Plasmids used in this study.

<div><p>Plant pathogenic fungi provoke devastating agricultural losses and are difficult to control. How these organisms acquire micronutrients during growth in the host environment remains poorly understood. Here we show that efficient regulation of copper acquisition mechanisms is crucial for plant colonization and virulence in the soilborne ascomycete <i>Fusarium oxysporum</i>, the causal agent of vascular wilt disease in more than 150 different crops. Using a combination of RNA-seq and ChIP-seq, we establish a direct role of the transcriptional regulator Mac1 in activation of copper deficiency response genes, many of which are induced during plant infection. Loss of Mac1 impaired growth of <i>F</i>. <i>oxysporum</i> under low copper conditions and abolishes pathogenicity on tomato plants and on the invertebrate animal host <i>Galleria mellonella</i>. Importantly, overexpression of two Mac1 target genes encoding a copper reductase and a copper transporter was sufficient to restore virulence in the <i>mac1</i> mutant background. Our results establish a previously unrecognized role of copper reduction and uptake in fungal infection of plants and reveal new ways to protect crops from phytopathogens.</p></div>