Regulatory roles of AmyR in amylolytic enzyme production, cellulose utilization, conidiation, stress tolerance, and fruit decay capacity of Aspergillus niger.

AmyR, a Zn(II)2Cys6 transcription factor, is a key regulator of carbohydrate-active enzyme production and oligosaccharide and polysaccharide utilization in filamentous fungi, but its roles in asexual development, environmental adaptation, and fruit spoilage remain unknown. This study aimed to characterize its functions using multi-phenotypic and transcriptional analyses in Aspergillus niger, a filamentous fungus widely used in fermentation and food processing, as well as a food spoilage and human pathogenic fungus. Deletion of amyR decreased amylolytic activity by repressing the expression of glucoamylase-ecoding gene glaA and six α-amylase genes. Intriguingly, ΔamyR exhibited higher carboxymethylcellulase activity and enhanced fungal growth on cellulose-containing media. Moreover, amyR deletion severely impaired conidiation, as indicated by reduced conidial yields, underdeveloped conidiophores, and downregulated transcription of conidiation-related genes. Additionally, amyR deletion had no significant effect on fungal tolerance to Congo red, but impaired tolerance to high osmotic and oxidative stresses and the ability to decay fruits. Overall, these findings revealed that beyond its canonical function in amylolytic metabolism, AmyR serves as a multifunctional regulator of cellulose utilization, asexual development, abiotic stress tolerance and fruit spoilage in A. niger, which expanding the known functions of amyR in filamentous fungi.