Characterization of novel roles of a HMG-box protein PoxHmbB in biomass-degrading enzyme production by Penicillium oxalicum
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High-mobility group (HMG)-box proteins are involved in chromatin organization in eukaryotes, especially in sex determination and regulation of mitochondrial DNA compaction. Although a novel HMG-box protein, PoxHmbB, had been initially identified to be required for filter paper cellulase activity by Penicillium oxalicum, the biological roles of HMG-box proteins in biomass-degrading enzyme production have not been systematically explored. The P. oxalicum mutant ∆PoxHmbB lost 34.7–86.5% of cellulase (endoglucanase, p-nitrophenyl-β-cellobiosidase, and p-nitrophenyl-β-glucopyranosidase) activities and 60.3% of xylanase activity following Avicel induction, whereas it exhibited about onefold increase in amylase activity following soluble corn starch induction. Furthermore, ∆PoxHmbB presented delayed conidiation and hyphae growth. Transcriptomic profiling and real-time quantitative reverse transcription-PCR revealed that PoxHmbB regulated the expression of major genes encoding plant biomass-degrading enzymes such as PoxCel7A-2, PoxCel5B, PoxBgl3A, PoxXyn11B, and PoxGA15A, as well as those involved in conidiation such as PoxBrlA. In vitro binding experiments further confirmed that PoxHmbB directly binds to the promoter regions of these major genes. These results further indicate the diversity of the biological functions of HMG-box proteins and provide a novel and promising engineering target for improving plant biomass-degrading enzyme production in filamentous fungi.
KeywordsPenicillium oxalicum HMG-box protein Regulatory role Amylase Cellulase PoxHmbB
JXF designed and supervised the study, and was involved in data analysis and manuscript preparation. SZ co-supervised all the experiments, prepared and revised the manuscript. YRX carried out mutant construction, enzyme activity test, RT-qPCR, and EMSA. LHF was involved in recombinant expression and EMSA. XZL was involved in genomic DNA, RNA, and protein extraction. CXL performed transcriptomic data analysis. YSY and LSL were involved in mutant construction and data analysis. All authors have read and approved the final manuscript.
Compliance with ethical standards
This article does not contain any studies with human participants or animals performed by any of the authors.
Conflict of interest
The authors declare that they have no conflict of interest.
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