FluG affects secretion in colonies of Aspergillus niger

Abstract

Colonies of Aspergillus niger are characterized by zonal heterogeneity in growth, sporulation, gene expression and secretion. For instance, the glucoamylase gene glaA is more highly expressed at the periphery of colonies when compared to the center. As a consequence, its encoded protein GlaA is mainly secreted at the outer part of the colony. Here, multiple copies of amyR were introduced in A. niger. Most transformants over-expressing this regulatory gene of amylolytic genes still displayed heterogeneous glaA expression and GlaA secretion. However, heterogeneity was abolished in transformant UU-A001.13 by expressing glaA and secreting GlaA throughout the mycelium. Sequencing the genome of UU-A001.13 revealed that transformation had been accompanied by deletion of part of the fluG gene and disrupting its 3 0 end by integration of a transformation vector. Inactivation of fluG in the wild-type background of A. niger also resulted in breakdown of starch under the whole colony. Asexual development of the DfluG strain was not affected, unlike what was previously shown in Aspergillus nidulans. Genes encoding proteins with a signal sequence for secretion, including part of the amylolytic genes, were more often downregulated in the central zone of maltose-grown DfluG colonies and upregulated in the intermediate part and periphery when compared to the wild-type. Together, these data indicate that FluG of A. niger is a repressor of secretion.Keywords Fungus Á Conidiogenesis Á Asexual development Á Aspergillus fluG Á Secretion Á Heterogeneity Electronic supplementary material The online version of this article

FlbA-Regulated Gene rpnR Is Involved in Stress Resistance and Impacts Protein Secretion when Aspergillus niger Is Grown on Xylose

“…Downregulation of ribosomal protein genes has been shown to occur during sporulation in Aspergillus fumigatus (33), also supporting this theory. The facts that this ribosomal protein downregulation is dependent on BrlA (33) and that rpnR is also upregulated in zones of maltose-grown colonies lacking fluG (34) imply that downregulation of ribosomal proteins can be activated by several genes in the sporulation pathway. Taken together, the data show that the putative transcription factor RpnR of A. niger regulates proteotoxic-stress resistance and, possibly as a consequence, protein secretion and may therefore be an important target for improving A. niger as a cell factory for enzyme production.…”

Transcriptomic and molecular genetic analysis of the cell wall salvage response ofAspergillus nigerto the absence of galactofuranose synthesis

“…RNA‐Seq analysis was performed essentially as described previously (Wang et al, ) except for the transfer of genome annotations. Annotations were transferred from the CBS 513.88 genome to the N402 genome based on bidirectional alignments created with LAST (version 417) (Kiełbasa et al ., ), with tandem repeat sections masked with TRF (Benson, ).…”

Characterization of amylolytic enzyme overproducing mutant of <i>Aspergillus luchuensis</i> obtained by ion beam mutagenesis

“…The absence of transcriptional changes in genes encoding regulators for amylolytic enzymes was confirmed by RNA-seq analysis (Data Set S1 in supplemental file 1). AmyR regulates the transcription of genes encoding glycoside hydrolases such as aamA (acid-stable a-amylase), glaA (glucoamylase), and agdA (a-glucosidase) in A. niger (Yuan et al, 2008) Recently, the transcriptional regulator for asexual development FluG was shown to be involved in the expression of glucoamylase in A. niger (Wang et al, 2015). The transcriptional levels of an amyR homologous gene (AKAW_09854) and a fluG homologous gene (AKAW_05082) were unchanged in strain U1.…”