Pathogen Interactions and Resistance Mechanisms in Elm Trees

Elm trees (Ulmus spp.) have endured repeated assaults by fungal pathogens, most notably those causing Dutch elm disease (DED). Infection typically initiates with bark beetle vectors introducing cerato-ulmin-producing Ophiostoma species into the xylem, where fungal hyphae obstruct water transport and trigger host defence responses. Resistance mechanisms include physical occlusion of vessels by tyloses, induction of pathogenesis-related proteins, and mobilisation of secondary metabolites regulated by salicylic acid and jasmonic acid signalling. Endophytic and epiphytic microbiota can modulate these responses, either priming defences or competing with pathogens. Recent advances in genomic and transcriptomic profiling have revealed complex gene networks underpinning both tolerance in selected cultivars and full resistance in experimental hybrids, offering new opportunities for breeding and biocontrol strategies.

Research from Nature Portfolio

One study demonstrated that in tolerant American elm saplings a concurrent surge in jasmonic acid accumulation and early expression of defence-related genes at 96 hours post-inoculation is pivotal to restricting Ophiostoma novo-ulmi progression. This work highlighted dynamic cross-talk between jasmonic and salicylic acid pathways and their influence on fungal cerato-ulmin transcripts. Another investigation compared bark and wood tissues in inoculated elm, revealing that the xylem exhibits stronger induction of defence genes while phloem produces higher levels of stress hormones. These findings underscore tissue-specific contributions to overall resistance and the importance of timing in hormonal signalling.

Pathogen Interactions and Resistance Mechanisms in Elm Trees publication trend

The graph below shows the total number of articles in pathogen interactions and resistance mechanisms in elm trees across all publications each year (not limited to Nature Index journals).

Technical terms

Xylem: Vascular tissue responsible for water transport within the tree.

Epiphyte: Organism that grows on the surface of a plant without extracting nutrients from it.

Endophyte: Microorganism living inside plant tissues, often conferring benefits such as enhanced stress tolerance.

Jasmonic acid (JA): Plant hormone that regulates defence responses against necrotrophic pathogens and insect herbivores.

Salicylic acid (SA): Plant hormone central to systemic acquired resistance and defence against biotrophic pathogens.

Tyloses: Outgrowths of parenchyma cells into xylem vessels that block pathogen spread.

Transcriptome: Complete set of RNA transcripts produced by the genome under specific conditions.

References

1. Vaccination of Elms against Dutch Elm Disease—Are the Associated Epiphytes and Endophytes Affected?. Journal of Fungi (2023).
2. Unraveling the transcriptional features and gene expression networks of pathogenic and saprotrophic Ophiostoma species during the infection of Ulmus americana. Microbiology Spectrum (2024).
3. Simultaneous induction of jasmonic acid and disease-responsive genes signifies tolerance of American elm to Dutch elm disease. Scientific Reports (2016).
4. Bark and wood tissues of American elm exhibit distinct responses to Dutch elm disease. Scientific Reports (2017).
5. Priming of Plant Defenses against Ophiostoma novo-ulmi by Elm (Ulmus minor Mill.) Fungal Endophytes. Journal of Fungi (2021).
6. Deciphering the Genome-Wide Transcriptomic Changes during Interactions of Resistant and Susceptible Genotypes of American Elm with Ophiostoma novo-ulmi. Journal of Fungi (2022).
7. Complexities underlying the breeding and deployment of Dutch elm disease resistant elms. New Forests (2021).