Differential transcriptomic profiling of filamentous fungus during solid-state and submerged fermentation and identification of an essential regulatory gene PoxMBF1 that directly regulated cellulase and xylanase gene expression

Abstract

Background Solid-state fermentation (SSF) mimics the natural decay environment of soil fungi and can be employed to investigate the production of plant biomass-degrading enzymes. However, knowledge on the transcriptional regulation of fungal genes during SSF remains limited. Herein, transcriptional profiling was performed on the filamentous fungus Penicillium oxalicum strain HP7-1 cultivated in medium containing wheat bran plus rice straw (WR) under SSF (WR_SSF) and submerged fermentation (WR_SmF; control) conditions. Novel key transcription factors (TFs) regulating fungal cellulase and xylanase gene expression during SSF were identified via comparative transcriptomic and genetic analyses. Results Expression of major cellulase genes was higher under WR_SSF condition than that under WR_SmF, but the expression of genes involved in the citric acid cycle was repressed under WR_SSF condition. Fifty-six candidate regulatory genes for cellulase production were screened out from transcriptomic profiling of P . oxalicum HP7-1 for knockout experiments in the parental strain ∆ PoxKu70 , resulting in 43 deletion mutants including 18 constructed in the previous studies. Enzyme activity assays revealed 14 novel regulatory genes involved in cellulase production in P . oxalicum during SSF. Remarkably, deletion of the essential regulatory gene PoxMBF1 , encoding Multiprotein Bridging Factor 1, resulted in doubled cellulase and xylanase production at 2 days after induction during both SSF and SmF. PoxMBF1 dynamically and differentially regulated transcription of a subset of cellulase and xylanase genes during SSF and SmF, and conferred stress resistance. Importantly, PoxMBF1 bound specifically to the putative promoters of major cellulase and xylanase genes in vitro. Conclusions We revealed differential transcriptional regulation of P . oxalicum during SSF and SmF, and identified PoxMBF1, a novel TF that directly regulates cellulase and xylanase gene expression during SSF and SmF. These findings expand our understanding of regulatory mechanisms of cellulase and xylanase gene expression during fungal fermentation. Electronic supplementary material The online version of this article (10.1186/s13068-019-1445-4) contains supplementary material, which is available to authorized users.

Impacts of biofilms on the conversion of cellulose

“…Overall, a 10-fold cost reduction for cellulase production in solid-state fermentation compared to submerged fermentation has been estimated (Tengerdy 1996). Recently, Zhao et al (2019) performed transcriptomic profiling of the filamentous fungus Penicillium oxalicum during solid-state and submerged fermentation and demonstrated, that the expression of major cellulase genes was higher under solid state conditions, while genes involved in the citric acid cycle were downregulated.…”

Transcription Factor Atf1 Regulates Expression of Cellulase and Xylanase Genes during Solid-State Fermentation of Ascomycetes

“…Recently, we compared transcriptional profiles of Penicillium oxalicum strain HP7-1 cultivated in liquid and solid media containing the same carbon source, and the results indicated that SSF elevated the expression of major cellulase genes and repressed the expression of genes involved in the citric acid cycle compared with levels in SmF cultures. Subsequently, a key regulator, P. oxalicum MBF1 (PoxMBF1), was identified, which negatively affected the production of cellulase and xylanase of P. oxalicum during SSF as well as SmF (9). However, this information is insufficient to elucidate the regulatory mechanism of cellulase and xylanase gene expression under SSF.…”

Deletion of Atg22 gene contributes to reduce programmed cell death induced by acetic acid stress in Saccharomyces cerevisiae

“…Multiple efforts have been made to improve Ac resistance and elucidated mechanisms of stress resistance in yeast [4, 20, 21]. However, little attention is paid to the relationship between Ac resistance and atg22 , a small membrane-spanning protein on vacuole of S. cerevisiae .…”