Restoration of Gibberellin Production in Fusarium proliferatum by Functional Complementation of Enzymatic Blocks

Abstract

Nine biological species, or mating populations (MPs), denoted by letters A to I, and at least 29 anamorphic Fusarium species have been identified within the Gibberella fujikuroi species complex. Members of this species complex are the only species of the genus Fusarium that contain the gibberellin (GA) biosynthetic gene cluster or at least parts of it. However, the ability of fusaria to produce GAs is so far restricted to Fusarium fujikuroi, although at least six other MPs contain all the genes of the GA biosynthetic gene cluster. Members of Fusarium proliferatum, the closest related species, have lost the ability to produce GAs as a result of the accumulation of several mutations in the coding and 5 noncoding regions of genes P450-4 and P450-1, both encoding cytochrome P450 monooxygenases, resulting in metabolic blocks at the early stages of GA biosynthesis. In this study, we have determined additional enzymatic blocks at the first specific steps in the GA biosynthesis pathway of F. proliferatum: the synthesis of geranylgeranyl diphosphate and the synthesis of ent-kaurene. Complementation of these enzymatic blocks by transferring the corresponding genes from GA-producing F. fujikuroi to F. proliferatum resulted in the restoration of GA production. We discuss the reasons for Fusarium species outside the G. fujikuroi species complex having no GA biosynthetic genes, whereas species distantly related to Fusarium, e.g., Sphaceloma spp. and Phaeosphaeria spp., produce GAs.

Loss of Gibberellin Production in Fusarium verticillioides ( Gibberella fujikuroi MP-A) Is Due to a Deletion in the Gibberellic Acid Gene Cluster

“…This is only possible if all the necessary transcriptional regulators, which might act in addition to AreA, exist and are active in F. verticillioides. These results clearly corroborate our previous findings in F. proliferatum, where the general transcription regulator AreA and other yet-unknown GA-specific regulator(s) were found to be functional (34).…”

“…Despite the overall high degree of sequence identity of GA biosynthesis genes in these species, several mutations accumulated in the 5Ј noncoding (e.g., FpP450-1 and FpP450-4) or coding regions (e.g., Fpggs2 and Fpcps/ks) of GA genes in F. proliferatum strain D02945. Complementation of this nonproducing strain with the ggs2 and cps/ks genes from F. fujikuroi restored the ability to produce GAs, demonstrating that the mutations in these genes were the main reason for the loss of GA production (32,34). In contrast to these results, we recently isolated a GA-producing strain, F. proliferatum ET-1, from the roots of tropical orchids (56).…”

“…While we did not find any GA-nonproducing F. fujikuroi strain isolated from rice, almost all the other Fusarium species of the G. fujikuroi species complex with different host plants have lost the ability to produce GAs due to multiple mutations in some GA cluster genes (33). Other genes in these clusters still encode functional enzymes, as they were able to complement the corresponding mutants of F. fujikuroi and restore the GA biosynthesis capability (34).…”

“…(19) maintained these clusters and produce GAs. Even among the closely related species of the G. fujikuroi species complex, only some are still able to produce GAs, while the others have lost this ability due to mutations in the GA gene cluster and/or to losses of one or more genes (32,33,34). F. verticillioides is an example for both GA gene losses and mutations.…”

“…Thus, fumonisins are produced by F. proliferatum and F. fujikuroi, as well as by F. verticillioides (12,37,49,51), moniliformin by F. verticillioides, F. fujikuroi and F. thapsinum (25,38), and beauvericin by isolates of F. fujikuroi, F. proliferatum, and F. subglutinans (12,55). In contrast, the production of GAs, a group of plant hormones, is so far mainly restricted to F. fujikuroi (MP-C) and F. konzum (MP-I), although several species of the G. fujikuroi species complex contain the entire GA-biosynthetic gene cluster (32,33,34).…”