The Putative C 2 H 2 Transcription Factor VadH Governs Development, Osmotic Stress Response, and Sterigmatocystin Production in Aspergillus nidulans .

The VosA-VelB hetero-dimeric complex plays a pivotal role in regulating development and secondary metabolism in Aspergillus nidulans . In this work, we characterize a new VosA/VelB-activated gene called vadH , which is predicted to encode a 457-amino acid length protein containing four adjacent C 2 H 2 zinc-finger domains. Mutational inactivation of vosA or velB led to reduced mRNA levels of vadH throughout the lifecycle, suggesting that VosA and VelB have a positive regulatory effect on the expression of vadH . The deletion of vadH resulted in decreased asexual development (conidiation) but elevated production of sexual fruiting bodies (cleistothecia), indicating that VadH balances asexual and sexual development in A. nidulans . Moreover, the vadH deletion mutant exhibited elevated susceptibility to hyperosmotic stress compared to wild type and showed elevated production of the mycotoxin sterigmatocystin (ST). Genome-wide expression analyses employing RNA-Seq have revealed that VadH is likely involved in regulating more genes and biological pathways in the developmental stages than those in the vegetative growth stage. The brlA , abaA , and wetA genes of the central regulatory pathway for conidiation are downregulated significantly in the vadH null mutant during asexual development. VadH also participates in regulating the genes, mat2 , ppgA and lsdA , etc., related to sexual development, and some of the genes in the ST biosynthetic gene cluster. In summary, VadH is a putative transcription factor with four C 2 H 2 finger domains and is involved in regulating asexual/sexual development, osmotic stress response, and ST production in A. nidulans .