The <i>Aspergillus flavus rtfA</i> Gene Regulates Plant and Animal Pathogenesis and Secondary Metabolism.
<i>Aspergillus flavus</i> is an opportunistic fungal plant and human pathogen and a producer of mycotoxins, including aflatoxin B<sub>1</sub> (AFB<sub>1</sub>). As part of our ongoing studies to elucidate the biological functions of the <i>A. flavus</i><i>rtfA</i> gene, we examined its role in the pathogenicity of both plant and animal model systems. <i>rtfA</i> encodes a putative RNA polymerase II (Pol II) transcription elongation factor previously characterized in <i>Saccharomyces cerevisiae</i>, <i>Aspergillus nidulans</i>, and <i>Aspergillus fumigatus</i>, where it was shown to regulate several important cellular processes, including morphogenesis and secondary metabolism. In addition, an initial study in <i>A. flavus</i> indicated that <i>rtfA</i> also influences development and production of AFB<sub>1</sub>; however, its effect on virulence is unknown. The current study reveals that the <i>rtfA</i> gene is indispensable for normal pathogenicity in plants when using peanut seed as an infection model, as well as in animals, as shown in the <i>Galleria mellonella</i> infection model. Interestingly, <i>rtfA</i> positively regulates several processes known to be necessary for successful fungal invasion and colonization of host tissue, such as adhesion to surfaces, protease and lipase activity, cell wall composition and integrity, and tolerance to oxidative stress. In addition, metabolomic analysis revealed that <i>A. flavus</i><i>rtfA</i> affects the production of several secondary metabolites, including AFB<sub>1</sub>, aflatrem, leporins, aspirochlorine, ditryptophenaline, and aflavinines, supporting a role of <i>rtfA</i> as a global regulator of secondary metabolism. Heterologous complementation of an <i>A. flavus</i><i>rtfA</i> deletion strain with <i>rtfA</i> homologs from <i>A. nidulans</i> or <i>S. cerevisiae</i> fully rescued the wild-type phenotype, indicating that these <i>rtfA</i> homologs are functionally conserved among these three species.<b>IMPORTANCE</b> In this study, the epigenetic global regulator <i>rtfA</i>, which encodes a putative RNA-Pol II transcription elongation factor-like protein, was characterized in the mycotoxigenic and opportunistic pathogen <i>A. flavus</i> Specifically, its involvement in <i>A. flavus</i> pathogenesis in plant and animal models was studied. Here, we show that <i>rtfA</i> positively regulates <i>A. flavus</i> virulence in both models. Furthermore, <i>rtfA</i>-dependent effects on factors necessary for successful invasion and colonization of host tissue by <i>A. flavus</i> were also assessed. Our study indicates that <i>rtfA</i> plays a role in <i>A. flavus</i> adherence to surfaces, hydrolytic activity, normal cell wall formation, and response to oxidative stress. This study also revealed a profound effect of <i>rtfA</i> on the metabolome of <i>A. flavus</i>, including the production of potent mycotoxins.