Abstract
The peanut leaf spot pathogen Passalora arachidicola (Mycosphaerella arachidis) is known to produce dothistromin, a mycotoxin related to aflatoxin. This is a feature shared with the pine needle pathogen Dothistroma septosporum (Mycosphaerella pini). Dothistromin biosynthesis in D. septosporum commences at an unusually early stage of growth in culture compared to most other fungal secondary metabolites, and the biosynthetic genes are arranged in fragmented groups, in contrast to aflatoxin gene clusters. Dothistromin biosynthetic genes were identified and studied in P. arachidicola to determine if the attributes described in D. septosporum are shared by another dothistromin-producing species within the Class Dothideomycetes. It was shown that dothistromin biosynthesis is very similar in the two species with regard to gene sequence and gene synteny. Functional complementation of D. septosporum mutants with P. arachidicola dothistromin genes was also possible. These similarities support a vertical mode of dothistromin gene transmission. P. arachidicola also produced dothistromin at an early growth stage in culture, suggesting that this type of regulation pattern may be relevant to the biological role of dothistromin.
Highlights
Many plant pathogenic fungi produce secondary metabolites such as mycotoxins and phytotoxins.The ability to produce a particular type of metabolite is usually confined to specific taxa, but the distribution of metabolite production within taxonomic groups is often ‘patchy’ [1]
Dothistromin genes were identified in the peanut pathogen P. arachidicola and two of them confirmed by heterologous complementation to be involved in dothistromin biosynthesis
D. septosporum is seen in other dothistromin-producing fungi and our results showed that
Summary
Many plant pathogenic fungi produce secondary metabolites such as mycotoxins and phytotoxins.The ability to produce a particular type of metabolite is usually confined to specific taxa, but the distribution of metabolite production within taxonomic groups is often ‘patchy’ [1]. Many plant pathogenic fungi produce secondary metabolites such as mycotoxins and phytotoxins. Some secondary metabolites have a role in disease. There are many examples of host-selective toxins (active only against specific susceptible host cultivars or species) that are virulence factors for disease [1,2]. In general, the role of non-host-selective toxins is not so clear [3]. Dothistromin is a non-host-selective toxin that is toxic to a broad range of cell types [4]. It is produced by several species with teleomorphs in the genus Mycosphaerella including the pine needle pathogens Dothistroma septosporum and Dothistroma pini, and the peanut leaf spot pathogen Passalora arachidicola
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