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Poster

Session: Session 2 Presenting Authors at Posters (Odds)

P-241 - Cytokinins negatively regulate poplar defense against an obligate biotrophic pathogen

Wednesday, July 16, 2025
13:30 - 15:15  
Location: Confex Hall 3
Nutrient exchange & role of metabolites in plant-microbe interactions

    Presenting Author(s)

  • CU

    Chhana Ullah

    Postdoctoral researcher
    Department of Biochemistry, Max Planck Institute for Chemical Ecology
    Jena, Thuringen, Germany

    • Author(s)

  • AR

    Ahalya Rajendran

    Max Planck Institute for Chemical Ecology
    Jena, Thuringen, Germany

  • SS

    Sarrin Shahadat

    Max Planck Institute for Chemical Ecology
    Jena, Thuringen, Germany

  • MR

    Michael Reichelt

    Max Planck Institute for Chemical Ecology
    Jena, Thuringen, Germany

  • AH

    Almuth Hammerbacher

    University of Pretoria
    Pretoria, Gauteng, South Africa

  • JG

    Jonathan Gershenzon

    Director
    Max Planck Institute for Chemical Ecology
    Jena, Thuringen, Germany

Cytokinins (CKs), primarily known as plant growth regulators, play important roles in plant-microbe interactions. Studies on herbaceous plants suggest that CKs act as signaling molecules with dual functions in plant defense by either facilitating or suppressing pathogen infection. Whether and how CKs are involved in pathogen interactions with woody plants remain unknown. Here, we investigate CK biosynthesis, metabolism and functions in poplar trees (Populus spp.) during infection by the rust fungus Melampsora larici-populina, an obligate biotrophic pathogen. We found that concentrations of isoprenoid CKs increased rapidly in poplar leaves after rust inoculation but declined during the fungal proliferation and sporulation stages. In contrast, levels of topolins, rare types of aromatic CKs present in poplar, increased throughout rust infection. Poplar trees treated with both isoprenoid (trans-zeatin) and aromatic (ortho-topolin and meta-topolin) types of CKs enhanced rust colonization by reducing the accumulation of defense hormones (e.g., salicylic acid and jasmonates) and antimicrobial flavonoids. Interestingly, enhanced topolins in poplar leaves also increase amino acid levels, which might benefit the biotrophic rust fungus for essential nutrient acquisition. Our results suggest that CKs act as negative regulators in poplar defense against rust fungus by reducing antimicrobial flavonoids and their regulatory hormones, and increased accumulation of accessible nutrients.