A Novel Sterol Regulatory Element-Binding Protein Gene (sreA) Identified in Penicillium digitatum Is Required for Prochloraz Resistance, Full Virulence and erg11 (cyp51) Regulation

Abstract

Penicillium digitatum is the most destructive postharvest pathogen of citrus fruits, causing fruit decay and economic loss. Additionally, control of the disease is further complicated by the emergence of drug-resistant strains due to the extensive use of triazole antifungal drugs. In this work, an orthologus gene encoding a putative sterol regulatory element-binding protein (SREBP) was identified in the genome of P. digitatum and named sreA. The putative SreA protein contains a conserved domain of unknown function (DUF2014) at its carboxyl terminus and a helix-loop-helix (HLH) leucine zipper DNA binding domain at its amino terminus, domains that are functionally associated with SREBP transcription factors. The deletion of sreA (ΔsreA) in a prochloraz-resistant strain (PdHS-F6) by Agrobacterium tumefaciens-mediated transformation led to increased susceptibility to prochloraz and a significantly lower EC50 value compared with the HS-F6 wild-type or complementation strain (COsreA). A virulence assay showed that the ΔsreA strain was defective in virulence towards citrus fruits, while the complementation of sreA could restore the virulence to a large extent. Further analysis by quantitative real-time PCR demonstrated that prochloraz-induced expression of cyp51A and cyp51B in PdHS-F6 was completely abolished in the ΔsreA strain. These results demonstrate that sreA is a critical transcription factor gene required for prochloraz resistance and full virulence in P. digitatum and is involved in the regulation of cyp51 expression.

RNA-sequencing of Cercospora beticola DMI-sensitive and -resistant isolates after treatment with tetraconazole identifies common and contrasting pathway induction

“…Active SREBP turns on the expression of sterol synthesis enzymes and other oxygen-dependent proteins (Blatzer et al, 2011;Choi et al, 2015). Recently, Liu et al (2015) identified a novel SREBP gene (sreA) that was required for DMI-resistance and Cyp51 expression in Penicillium digitatum. In our study, we also identified a gene encoding SREBP induced along with ergosterol biosynthesis genes in both strains (Table 1), perhaps suggesting that oxygen is limiting and/or ergosterol deficiency is sensed in C. beticola cells upon DMI exposure.…”

The genetic architecture of emerging fungicide resistance in populations of a global wheat pathogen

“…HLH-domain proteins 351 constitute a large family of proteins acting as gene expression regulators(Massari & Murre 352 2000). Some members of this family were shown to boost drug resistance gene expression in 353 human tumors(Cheung 2004;Vandeputte et al 2002) and plant pathogens(Liu et al 2015). 354…”

Paralogous Cyp51s mediate the differential sensitivity of Fusarium oxysporum to sterol demethylation inhibitors

“…However, prochloraz can also inhibit activities of other CYP enzymes, including cytochrome P450 c17α‐hydroxylase/17, 20‐lyase (CYP17) and aromatase (CYP19) . In P. digitatum , deletion of sreA , a novel sterol regulatory element‐binding protein gene led to increased susceptibility to prochloraz, and prochloraz‐induced expression of cyp51A and cyp51B in P. digitatum was completely abolished in the ΔsreA strain . Thus, prochloraz could inhibit other CYPs and the induction of FoCYP51 expression by prochloraz might not be its function but a mechanism of resistance.…”