The Zn(II)2Cys6 putative transcription factor is involved in the regulation of leucinostatin production and pathogenicity of the nematophagous fungus <i>Paecilomyces lilacinus</i>

Zn(II)2Cys6 transcription factor genes encode transcription regulators that manage the infection potential and production of secondary metabolites such as toxins in fungi. In this study, a gene named <i>rolP</i> that encodes a putative Zn(II)2Cys6 transcription factor regulating leucinostatin production in the filamentous fungus <i>Paecilomyces lilacinus</i> was characterized by a gene knockout approach. The deduced proprotein consists of 705 amino acids and is highly homologous to the Zn(II)2Cys6 transcription factor of the entomopathogenic fungus <i>Metarhizium brunneum</i>. Predictive analysis of the secondary structure of the proportion showed that it has two domains. <i>Paecilomyces lilacinus</i> can produce nematotoxins leucinostatins A and B. Deletion of <i>rolP</i> from the <i>P. lilacinus</i> wild-type strain Pl36-1 leads to the absence of leucinostatin A, while a large increase in the leucinostatin A level was achieved in the <i>rolP</i> overexpression strain Ov-Pl36-1. During the process of nematode infection, <i>rolP</i> showed high expression levels at 48–72 h and peaked at 48 h. Bioassay tests confirmed the requirement of <i>rolP</i> for leucinostatin production. However, the root-knot second-stage juvenile-toxicity was minimized to 35.3% in Δ<i>rolP</i>; toxicity was 97.2% with Ov-Pl36-1 compared with 68.4% with the wild type strain Pl36-1. Interestingly, neither knockout nor overexpression of the <i>rolP</i> gene affected the growth or sporulation of <i>P. lilacinus</i>. Additionally, fungal nutrition and acidic media might stimulate the <i>rolP</i> activity of the wild type strain against nematodes. These findings suggested that the <i>rolP</i> gene is required for the induction and production of leucinostatins and is considered a leucinostatin regulatory gene in <i>P. lilacinus</i>.