Transcriptional Regulation by the Velvet Protein VE-1 during Asexual Development in the Fungus Neurospora crassa

Asexual reproduction in fungi facilitates the dispersal and colonization of new substrates and, in pathogenic fungi, allows infection of plants and animals. The velvet complex is a fungus-specific protein complex that participates in the regulation of gene expression in response to environmental signals like light, as well as developmental processes, pathogenesis, and secondary metabolism. The velvet complex in the fungus Neurospora crassa is composed of three proteins, VE-1, VE-2, and LAE-1. Mutations in ve-1 or ve-2, but not in lae-1, led to shorter heights of aerial tissue, a mixture of aerial hyphae and developing macroconidia, and increased microconidiation when they were combined with mutations in the transcription factor gene fl. VE-2 and LAE-1 were detected during vegetative growth and conidiation, unlike VE-1, which was mostly observed in samples obtained from submerged vegetative hyphae. We propose that VE-1 is the limiting component of the velvet complex during conidiation and has a major role in the transcriptional regulation of conidiation. Characterization of the role of VE-1 during mycelial growth and asexual development (conidiation) by transcriptome sequencing (RNA-seq) experiments allowed the identification of a set of genes regulated by VE-1 that participate in the regulation of conidiation, most notably the transcription factor genes vib-1 and fl. We propose that VE-1 and VE-2 regulate the development of aerial tissue and the balance between macro- and microconidiation in coordination with FL and VIB-1.