Genetics of Dothistromin Biosynthesis of Dothistroma septosporum: An Update

Abstract

Dothistroma needle blight is one of the most devastating fungal pine diseases worldwide. The disease is characterized by accumulation in pine needles of a red toxin, dothistromin, that is chemically related to aflatoxin (AF) and sterigmatocystin (ST). This review updates current knowledge of the genetics of dothistromin biosynthesis by the Dothistroma septosporum pathogen and highlights differences in gene organization and regulation that have been discovered between the dothistromin and AF/ST systems. Some previously reported genes are promoted or demoted as ‘dothistromin genes’ based on recent research. A new dothistromin gene, norB, is reported, and evidence of dothistromin gene homologs in other Dothideomycete fungi is presented. A hypothesis for the biological role of dothistromin is outlined. Finally, the impact that the availability of the D. septosporum genome sequence will have on dothistromin research is discussed.

The Genomes of the Fungal Plant Pathogens Cladosporium fulvum and Dothistroma septosporum Reveal Adaptation to Different Hosts and Lifestyles But Also Signatures of Common Ancestry

“…Some dothistromin biosynthetic genes were identified in D. septosporum but unexpectedly they were in several mini-clusters rather than in one co-regulated cluster of genes as reported for aflatoxin-producing species of Aspergillus [36], [37], [38]. The similarity of dothistromin to aflatoxin enabled predictions to be made about other D. septosporum genes involved in dothistromin production [39]; the complete set of dothistromin genes will help us understand the evolution of dothistromin and aflatoxin gene clusters.…”

Evolutionary Mechanisms Involved in Development of Fungal Secondary Metabolite Gene Clusters

“…16 These species share orthologous genes with the AF-producing fungi, although cluster organization is different and results in the production of unique metabolites. 15,17 The chemical structures for these compounds can be seen in Figure 18.1. …”

“…17 Surprisingly, DOTH genes are not tightly clustered but, instead, are dispersed in six sections across a 1.3 Mb chromosome in D. septosporum (de Wit, personal communication). Considerable rearrangement of gene order is evident between the ST and DOTH gene groups (Figures 18.2c and 18.2d) such that it is not possible to determine an ancestral gene order.…”

The veA gene of the pine needle pathogen Dothistroma septosporum regulates sporulation and secondary metabolism

“…Genes required for dothistromin biosynthesis appear to be orthologs of AF genes and a common biosynthetic pathway is proposed (Schwelm and Bradshaw, 2010;Shaw et al, 1978). However unlike AF genes, dothistromin genes are not tightly clustered, but are arranged in several mini-clusters on a 1.3 Mb chromosome (Bradshaw et al, 2006;Schwelm and Bradshaw, 2010). Furthermore, dothistromin is produced mainly during early exponential phase in culture, instead of during late exponential and stationary phases as is normally seen for secondary metabolites such as AF (Schwelm et al, 2008).…”

“…Genes required for dothistromin biosynthesis appear to be orthologs of AF genes and a common biosynthetic pathway is proposed (Schwelm and Bradshaw, 2010;Shaw et al, 1978). However unlike AF genes, dothistromin genes are not tightly clustered, but are arranged in several mini-clusters on a 1.3 Mb chromosome (Bradshaw et al, 2006;Schwelm and Bradshaw, 2010).…”