Regulation of Fungal Morphology, Conidiogenesis and Violet Pigment Synthesis by the Betalain Biosynthesis Pathway Genes in Aspergillus sydowii H-1

Abstract

The biosynthesis of antioxidant pigments, namely, betalains, has predominantly been found in Caryophyllales. The potential betalains biosynthesis was firstly explored in Aspergillus sydowii H-1 under controlled culture conditions. This study identified, knocked out, and overexpressed genes involved in the betanin biosynthesis and assessed the activities of tyrosinase, 45-DOPA dioxygenase and LigB. The results indicated these betanin biosynthesis pathway was crucial for colony morphology, conidiogenesis, stress response, and violet pigment synthesis. Moreover, AsDODA and AsLigB catalyzed the conversion of L-DOPA into 45-seco-DOPA, a key intermediate in the formation of betalamic acid in vitro. Additionally, transcription factors such as AsbHLH, AsMYB1R, and AsWD40 positively regulated the expression of betalain biosynthesis genes. This research provides new insights into the evolutionary origins of betalain-producing species, expanding the scope of betalain biosynthesis to include Aspergillus species. ImportanceTo date, betalains were restricted to plants of the order Caryophyllales, fungi of Basidiomycota and several types of bacteria. This study is the first to demonstrate the potential of Ascomycetes A. sydowii H-1 to synthesize betalains under controlled culture conditions, providing a detailed genetic and biological characterization of the associated genes and metabolic pathways. This finding demonstrates that betalain biosynthesis can be expanded to other Aspergillus.