Fungal pathogen uses defence substances to promote its own growth

In the process, the pathogen breaks down the host plant’s tryptamine-based defence substances and converts them into the growth hormone auxin, thereby specifically suppressing the plant’s immune response. The BOKU team – comprising fungal molecular biologists and researchers in the fields of analytical chemistry and metabolomics – which emerged from the FWF-funded Special Research Project SFB Fusarium, was able to demonstrate that plant tryptamine derivatives such as coumaroyl-tryptamine and feruloyl-tryptamine initially inhibit fungal growth following infection.

However, the fungus counteracts this with enzymes (amidohydrolases) that hydrolyse these defence substances. The fungus can then convert the released tryptamine into indole-acetaldehyde and subsequently into auxin (indoleacetic acid). Using this false signal, it suppresses the plant’s defence response. A mutant of the fungus in which all seven genes encoding Cu²⁺ amine oxidases had been deleted showed greatly reduced auxin production in planta and reduced virulence. By reintroducing one of the genes, the defect in the fungus’s spread within the ear was restored. These new findings provide plant breeders with valuable insights into new strategies for improving Fusarium resistance and reducing mycotoxin contamination in cereals.

Link of the publication: The Fungal Pathogen Fusarium graminearum Can Hydrolyse Tryptamine‐Derived Hydroxy‐Cinnamic Acid Amide Defence Compounds, and Generates Highly Increased Auxin Levels in Wheat via Copper Amine‐Oxidases

Image: BOKU University/Gerlinde Wiesenberger

Research contact
Gerhard Adam, Ao.Univ.-Prof.i.R. Dipl.-Ing. Dr.rer.nat.
BOKU University 
Institute of Microbial Genetics
Email: gerhard.adam@boku.ac.at
Telefon: +43 1 47654-94482