Functional characterization of the manganese transporter smf2 homologue gene, PsMnt, of Phanerochaete sordida YK-624 via homologous overexpression

Abstract

A homologue gene of the yeast natural resistance–associated macrophage protein (Nramp) family transporter smf2 was identified in the white-rot fungus Phanerochaete sordida YK-624. Relative expression levels of the homologue, designated PsMnt, were roughly equivalent in cultures containing 0 to 1,000 μM Mn(II), a concentration nontoxic to the fungus. In the PsMnt-overexpressing mutant, cellular Mn accumulation and manganese peroxidase (MnP) activity increased significantly in 4-day cultures containing 10 μM MnSO₄. Compared with the wild-type strain, MnP activity in the overexpressing mutants was higher at lower Mn concentrations (specifically 10–15 times higher). These results suggest that PsMnt is a high-affinity Mn transporter involved in cellular Mn accumulation under Mn-deficient conditions. This is the first report of an smf2 homologue in wood rot fungi.