Differences in the gene expressive quantities of carbonic anhydrase and cysteine synthase in the weathering of potassium-bearing minerals by Aspergillus niger

We investigated the differences in the gene expression of carbonic anhydrase (CA) and cysteine synthase (CysM) between two weathering conditions, with either soluble potassium or insoluble potassium. We cultured a strain of A. niger by adopting a variant Czapek medium (using Na₂HPO₄ as a substitute for K₂HPO₄) in two groups, Group A (containing silicate minerals bearing potassium but without KCl) and Group B (with KCl). We extracted the mRNAs of CA and CysM from these two groups and performed real-time quantitative polymerase chain reactions (RT-qPCR). We constructed relative standard curves by using glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as the reference to confirm a consistent amplification efficiency of the target genes (CA and CysM) and the reference gene and quantified the gene expression of the targets in a relative manner. Our results showed that CA and CysM in Group A were upregulated for 1.7 times and 11.7 times, respectively, compared with those in Group B. Furthermore, we also analyzed some metabolic pathways and functions of the A. niger-induced weathering of potassium-bearing minerals, which involved the synthesizing of these two enzymes. Thus our work provides materials for further study of the roles of A. niger in the metabolic regulation during the weathering process of potassium-bearing minerals.