brlA is necessary and sufficient to direct conidiophore development in Aspergillus nidulans

Abstract

The brlA gene of A. nidulans mediates the developmental switch from the indeterminate, apical growth pattern of vegetative cells to the budding growth pattern of conidiophores. brlA encodes a 432 amino acid polypeptide containing two directly repeated motifs resembling the Zn(II) coordination sites first recognized in Xenopus TFIIIA. Misscheduled expression of brlA in vegetative cells results in transcriptional activation of developmentally regulated genes, cessation of unidirectional hyphal growth, initiation of cellular transformations resembling those that occur during normal conidiophore development, and production of viable conidiospores. We propose that BRLA is a nucleic acid-binding protein whose expression in vegetative cells is sufficient to induce sporulation through its role in regulating expression of conidiation-specific genes.