Disease symptoms of some phytopathogenic fungi are associated with changes in cytokinin (CK) levels. Here, we show that the CK profile of ergot-infected rye plants is also altered, although no pronounced changes occur in the expression of the host plant's CK biosynthesis genes. Instead, we demonstrate a clearly different mechanism: we report on the first fungal de novo CK biosynthesis genes, prove their functions and constitute a biosynthetic pathway. The ergot fungus Claviceps purpurea produces substantial quantities of CKs in culture and, like plants, expresses enzymes containing the isopentenyltransferase and lonely guy domains necessary for de novo isopentenyladenine production. Uniquely, two of these domains are combined in one bifunctional enzyme, CpIPT-LOG, depicting a novel and potent mechanism for CK production. The fungus also forms trans-zeatin, a reaction catalysed by a CK-specific cytochrome P450 monooxygenase, which is encoded by cpp450 forming a small cluster with cpipt-log. Deletion of cpipt-log and cpp450 did not affect virulence of the fungus, but Δcpp450 mutants exhibit a hyper-sporulating phenotype, implying that CKs are environmental factors influencing fungal development.

Centre of the Region Haná for Biotechnological and Agricultural Research Palacký University and Institute of Experimental Botany AS CR Šlechtitelů 11 78371 Olomouc Czech Republic

Institute of Plant Biology and Biotechnology Westfälische Wilhelms University Münster Schlossplatz 8 48143 Münster Germany

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Biochemical and Structural Aspects of Cytokinin Biosynthesis and Degradation in Bacteria

The Hulks and the Deadpools of the Cytokinin Universe: A Dual Strategy for Cytokinin Production, Translocation, and Signal Transduction

Role of Cytokinins for Interactions of Plants With Microbial Pathogens and Pest Insects

Manipulation of cytokinin level in the ergot fungus Claviceps purpurea emphasizes its contribution to virulence

Production and Role of Hormones During Interaction of Fusarium Species With Maize (Zea mays L.) Seedlings

Cytokinin Metabolism of Pathogenic Fungus Leptosphaeria maculans Involves Isopentenyltransferase, Adenosine Kinase and Cytokinin Oxidase/Dehydrogenase

Comparative "Omics" of the Fusarium fujikuroi Species Complex Highlights Differences in Genetic Potential and Metabolite Synthesis