Kurabayashi Kohei, Enshasy Hesham A El, Park Enoch Y, Kato Tatsuya
Department of Agriculture, Graduate School of Integrated Science and Technology, Shizuoka University, Ohya 836, Suruga-Ku, Shizuoka, Japan.
Innovation Centre in Agritechnology in Advanced Bioprocessing (ICA), Universiti Teknologi Malaysia, Higher Education Hup, Pagoh, Johor, Malaysia.
Arch Microbiol. 2025 Jun 5;207(7):167. doi: 10.1007/s00203-025-04359-3.
A filamentous fungus Ashbya gossypii overproduces riboflavin. However, what is a trigger to produce riboflavin in A. gossypii has not yet been elucidated. In the present study, we reveal the mechanism, by investigating riboflavin production in A. gossypii with respect to endoplasmic reticulum (ER) stresses. Addition of a reducing agent, dithiothreitol (DTT), to the culture medium at 10 mM resulted in more yellowish mycelia compared to the that of wild type strain, enhanced specific riboflavin production by approximately 1.7-fold, and an increase in the expression of several rib genes, AgRIB1, AgRIB2, and AgRIB7. Additionally, the production of reactive oxygen species (ROS) and expression of antioxidant genes, AgGLR1 and AgSOD1, were also induced. The ER stressor, tunicamycin, which inhibits the addition of N-glycan to glycoproteins in the ER, also enhanced the riboflavin production by 1.8 fold with the production of ROS and the increase of the expression of AgRIB3 and AgRIB4 genes. These results indicate that ER stress enhances riboflavin production in A. gossypii through the production of ROS; however, the mechanism of ER stress-induced riboflavin production has not yet been revealed. This study reveals why A. gossypii naturally overproduces riboflavin. This study shows the different mechanisms of the riboflavin over-production by ER stressors, DTT and tunicamycin. Additionally, cycloheximide, which inhibits protein synthesis and induces apoptosis, enhanced the riboflavin production. These results suggest that apoptosis induced by ER stresses may partially enhance the riboflavin production in A. gossypii. DTT and tunicamycin can be utilized to reveal why the riboflavin overproduction is conducted in A. gossypii, leading to the generation of riboflavin-hyperproducing A. gossypii mutants for efficient industrial riboflavin production.
丝状真菌棉阿舒囊霉能过量生产核黄素。然而，棉阿舒囊霉中产生核黄素的触发因素尚未阐明。在本研究中，我们通过研究棉阿舒囊霉中内质网（ER）应激下的核黄素产生情况，揭示了其机制。向培养基中添加10 mM的还原剂二硫苏糖醇（DTT），与野生型菌株相比，菌丝体颜色更黄，核黄素比产量提高了约1.7倍，并且几个核基因AgRIB1、AgRIB2和AgRIB7的表达增加。此外，活性氧（ROS）的产生以及抗氧化基因AgGLR1和AgSOD1的表达也被诱导。内质网应激剂衣霉素可抑制内质网中糖蛋白的N-聚糖添加，它也使核黄素产量提高了1.8倍，同时产生了ROS，并增加了AgRIB3和AgRIB4基因的表达。这些结果表明，内质网应激通过产生ROS增强了棉阿舒囊霉中核黄素的产生；然而，内质网应激诱导核黄素产生的机制尚未揭示。本研究揭示了棉阿舒囊霉天然过量生产核黄素的原因。这项研究展示了内质网应激剂DTT和衣霉素过量生产核黄素的不同机制。此外，抑制蛋白质合成并诱导细胞凋亡的环己酰亚胺增强了核黄素的产生。这些结果表明，内质网应激诱导的细胞凋亡可能部分增强了棉阿舒囊霉中核黄素的产生。DTT和衣霉素可用于揭示棉阿舒囊霉为何过量生产核黄素，从而产生用于高效工业生产核黄素的核黄素高产棉阿舒囊霉突变体。
