A Single Gene Transfer of Gibberellin Biosynthesis Gene Cluster Increases Gibberellin Production in a Fusarium Fujikuroi Strain with Gibberellin Low Producibility

Fusarium fujikuroi, the causative agent of bakanae disease in rice, produces many kinds of secondary metabolites. Recently, two phylogenetic subgroups (F and G groups) of Japanese F. fujikuroi have been identified and found to have differences in their gibberellin (GA) and fumonisin production. G‐group F. fujikuroi produces large amounts of GA, but is a fumonisin nonproducer. F‐group produces large amounts of fumonisin, but is a GA low or nonproducer. We investigated the cause of low GA production in the F‐group. Genetic mapping suggests that low GA production in the F‐group strain Gfc0825009 is due to a GA gene cluster for GA biosynthesis. Analysis of the nucleotide and amino acid sequences of the genes in the GA gene cluster showed >98.4% homology between the F‐group strain Gfc0825009 and the G‐group strain Gfc0801001. Following a 7‐day culture under low nitrogen conditions, we found that expression of P450‐1, P450‐4, and P450‐2 in the cluster increased in the G‐group strain and not in the F‐group strain. We hypothesized that complementation by GA genes in the G‐group strain would be required to increase GA production in the F‐group strain. However, we found that this occurred with a single gene complementation of DES, P450‐1, P450‐4, or P450‐2. Simultaneous increase in the expression of P450‐1, P450‐4, and P450‐2 were detected in the complementary transformants. Moreover, the same phenomenon was observed by reintegration of its own P450‐1. Our results suggest the presence of unknown regulatory mechanisms of the GA gene cluster in F. fujikuroi.