Genetic Background of Variable Gibberellin Production in the Fusarium Fujikuroi Species Complex

The Fusarium fujikuroi species complex (FFSC) is a cosmopolitan fungal lineage with production of a broad spectrum of secondary metabolites including mycotoxins, pigments and plant hormones. The FFSC includes many important plant pathogens. Fusarium fujikuroi, a member of the FFSC, causes rice bakane disease and has been recognized as the exclusive gibberellin (GA) producer for a long time. However, other species such as Fusarium proliferatum, Fusarium sacchari and Fusarium konzum in the FFSC were also identified to produce GA in recent 20 years. GA biosynthesis is conferred by a gene cluster including 7 adjacent genes (GA gene cluster). Expression of the GA genes is activated under limited nitrogen conditions. GA lowor non-production in most FFSC species was revealed to attribute to a partial deletion of the GA gene cluster, malfunction or low expression of the GA genes although the cause has not been fully elucidated. It has been reported that transcriptional factors, signaling components, global regulators and histone modification are involved in regulation of the GA gene expression.