Transcription factor Agseb1 affects development, osmotic stress response, and secondary metabolism in marine-derived Aspergillus glaucus

Fungi possess sophisticated regulatory systems to respond to a vast array of environmental signals. Among these responsive networks, some genes play critical roles in the regulation of various cellular processes. Here, we identified a putative transcriptional factor Agseb1 in Aspergillus glaucus, a marine-derived filamentous fungus. Agseb1 encodes a protein with two C2H2 zinc fingers at the C-terminus, similar to the placement of these motifs in msn2/4 of Saccharomyces cerevisia, where they are positioned to allow binding to the CCCCT-box of stress-specific genes. Agseb1 similarly plays a role in stress response and its deletion mutant exhibited decreased sensitivity to hyperosmotic stress (both sorbitol and salt). Agseb1 is also important for mediating morphological development, because Agseb1 formed compact colonies and abnormal hyphal cells with hyperbranching at new sites. Consistent with the observed defects in conidial yield and sporulation, transcription analysis of the central asexual development pathway revealed significant activity changes. Additionally, the strain lacking Agseb1 exhibited a 43% decrease in aspergiolide A biosynthesis. Overall, Agseb1 has significant activity in different cellular pathways, the findings in this study may be generally applicable to the seb1 orthologs of other filamentous ascomycetes.