Functional genomics‐guided discovery of a light‐activated phytotoxin in the wheat pathogen Parastagonospora nodorum via pathway activation

Abstract

Parastagonospora nodorum is an important pathogen of wheat. The contribution of secondary metabolites to this pathosystem is poorly understood. A biosynthetic gene cluster (SNOG_08608-08616) has been shown to be upregulated during the late stage of P. nodorum wheat leaf infection. The gene cluster shares several homologues with the Cercospora nicotianae CTB gene cluster encoding the biosynthesis of cercosporin. Activation of the gene cluster by overexpression (OE) of the transcription factor gene (SNOG_08609) in P. nodorum resulted in the production of elsinochrome C, a perelyenequinone phytotoxin structurally similar to cercosporin. Heterologous expression of the polyketide synthase gene elcA from the gene cluster in Aspergillus nidulans resulted in the production of the polyketide precursor nortoralactone common to the cercosporin pathway. Elsinochrome C could be detected on wheat leaves infected with P. nodorum, but not in the elcA disruption mutant. The compound was shown to exhibit necrotic activity on wheat leaves in a light-dependent manner. Wheat seedling infection assays showed that ΔelcA exhibited reduced virulence compared with wild type, while infection by an OE strain overproducing elsinochrome C resulted in larger lesions on leaves. These data provided evidence that elsinochrome C contributes to the virulence of P. nodorum against wheat.

Heterologous biosynthesis of elsinochrome A sheds light on the formation of the photosensitive perylenequinone system

“…1). Our group recently identified the elc cluster from the wheat pathogen Parastagonospora nodorum for 3 , which has been shown to be important for its virulence 11…”

CRISPR-mediated activation of biosynthetic gene clusters for bioactive molecule discovery in filamentous fungi

“…The modular nature of the AMA1 vector set allowed rapid building, testing and exchange of the different CRISPRa components. For an initial proof-of-concept, we built as test target a fluorescent reporter fusing mCherry to Parastagonospora nodorum elcA promoter ( P elcA ), which belongs to a ‘silent’ polyketide synthase gene 26 , and delivered it encoded on a AMA1 vector.…”

Genome Sequencing and Analysis of the Hypocrellin-Producing Fungus Shiraia bambusicola S4201

“…the sources of HA substrates, and the genes marked with red on the right were upregulated in the transcriptome analysis we performed (Zhao et al, 2016). The proposed functions of the proteins encoded by the HA biosynthesis gene cluster are based on the biosynthesis studies of cercosporin (Newman and Townsend, 2016) and elsinochrome C (Chooi et al, 2017). The orange dotted lines represent the substrates for HA biosynthesis.…”

“…The HPLC results also proved that overexpression of zftf increases HA production. A hypothetical HA biosynthetic pathway has been proposed based on the latest studies on cercosporin (Newman and Townsend, 2016) and elsinochrome C (Chooi et al, 2017), but it still needs to be validated with additional experiments. Figure 8 is a hypothetical flow diagram showing the biosynthesis of HA from substrates to its release by cells, in which the pathways are annotated based on the KEGG database.…”