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The PacC transcription factor regulates pH-dependent fungal development and virulence in the barley pathogenic fungus Cochliobolus sativus

Yueqiang Leng: North Dakota State University

<div>Fungi can grow in a wide range of pH in nature. The ambient pH regulatory system that controls the expression of both acid and alkaline expressed genes have been identified in <em>Aspergillus</em> and other fungi. Among the genes involved in this system, <em>PacC</em>, a gene encoding the zinc-finger transcription factor, plays a central role. In this study, we identified and characterized a homologous gene (<em>CsPacC</em>) of <em>PacC</em> from <em>Cochliobolus sativus</em>, the causal agent of spot blotch on barley. The deletion of <em>CsPacC</em> resulted in poor vegetative growth at high pH (9.0), suggesting that <em>CsPacC</em> is involved in activation of the genes when grown under alkaline conditions. Conidial production increased in the wild type isolate when the pH values increased from 5 to 9; however, the<em> ΔCsPacC</em> mutant produced less conidia compared to the wild type under the same conditions. Real time quantitative PCR revealed that the expression of <em>CsPacC</em> was pH dependent. The relative expression of <em>CsPacC</em> was about four times more at pH 9.0 than at pH 5.0. The virulence of the<em> ΔCsPacC</em> mutant was significantly reduced compared to the wild type. Complementation of the mutant with the wild type <em>CsPacC</em> restored the phenotypes to the wild type. RNA-seq revealed differential expression patterns of some genes between wild type and the <em>ΔCsPacC</em> mutant under different pH conditions. These results indicated that <em>CsPacC</em> regulates transcription of alkaline expressed genes and also genes involved in virulence on barley.</div>