Exploration and characterization of hypoxia-inducible endogenous promoters in Aspergillus niger

Aspergillus niger is widely used for the efficient production of organic acids and enzyme preparations. However, this organism lacks basic genetic elements for dynamic control, especially inducible promoters that can respond to specific environmental signals. Since these are desirable for better adaptation of fermentation to large-scale industrial production, herein, we have identified the two first hypoxia-inducible promoters in A. niger, PsrbB and PjhbA. Their performance under high or low oxygen conditions was monitored using two reporter proteins, green fluorescent protein (EGFP) and beta-glucuronidase (GUS). For comparison, basal expression of the general strong promoter PgpdA was lower than PsrbB but higher than PfhbA. However, under hypoxia, both promoters showed higher expression than under hyperoxia, and these values were also higher than those observed for PgpdA. For PsrbB, strength under hypoxia was similar to 2-3 times higher than under hyperoxia (for PjhbA, 3-9 times higher) and similar to 2.5-5 times higher than for PgpdA (for PjhbA, 2-3 times higher). Promoter truncation analysis showed that the PsrbB fragment -1024 to -588 bp is the core region that determines hypoxia response.

Automated summary

Aspergillus niger lacks basic genetic elements for dynamic control, with the identification of the first hypoxia-inducible promoters providing new insights into the organism's adaptability to low oxygen conditions. Promoter truncation analysis revealed core regions determining hypoxia response.