State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, China.
Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.
mBio. 2021 May 11;12(3):e03671-20. doi: 10.1128/mBio.03671-20.
has 11 putative β-glucosidases in its genome, playing key parts in the induction and production of cellulase. Nevertheless, the reason why the genome encodes so many β-glucosidases and the distinct role each β-glucosidase plays in cellulase production remain unknown. In the present study, the cellular function and distribution of 10 known β-glucosidases (CEL3B, CEL3E, CEL3F, CEL3H, CEL3J, CEL1A, CEL3C, CEL1B, CEL3G, and CEL3D) were explored in , leaving out BGL1 (CEL3A), which has been well investigated. We found that the overexpression of or significantly enhanced extracellular β-glucosidase production, whereas the overexpression of severely inhibited cellulase production by cellulose, resulting in nearly no growth of Four types of cellular distribution patterns were observed for β-glucosidases in : (i) CEL3B, CEL3E, CEL3F, and CEL3G forming clearly separated protein secretion vesicles in the cytoplasm; (ii) CEL3H and CEL3J diffusing the whole endomembrane as well as the cell membrane with protein aggregation, like a reticular network; (iii) CEL1A and CEL3D in vacuoles; (iv) and CEL3C in the nucleus. β-glucosidases CEL1A, CEL3B, CEL3E, CEL3F, CEL3G, CEL3H, and CEL3J were identified as extracellular, CEL3C and CEL3D as intracellular, and CEL1B as unknown. The extracellular β-glucosidases CEL3B, CEL3E, CEL3F, CEL3H, and CEL3G were secreted through a tip-directed conventional secretion pathway, and CEL1A, via a vacuole-mediated pathway that was achieved without any signal peptide, while CEL3J was secreted via an unconventional protein pathway bypassing the endoplasmic reticulum (ER) and Golgi. Although β-glucosidases play an important role in fungal cellulase induction and production, our current understanding does not provide a global perspective on β-glucosidase function. This work comprehensively studies all the β-glucosidases regarding their effect on cellulase production and their cellular distribution and secretion. Overexpression of or significantly enhanced β-glucosidase production, whereas overexpression of severely inhibited cellulase production on cellulose. In addition, overexpression of , , , , , , or delayed endoglucanase (EG) production. We first identified four cellular distribution patterns of β-glucosidases in Specially, CEL3C was located in the nucleus. CEL3J was secreted through the nonclassical protein secretion pathway bypassing endoplasmic reticulum (ER) and Golgi. CEL1A was secreted via a vacuole-mediated conventional secretion route without a signal peptide. These findings advance our understanding of β-glucosidase properties and secretory pathways in filamentous fungi, holding key clues for future study.
该基因有 11 个推定的β-葡萄糖苷酶，在纤维素酶的诱导和生产中起着关键作用。然而，为什么基因组编码这么多β-葡萄糖苷酶，以及每种β-葡萄糖苷酶在纤维素酶生产中的独特作用仍然未知。在本研究中，探索了 10 种已知β-葡萄糖苷酶（CEL3B、CEL3E、CEL3F、CEL3H、CEL3J、CEL1A、CEL3C、CEL1B、CEL3G 和 CEL3D）在中的细胞功能和分布，不包括 BGL1（CEL3A），因为它已经得到了很好的研究。我们发现，或的过表达显著增强了细胞外β-葡萄糖苷酶的产生，而的过表达严重抑制了纤维素对纤维素酶的产生，导致的生长几乎没有。观察到 中β-葡萄糖苷酶有四种细胞分布模式：（i）CEL3B、CEL3E、CEL3F 和 CEL3G 在细胞质中形成明显分离的蛋白分泌小泡；（ii）CEL3H 和 CEL3J 在整个内质网以及细胞膜上扩散，形成蛋白聚集，呈网状；（iii）CEL1A 和 CEL3D 在液泡中；（iv）CEL3C 在核中。β-葡萄糖苷酶 CEL1A、CEL3B、CEL3E、CEL3F、CEL3G 被鉴定为细胞外，CEL3C 和 CEL3D 为细胞内，CEL1B 为未知。细胞外β-葡萄糖苷酶 CEL3B、CEL3E、CEL3F、CEL3H 和 CEL3G 通过尖端定向的常规分泌途径分泌，CEL1A 通过没有信号肽的液泡介导途径分泌，而 CEL3J 通过绕过内质网（ER）和高尔基体的非常规蛋白途径分泌。尽管β-葡萄糖苷酶在真菌纤维素酶的诱导和生产中起着重要作用，但我们目前的理解并没有提供β-葡萄糖苷酶功能的全局视角。这项工作全面研究了所有β-葡萄糖苷酶对纤维素酶产生及其细胞分布和分泌的影响。或的过表达显著提高了β-葡萄糖苷酶的产生，而过表达则严重抑制了纤维素酶在纤维素上的产生。此外，过表达、、、、、、或会延迟内切葡聚糖酶（EG）的产生。我们首次在 中鉴定了β-葡萄糖苷酶的四种细胞分布模式。特别地，CEL3C 位于细胞核中。CEL3J 通过绕过内质网（ER）和高尔基体的非经典蛋白分泌途径分泌。CEL1A 通过没有信号肽的液泡介导的常规分泌途径分泌。这些发现提高了我们对丝状真菌中β-葡萄糖苷酶性质和分泌途径的理解，为未来的研究提供了关键线索。
