title: The Different Roles ofPenicillium oxalicumLaeA in the Production of Extracellular Cellulase and β-xylosidase.
abstract: Cellulolytic enzyme hydrolysis of lignocellulose biomass to release fermentable sugars is one of the key steps in biofuel refining. Gene expression of fungal cellulolytic enzymes is tightly controlled at the transcriptional level. Key transcription factors such as activator ClrB/CLR2 and XlnR/XYR1, as well as repressor CreA/CRE1 play crucial roles in this process. The putative protein methyltransferase LaeA/LAE1 has also been reported to regulate the gene expression of the cellulolytic enzyme. The formation and gene expression of the cellulolytic enzyme was compared amongPenicillium oxalicumwild type (WT) and seven mutants, including ΔlaeA(deletion oflaeA), OEclrB(clrBoverexpression), OEclrBΔlaeA(clrBoverexpression with deletion oflaeA), OExlnR(xlnRoverexpression), OExlnRΔlaeA(xlnRoverexpression with deletion oflaeA), ΔcreA(deletion ofcreA), and ΔcreAΔlaeA(double deletion ofcreAandlaeA). Results revealed that LaeA extensively affected the expression of glycoside hydrolase genes. The expression of genes that encoded the top 10 glycoside hydrolases assayed in secretome was remarkably downregulated especially in later phases of prolonged batch cultures by the deletion oflaeA. Cellulase synthesis of four mutants ΔlaeA, OEclrBΔlaeA, OExlnRΔlaeA, and ΔcreAΔlaeAwas repressed remarkably compared with their parent strains WT, OEclrB, OExlnR, and ΔcreA, respectively. The overexpression ofclrBorxlnRcould not rescue the impairment of cellulolytic enzyme gene expression and cellulase synthesis when LaeA was absent, suggesting that LaeA was necessary for the expression of cellulolytic enzyme gene activated by ClrB or XlnR. In contrast to LaeA positive roles in regulating prominent cellulase and hemicellulase, the extracellular β-xylosidase formation was negatively regulated by LaeA. The extracellular β-xylosidase activities improved over 5-fold in the OExlnRΔlaeAmutant compared with that of WT, and the expression of prominent β-xylosidase genexyl3Awas activated remarkably. The cumulative effect of LaeA and transcription factor XlnR has potential applications in the production of more β-xylosidase.
authors.affiliation: State Key Lab of Microbial Technology and National Glycoengineering Research Center, Shandong UniversityJinan, China; Shandong Provincial Key Laboratory of Carbohydrate Chemistry and Glycobiology, Shandong UniversityJinan, China.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Lab of Microbial Technology and National Glycoengineering Research Center, Shandong University Jinan, China.
authors.forename: Xiaoju
authors.initials: X
authors.lastname: Zheng
authors.affiliation: State Key Lab of Microbial Technology and National Glycoengineering Research Center, Shandong University Jinan, China.
authors.forename: Xiujun
authors.initials: X
authors.lastname: Zhang
authors.affiliation: State Key Lab of Microbial Technology and National Glycoengineering Research Center, Shandong University Jinan, China.
authors.forename: Longfei
authors.initials: L
authors.lastname: Bao
authors.affiliation: State Key Lab of Microbial Technology and National Glycoengineering Research Center, Shandong University Jinan, China.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: State Key Lab of Microbial Technology and National Glycoengineering Research Center, Shandong University Jinan, China.
authors.forename: Yinbo
authors.initials: Y
authors.lastname: Qu
authors.affiliation: State Key Lab of Microbial Technology and National Glycoengineering Research Center, Shandong University Jinan, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.affiliation: State Key Lab of Microbial Technology and National Glycoengineering Research Center, Shandong UniversityJinan, China; Shandong Provincial Key Laboratory of Carbohydrate Chemistry and Glycobiology, Shandong UniversityJinan, China.
authors.forename: Yuqi
authors.initials: Y
authors.lastname: Qin
keywords: LaeA; Penicillium oxalicum; cellulase; transcription factor; β-xylosidase