The Transcriptional Regulator Hbx1 Affects the Expression of Thousands of Genes in the Aflatoxin-Producing Fungus Aspergillus flavus

In filamentous fungi, homeobox proteins are conserved transcriptional regulators described to control conidiogenesis and fruiting body formation. Eight homeobox ( ) genes are found in the genome of the aflatoxin-producing ascomycete, While loss-of-function of seven of the eight genes had little to no effect on fungal growth and development, disruption of , resulted in aconidial colonies and lack of sclerotial production. Furthermore, the mutant was unable to produce aflatoxins B and B , cyclopiazonic acid and aflatrem. In the present study, transcriptome analysis revealed that has a broad effect on gene expression, and the effect of increases overtime, impacting more than five thousand protein-coding genes. Among the affected genes, those in the category of secondary metabolism (SM), followed by that of cellular transport, were the most affected. Specifically, regarding the effect of on SM, we found that genes in 44 SM gene clusters where upregulated while 49 were downregulated in the absence of , including genes in the SM clusters responsible for the synthesis of asparasone, piperazine and aflavarin, all known to be associated with sclerotia. In addition, our study revealed that affects the expression of other transcription factor genes involved in development, including the conidiation central regulatory pathway and genes.