BBB : Vol. 70 (2006) , No. 3 pp.583-590

Biochemical and Molecular Analyses of Gibberellin Biosynthesis in Fungi

1) Division of Agriscience and Bioscience, Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology (TUAT)

The plant hormone, gibberellin (GA), regulates plant growth and development. It was first isolated as a superelongation-promoting diterpenoid from the fungus, Gibberella fujikuroi. G. fujikuroi uses different GA biosynthetic intermediates from those in plants to produce GA₃. Another class of GA-producing fungus, Phaeosphaeria sp. L487, synthesizes GA₁ by using the same intermediates as those in plants. A molecular analysis of GA biosynthesis in Phaeosphaeria sp. has revealed that diterpene cyclase and cytochrome P450 monooxygenases were involved in the plant-like biosynthesis of GA₁. Fungal ent-kaurene synthase is a bifunctional cyclase. Subsequent oxidation steps are catalyzed by P450s, leading to biologically active GA₁. GA biosynthesis in plants is divided into three steps involving soluble enzymes and membrane-bound cytochrome P450. The activation of plant GAs is catalyzed by soluble 2-oxoglutarate-dependent dioxygenases, which is in contrast to the catalysis of fungal GA biosynthesis. This difference suggests that the origin of fungal GA biosynthesis is evolutionally independent of that in plants.

Key words:

biosynthesis; gene cluster; Gibberella fujikuroi; Phaeosphaeria sp. L487; terpenoid