Abstract:
Elsinoë species are phytopathogenic fungi that cause serious scab diseases on economically important plants. The
disease symptoms arise from the effects of a group of phytotoxins known as elsinochromes, produced via a type-I
polyketide synthase (PKS) biosynthetic pathway. The elsinochrome gene cluster was first annotated in Elsinoë fawcettii
where the main type-I PKS gene was characterized as EfPKS1. A later study showed that this gene and the associated
cluster had not been correctly annotated, and that EfPKS1 was actually the anchor gene of the melanin biosynthetic
pathway. A new type-I PKS gene EfETB1 associated with elsinochrome production was also identified. The aim of this
study was to identify all type-I PKS genes in the genomes of seven Elsinoë species with the goal of independently verifying the PKS containing clusters for both melanin and elsinochrome production. A total of six type-I PKS classes were
identified, although there was variation between the species in the number and type of classes present. Genes similar
to the E. fawcettii EfPKS1 and EfETB1 type-I PKS genes were associated with melanin and elsinochrome production
respectively in all species. The complete melanin and elsinochrome PKS containing clusters were subsequently annotated in all the species with high levels of synteny across Elsinoë species. This study provides a genus-level overview
of type-I PKS distribution in Elsinoë species, including an additional line of support for the annotation of the melanin
and elsinochrome PKS containing clusters in these important plant pathogens.
