Abstract:
The fungal pathogen Cercospora zeina causes Grey leaf spot (GLS), a devastating
yield-limiting foliar disease of maize. GLS negatively impacts food security,
especially in sub-Saharan Africa where maize is a staple food source. In this
study the genomic DNA of C. zeina was sequenced using next-generation
sequencing, and the genome assembled to a 95.4% completeness based on the
presence of core genes. The functionality of the genome was confirmed by
transcriptome sequencing data mapping to the genome. Phylogenetics analysis
confirmed the genome to cluster with other C. zeina isolates. The functional
elements and gene regions were predicted using the MAKER genome annotation
pipeline. The predicted proteins were compared with the closely related species
Cercospora zeae-maydis, Cercospora beticola and Cercospora berteroae.
Functional annotation of proteins of specific classes were performed to identify
differences in secreted proteins, carbohydrate-active enzymes, lipases, proteases
and components of secondary metabolite biosynthesis clusters. The synteny of
the genes in the cercosporin toxin biosynthesis cluster was also confirmed in all
four species. To enhance the accuracy of the phylogenetic classification of
Cercospora species the orthologous relationship between proteins of a number of
Dothideomycete species were predicted. The single-copy orthologs specific to
the Cercospora genus were analyzed for phylogenetic information content, and
eight genes selected for primer design in regions of protein identity. Primers for
four genes were synthesized and tested for specificity during amplification of C.
zeina and C. zeae-maydis genomic DNA. Degenerate primer pairs for two genes
were selected for further analysis, due to sequencing confirming the correct
identity of the amplification products.
