Role Of Signal Transduction Pathways In The Regulation Of Cellulase Synthesis In Trichoderma Reesei

Trichoderma reesei is the most important industrial cellulase-producing filamentous fungus Although it can secrete large amounts of cellulase and hemicellulase, but its production is far less than industrial requirements.In order to better understand the metabolic network of T.reesei producting cellulase and hemicellulase, now researchers have conducted extensive research on its molecular physiology, but the cellulase-regulating signal transduction processes in T.reesei are largely unknown.In the T.reesei, there are three different MAPKs pathway in Tmkl, Tmk2 and Tmk3, respectively with yeast in Fus3p, Slt2p and Hoglp corresponding to each other. Tmk2 is involved in sporulation and cell wall integrity maintenance.Tmk3 is involved in cell wall integrity maintenance, high osmolarity resistance and biosynthesis.Unlike Tmk2,Tmk3 also participates in the synthesis of cellulase.This paper is focused on Tmk1, explore its physiological function and the regulation of the synthesis of cellulase.The deletion of tmk1 in T. reesei was successfully carried out with homologous recombination,generating two parallel tmk1 deletion strains respectively named T. reesei △tmk1-1 and T. reesei A tmk1-2.The parent T. reesei TU-6 strain and the tmk1 deletion strains were grown on different carbon sources on the plate. It can be observed that △tmk1 strains form larger colonies in comparison with the parent strain. Atmk1 strains grow significantly better than the parent strain. Although no obvious difference was observed between T. reesei parent and tmk1 deletion strains in CR-supplemented plates, the growth of tmk1 deletion strains reduced significantly faster than T.reesei parent TU-6 strain when supplemented CFW concentration increases. These results suggest that the deletion of tmk1 leads to the damage of cell wall integrity.A larger clear zone was formed in the Avicel double layer plates on tmk1 deletion strain was grown in comparison with the T. reesei TU-6 parent strain. Growth and production analysis of T. reesei TU-6, △tmk1 grown in 3 L fermenters showed higher cellulase activity.These results clearly lead to the suggestion that the deletion of tmk1 leads to improved growth and cellulase formation in T. reesei.However, Tmkl is not involved in the regulation of cellulase transcription in T. reesei. With Tmk2 and Tmk3, this research of Tmk1 helps explain how MAPKs influence cellulase formation in T. reesei.In the signal transduction of T. reesei,the role of casein kinase Ⅱ is unclear. In this work,the lower expression strains of al in T. reesei was successfully carried out by Tet-on promoter,generating strains named al-tet.In order to study the physiological function of a catalytic subunit of CKII, CKIIal, the phenotypic features of T. reesei parent and al-tet strains were compared.A significantly slowed of growth on agar plates on different carbon sources was observed for al-tet in comparison to the parent TU-6.Furthermore,the number of generated spores on PDA plate are greatly reduced.In cellobiose, Avicel, glucose,such as for a single carbon source culture, compared with the TU-6 parent strain, al-tet strains of al expression decreased, at the same time crel and cellulase genes transcription have varying degrees of increase.This work reports novel unique functions of a CKII catalytic subunit and the physiological functions of al research helps to reveal CKII is how to control the synthesis of cellulase.