A novel polyketide synthase gene cluster in the plant pathogenic fungus <i>Pseudocercospora fijiensis</i>

Published on 2019-02-08T18:50:16Z (GMT) by
<div><p><i>Pseudocercospora fijiensis</i>, causal agent of black Sigatoka of banana, produces polyketide synthase (PKS) pathways shown to be important in disease development by related Dothideomycete fungi. Genome analysis of the <i>P</i>. <i>fijiensis PKS8-1</i> gene identified it as part of a gene cluster including genes encoding two transcription factors, a regulatory protein, a glyoxylase/beta-lactamase-like protein, an MFS transporter, a cytochrome P450, two aldo/keto reductases, a dehydrogenase, and a decarboxylase. Genome analysis of the related pathogens <i>Pseudocercospora musae</i>, <i>Pseudocercospora eumusae</i>, and <i>Pseudocercospora pini-densiflorae</i>, identified orthologous clusters containing a nearly identical combination of genes. Phylogenetic analysis of PKS8-1 identified homology to PKS proteins in the monodictyphenone and cladofulvin pathways in <i>Aspergillus nidulans</i> and <i>Cladosporium fulvum</i>, respectively. Analysis of clustered genes showed that the <i>PKS8-1</i> cluster shares genes for enzymes involved in the production of the emodin intermediate in the monodictyphenone and cladofulvin pathways, but differs in many genes, suggesting production of a different metabolic product. Time course analysis of gene expression in infected banana showed up-regulation of <i>PKS8-1</i> and four of eight clustered genes as early as 2 weeks post-inoculation and remaining high through 9 weeks. Overexpression of the pathway through constitutive expression of an <i>aflR-</i>like transcription factor gene in the cluster resulted in increased expression in culture of <i>PKS8-1</i> as well as the four clustered genes that are up-regulated in infected plants. No differences were seen in timing or severity of disease symptoms with the overexpression strains relative to controls, however gene expression analysis showed no difference in expression <i>in planta</i> by an overexpression strain relative to controls. Thus constitutive expression of the <i>aflR</i>-like gene is not sufficient to upregulate the pathway above normal expression <i>in planta</i>. Pathway expression during all phases of disease development and conservation of the pathway in related <i>Pseudocercospora</i> species support a role for this pathway in disease.</p></div>

Cite this collection

Noar, Roslyn D.; Thomas, Elizabeth; E. Daub, Margaret (2019): A novel polyketide synthase gene cluster in the plant pathogenic fungus Pseudocercospora fijiensis. PLOS ONE. Collection.