Adenine deaminase is encoded by Tad1 and participates in copper accumulation in Trichoderma reesei

• A novel adenine deaminase gene was cloned from Trichoderma reesei.
• This gene participates in the adenine catabolism pathways.
• This gene also participates in the copper accumulation.

We cloned a novel Tad1 gene and demonstrated that this gene is closely involved in copper bioaccumulation in Trichoderma reesei. Tad1 gene encodes a 510 amino acids protein of the amidohydrolase superfamily which belongs to COG0402. We found that adenine was the most efficient substrate of Tad1 protein among the substrates used in this study. Gene function was also investigated by overexpression and RNA interference. Results showed that copper accumulation increased in mutant cells when Tad1 was overexpressed; by contrast, copper accumulation significantly decreased when Tad1 was inhibited. To investigate the function of Tad1 in copper bioaccumulation, we determined adenine, hypoxanthine, and xanthine concentrations by reversed phase HPLC. Tad1 overexpression induced a substantial production of xanthine, which functions in binding numerous copper ions and reducing copper concentration. We further compared the gene expression profile of AT01 with that of a wild-type T. reesei strain grown in a medium containing 1.0 mM Cu2+ by performing DNA microarray. Several upregulated genes in the mutant were associated with adenine or copper metabolism.