The NcZrg-17 gene of Neurospora crassa encodes a cation diffusion facilitator transporter required for vegetative development, tolerance to endoplasmic reticulum stress and cellulose degradation under low zinc conditions.

The Neurospora crassa gene NcZrg-17 encodes a membrane protein with homology to the cation diffusion facilitator (CDF) family of transporters. We analyzed the phenotypic and functional characteristics of ΔNcZrg-17 and the implications of these characteristics in vivo. The ΔNcZrg-17 mutant showed several phenotypes that are zinc suppressible such as reduced growth rate, short aerial hyphae, increased hyphal branching, early and enhanced conidiation and delayed conidial germination. Furthermore, the NcZrg-17 gene was found to be crucial for survival in the presence of endoplasmic reticulum (ER) stress inducing chemical agents. In addition, we found that ΔNcZrg-17 mutant is defective in protein secretion on cellulose media under low zinc conditions, pointing towards a physiological role for NcZrg-17 in N. crassa. A gradual and delayed transcriptional upregulation (~ threefold) of NcZrg-17 on exposure to low zinc suggests its role in adaptation to low zinc rather than zinc homeostasis. Together our findings support a function of NcZrg-17 in normal vegetative growth, tolerance to ER stress and degradation of cellulose under low zinc conditions in N. crassa.