GATA-type transcriptional factor Gat1 regulates nitrogen uptake and polymalic acid biosynthesis in polyextremotolerant fungus Aureobasidium pullulans.

Polymalic acid (PMA) is a novel biopolymer produced by the polyextremotolerant fungus Aureobasidium pullulans. In this study, a GATA-family transcriptional factor, Gat1, which regulates nitrogen uptake and PMA biosynthesis, was investigated. PMA production increased to 11.2% in the mutant overexpressing gat1 but decreased to 49.1% of the PMA titre when gat1 was knocked out from the genome of A. pullulans. Comparative transcriptome analysis of wild-type and mutant strains (∆gat1 and OE::gat1) revealed that 23 common differentially expressed genes were related to oxidative phosphorylation, ribosome biogenesis, and nitrogen metabolism. Under nitrogen-limited stress, regardless of the preferred nitrogen (glutamine, Gln) or non-preferred nitrogen (proline, Pro), 70% of Gat1 in the cells was located in the nucleus-cytoplasm, which resulted in an increase in nitrogen uptake and PMA biosynthesis regulation. Quantitative RT-PCR revealed that glucosekinase (GLK) in the glycolytic pathway and malate synthase (MLS) in the glyoxylate shunt pathway may be cross-regulated by Gat1 and nitrogen concentration (Gln or Pro), Therefore, glk was overexpressed in mutant strain (OE::gat1), which resulted in an increased PMA titre and yield of 12.6% and 13.0% respectively. These findings indicate that Gat1 may play an important role in the dual regulation of the nitrogen and carbon metabolisms in PMA biosynthesis.