Novel transcription factor regulating cellulase expression and growth improvement in cellulolytic fungi

Talaromyces sp., as powerful cellulolytic fungi, display a nearly complete enzymatic system, which exhibits a complex regulatory system involving multiple transcription factors to control the expression of cellulase genes. However, there are fewer studies on the transcriptional regulatory factors of cellulase expression in Talaromyces sp. This study provides a basis for in-depth analysis of the transcription regulatory mechanism of Talaromyces endophyticus for cellulase expression, offering new ways for the preparation of fermented sugars using straw resources to produce high value-added products and biofuels.

In this study, a novel transcription factor was investigated for T. endophyticus NEAU-6 which was a high cellulase-producing strain. Results revealed that TeSrdA was nuclear protein, which was stably expressed in the nucleus. TeSrdA deletion caused a remarkable increase of the activities of FPase (121.1%), CMCase (36.6%), pNPCase (97.0%), β-glucosidase (75.1%) and Xylanase (98.4%). Microscopic analysis showed that ΔTeSrdA strains increased the length of the hyphae and the number of branching. Notably, TeSrdA deletion could accelerated the microbial growth, which was unlike most studies in which deletion of transcription factor led to the reduction of cell growth. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) analyses revealed that the expression of eg7A, cbh6A, bgl3A, xyl11A genes was up-regulated obviously in the ΔTeSrdA strain. Through Electrophoretic mobility shift assays (EMSA), we further discovered that the transcription factor TeSrdA regulated the transcription of eg7A, cbh6A, cbh6B, bgl3A, xyl11A and xyl11B by directly binding to the promoters of these enzyme genes, thereby repressing the cellulase production.

TeSrdA plays an important role by increasing hyphal branching, accelerating strain growth, and promoting cellulase and hemicellulase production. The novel transcription factor TeSrdA is of great significance for studying the transcriptional regulatory network related to enzyme production and growth of strains in Talaromyces sp.