| Congresso Brasileiro de Microbiologia 2023 | Resumo: 726-1 | ||||
Resumo:Trichoderma reesei is one of the major cellulase-producing industrial organisms and served as a model to understand the regulation mechanisms of cellulase formation. However, the signal transduction pathways induced by carbon sources in this filamentous fungus are largely unknown, making the study of this physiological process important for both industrial and scientific research. Mitogen-activated protein kinases (MAPKs) are ubiquitous proteins in eukaryotes and are involved in various functions such as sporulation, resistance to high osmolarity, secondary metabolism, stress response, and regulation of cellulase production in filamentous fungi. In T. reesei, there are three major classes of MAPKs: Tmk3, Tmk2, and Tmk1, which are homologous to Hog1p, Slt2p, and Fus3p, respectively, in yeast. In this work, the role of MAPK Tmk3 in T. reesei was investigated in the wild type (WT) strain QM6a. Deletion of the yeast Hog1p-like tmk3 in T. reesei strongly reduced growth on glucose in both solid and submerged media. The Δtmk3 strain showed an improvement in resistance to cell wall stress caused by Calcofluor White (20 µg/mL) and Congo Red (50 µg/mL). In addition, the Δtmk3 strain is more sensitive to osmotic stress induced by NaCl and sorbitol (0.2, 0.5, and 1M) comparade to WT. The role of Tmk3 in the degradation of sugarcane bagasse (SCB) by T. reesei was also investigated, and the results showed that deletion of tmk3 affected the transcription of cellulase-encoding genes. The expression of endoglucanase cel7b, β-glucosidase cel3a, and xylanase xyn1 was higher in the mutant compared to WT strain after 8 hours of culture. At the same time, the expression of cellobiohydrolase cel7a was lower in the mutant. After 24 hours of culture, the expression of these cellulases and hemicellulases was the same in Δtmk3 and WT strain, with the exception of endoglucanase cel7b, which had higher expression in the mutant. These results indicate that Tmk3 is important for regulating cellulase expression in the early stages of cultivation in SCB. Moreover, the Δtmk3 strain showed the same amounts of total protein secreted and CMCase, β-glucosidase, xylanase, and β-xylosidase activities as the WT strain during the 96-hour cultivation in SCB. These studies revealed novel physiological processes involving the mitogen-activated protein kinase Tmk3 and provide new insights into its function in osmolarity resistance, stress response, and cellulase production. Palavras-chave: cellulases, mitogen-activated protein kinase, osmolarity resistance, Tmk3, Trichoderma reesei Agência de fomento:Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP 2022/14399-1 and 2021/01580-7) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001 | |||||