The velvet-activated putative C6 transcription factor VadZ regulates development and sterigmatocystin production in Aspergillus nidulans

Abstract

The NF-ƙB-type VosA–VelB velvet complex acts as a global regulator governing development and metabolism in fungi. One of the VosA-VelB-activated developmental (VAD) genes called vadZ is predicted to encode a 557-amino acid protein containing a highly conserved GAL4-type Zn(II)2Cys6 (or C6 zinc) binuclear cluster DNA-binding domain in Aspergillus nidulans. In this report, we characterize the function of the vadZ gene in controlling development and sterigmatocystin (ST) production in A. nidulans. To verify VosA–VelB mediated activation of vadZ, we checked relative mRNA levels of vadZ in wild-type (WT), ΔvosA, and ΔvelB mutant strains during vegetative, asexual, and sexual development phases. At the beginning of asexual development, the absence of vosA led to a 66.2-fold lowered vadZ mRNA levels, whereas ΔvelB resulted in a 3.6-fold decrease in vadZ mRNA levels. The deletion of vadZ resulted in significantly restricted colony growth coupled with reduced asexual development, but increased formation of sexual fruiting bodies called cleistothecia. In addition, nullifying vadZ caused elevated mRNA levels of the two key sexual developmental activators esdC and nsdD throughout the lifecycle. Moreover, the ΔvadZ mutant showed elevated production of ST and enhanced mRNA levels of ST biosynthetic genes. In summary, the putative C6 transcription factor VadZ promotes asexual development and suppresses the sexual development and the ST production in A. nidulans.