Transcriptome Analysis Reveals the Regulation of Aureobasidium pullulans under Different pH Stress

Abstract

Aureobasidium pullulans (A. pullulans), a commonly found yeast-like fungus, exhibits adaptability to a wide range of pH environments. However, the specific mechanisms and regulatory pathways through which A. pullulans respond to external pH remain to be fully understood. In this study, we first sequenced the whole genome of A. pullulans using Nanopore technology and generated a circle map. Subsequently, we explored the biomass, pullulan production, melanin production, and polymalic acid production of A. pullulans when cultivated at different pH levels. We selected pH 4.0, pH 7.0, and pH 10.0 to represent acidic, neutral, and alkaline environments, respectively, and examined the morphological characteristics of A. pullulans using SEM and TEM. Our observations revealed that A. pullulans predominantly exhibited hyphal growth with thicker cell walls under acidic conditions. In neutral environments, it primarily displayed thick-walled spores and yeast-like cells, while in alkaline conditions, it mainly assumed an elongated yeast-like cell morphology. Additionally, transcriptome analysis unveiled that A. pullulans orchestrates its response to shifts in environmental pH by modulating its cellular morphology and the expression of genes involved in pullulan, melanin, and polymalic acid synthesis. This research enhances the understanding of how A. pullulans regulates itself in diverse pH settings and offers valuable guidance for developing and applying engineered strains.