TY - JOUR
T1 - The transcriptional activator ClrB is crucial for the degradation of soybean hulls and guar gum in Aspergillus niger
AU - Kun, Roland S
AU - Garrigues, Sandra
AU - Peng, Mao
AU - Keymanesh, Keykhosrow
AU - Lipzen, Anna
AU - Ng, Vivian
AU - Tejomurthula, Sravanthi
AU - Grigoriev, Igor V
AU - de Vries, Ronald P
N1 - Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.
PY - 2023/3
Y1 - 2023/3
N2 - Low-cost plant substrates, such as soybean hulls, are used for various industrial applications. Filamentous fungi are important producers of Carbohydrate Active enZymes (CAZymes) required for the degradation of these plant biomass substrates. CAZyme production is tightly regulated by several transcriptional activators and repressors. One such transcriptional activator is CLR-2/ClrB/ManR, which has been identified as a regulator of cellulase and mannanase production in several fungi. However, the regulatory network governing the expression of cellulase and mannanase encoding genes has been reported to differ between fungal species. Previous studies showed that Aspergillus niger ClrB is involved in the regulation of (hemi-)cellulose degradation, although its regulon has not yet been identified. To reveal its regulon, we cultivated an A. niger ΔclrB mutant and control strain on guar gum (a galactomannan-rich substrate) and soybean hulls (containing galactomannan, xylan, xyloglucan, pectin and cellulose) to identify the genes that are regulated by ClrB. Gene expression data and growth profiling showed that ClrB is indispensable for growth on cellulose and galactomannan and highly contributes to growth on xyloglucan in this fungus. Therefore, we show that A. niger ClrB is crucial for the utilization of guar gum and the agricultural substrate, soybean hulls. Moreover, we show that mannobiose is most likely the physiological inducer of ClrB in A. niger and not cellobiose, which is considered to be the inducer of N. crassa CLR-2 and A. nidulans ClrB.
AB - Low-cost plant substrates, such as soybean hulls, are used for various industrial applications. Filamentous fungi are important producers of Carbohydrate Active enZymes (CAZymes) required for the degradation of these plant biomass substrates. CAZyme production is tightly regulated by several transcriptional activators and repressors. One such transcriptional activator is CLR-2/ClrB/ManR, which has been identified as a regulator of cellulase and mannanase production in several fungi. However, the regulatory network governing the expression of cellulase and mannanase encoding genes has been reported to differ between fungal species. Previous studies showed that Aspergillus niger ClrB is involved in the regulation of (hemi-)cellulose degradation, although its regulon has not yet been identified. To reveal its regulon, we cultivated an A. niger ΔclrB mutant and control strain on guar gum (a galactomannan-rich substrate) and soybean hulls (containing galactomannan, xylan, xyloglucan, pectin and cellulose) to identify the genes that are regulated by ClrB. Gene expression data and growth profiling showed that ClrB is indispensable for growth on cellulose and galactomannan and highly contributes to growth on xyloglucan in this fungus. Therefore, we show that A. niger ClrB is crucial for the utilization of guar gum and the agricultural substrate, soybean hulls. Moreover, we show that mannobiose is most likely the physiological inducer of ClrB in A. niger and not cellobiose, which is considered to be the inducer of N. crassa CLR-2 and A. nidulans ClrB.
KW - Aspergillus niger/genetics
KW - Glycine max/metabolism
KW - Transcription Factors/genetics
KW - Cellulose/metabolism
KW - Cellulase/metabolism
KW - Gene Expression Regulation, Fungal
KW - Fungal Proteins/genetics
U2 - 10.1016/j.fgb.2023.103781
DO - 10.1016/j.fgb.2023.103781
M3 - Article
C2 - 36801368
SN - 1087-1845
VL - 165
SP - 103781
JO - Fungal Genetics and Biology
JF - Fungal Genetics and Biology
ER -