Functional characterization of tzn1 and tzn2-zinc transporter genes in Neurospora crassa

Abstract

Previous work from our laboratory involved the description of the Neurospora metal transportome, which included seven hypothetical zinc transporters belonging to the ZIP family. The aim of the present study was to make a comparative functional evaluation of two hypothetical zinc transporters named tzn1 (NCU07621.3) and tzn2 (NCU11414.3). Phenotypic analysis of tzn1 and tzn2 mutants and a double mutant (tzn1tzn2) revealed that the deletion of tzn1 causes aconidiation and a greater defect in growth than the single deletion of tzn2. Supplementation with zinc restores growth but not conidiation in tzn1 and tzn1tzn2. TZN1 complemented a zinc-uptake-deficient Saccharomyces cerevisiae mutant (zrt1zrt2) in zinc-deficient conditions, while tzn2 restored growth upon supplementation with zinc (0.05 mM). Furthermore, the Deltatzn1 mutant was found to have severely reduced zinc content indicating that tzn1 functions as a key regulator of intracellular zinc levels in Neurospora crassa. Zinc uptake studies indicate tzn1 is a specific transporter of zinc, while tzn2 transports both zinc and cadmium. Quantitative RT-PCR showed up-regulation of tzn1 (128-fold) under zinc-depleted conditions and down-regulation (>1,000-fold) in zinc-replete conditions. The present study indicates that the zinc transport proteins encoded by tzn1 and tzn2 are members of the zinc uptake system regulated by zinc status in N. crassa.

The SlZRT1 Gene Encodes a Plasma Membrane-Located ZIP (Zrt-, Irt-Like Protein) Transporter in the Ectomycorrhizal Fungus Suillus luteus

“…A fast transcriptional response on limited environmental Zn concentrations is common for plasma membrane localized Zn transporters of the ZIP I subfamily. Induction of transcription in the absence of external Zn was reported previously for fungal ZIP I subfamily Zn importers which were identified in Ascomycota (ScZRT1 of Schizosaccharomyces pombe , ZrfA, ZrfB and ZrfC of Aspergillus fumigatus , Tzn1 and Tzn2 of Neurospora crassa , CaZRT1 and CaZRT2 of Candida albicans ) and in Basidiomycota (CgZIP1 and GgZIP2 of Cryptococcus gattii ) ( Dainty et al, 2008 ; Kiranmayi et al, 2009 ; Jung, 2015 ).…”

“…Among fungi, mechanisms involved in Zn homeostasis are mostly studied in S. cerevisiae. Transporters of the ZIP family were shown to be vital to prevent Zn deficiency in this species ( Eide, 2006 ) and several other fungi ( Kiranmayi et al, 2009 ; Jung, 2015 ). S. cerevisiae possess two plasma membrane localized Zn importers of the ZIP family (ScZRT1 and ScZRT2) and one tonoplast localized ZIP transporter (ScZRT3) for re-mobilization of vacuolar stored Zn.…”

Csr1/Zap1 Maintains Zinc Homeostasis and Influences Virulence in Candida dubliniensis but Is Not Coupled to Morphogenesis

“…The simultaneous deletion of two zinc transporter genes TZN1 and TZN2 in Neurospora crassa caused a growth defect under zinc depletion conditions, and this double mutant strain failed to exhibit conidiation ( 42 ). In this context, we tested production of chlamydospores on Staib and rice agar under chlamydospore-inducing conditions (see Fig.…”

Expression and functional characterisation of TNC, a high-affinity nickel transporter from Neurospora crassa

“…However, functional roles for the metal transporters with respect to their physiological relevance in various developmental stages of N. crassa remain largely unexplored. The first study in this direction was on the transitional zinc ion transporter gene tzn1, whose mutant demonstrated the aconidiation phenotype in N. crassa (Kiranmayi et al, 2009). Subsequently, role of the copper transporters has been established in the saprophytic conidial germination of N. crassa (Korripally et al, 2010).…”