When your enemy becomes your friend: Evolution of the interaction between fungi and land plants

Plants live in close association with microbes, establishing interactions that range from beneficial to detrimental.

Molecular plant-microbe interactions have been extensively studied in flowering plants, whereas research in non-seed plant lineages has been hindered by the lack of pathosystems reflecting natural plant-microbe interactions.

My team and I identified the first example of a fungus that establishes opposite interactions with flowering and non-seed plants.

We discovered that the fungus Trichoderma, which promotes plant growth, defense, and stress tolerance in flowering plants, is pathogenic for other land plant lineages (non-vascular plants and ferns) indicating unexpected differences in land plant immunity and fungus behavior.

The overarching goal of our project FRIENEMIES is to decipher the molecular evolution of plant-microbe interactions from pathogenic to beneficial across land plants.

In FRIENEMIES, my team and I will characterize the molecular mechanisms involved in disease in non-seed plants using three genetically tractable non-seed model plants (two bryophytes and the C-fern) and a diversity panel of sequenced Trichoderma strains where we will identify fungal effectors, plant susceptibility and resistance genes and signaling pathways relevant for pathogenic interactions.

Combining omics, reverse genetics, natural variation, and phylogenetic analyses we will reveal the conservation of susceptibility/resistance mechanisms in other plant lineages and determine the emergence of mutualistic interactions between Trichoderma and land plants.

We envision that FRIENEMIES will describe fundamental differences in immunity across land plants, discover potentially novel and conserved molecular mechanisms mediating plant-microbe interactions, define their evolutionary trajectories, and reveal the key evolutionary switches associated with major innovations in land plants underlying the transition between susceptibility, resistance, and mutualism.