and recognize the conserved GATA motif in the promoter region. Previous studies demonstrate that GATA TFs are involved in the regulation of diverse growth processes and various environmental stimuli stresses. Although the analysis of GATA TFs involved in abiotic stress have been performed in model plants and some fungi, information regarding GATA TFs in A. oryzae is extremely poor.ResultsTherefore, we identified seven GATA TFs from A. oryzae 3.042 genome, and named AoAreA, AoAreB, AoLreA, AoLreB, AoNsdD, AoSreA in correspondence to fungal orthologs, including a novel AoSnf5 with 20-residue between the Cys-X2-Cys motifs which was found in Aspergillus for the first time. Six known A. oryzae GATA TFs were classified into six subgroups, while the novel AoSnf5 also clustered into NSDD subgroups together with AoNsdD in the NJ_tree of all Aspergillus GATA TFs. Conserved motifs demonstrated that GATA TFs with similar motif compositions clustered into one subgroup, which suggests they might have similar genetic functions and further confirms the accuracy of the phylogenetic relationship of Aspergillus GATA TFs. The expression patterns of seven A. oryzae GATA TFs exhibited diversity under temperature and salt stresses. The expression analyses of AoLreA and AoLreB demonstrates AoLreA mainly played role in salt stress and AoLreB did under temperature stress. AoSreA was shown to positively regulate the expression of AoCreA and might act as a negative regulator in temperature and high salt stress response. In addition, the AoNsdD, AoSnf5, AoAreB, and AoAreA strongly responsed to salt stresses, while AoAreB and AoAreA showed opposite expression trends at high temperature. Overall, the expression patterns of these A. oryzae GATA TFs under distinct environmental conditions provided useful information for the further analysis of GATA TFs in regulation of various abiotic stress in A. oryzae.ConclusionIn conclusion, the comprehensive analysis data of A. oryzae GATA TFs will provide insights into the critical role of A. oryzae GATA TFs in resistance to temperature and salt stresses in A. oryzae.