Exploring the molecular basis of nonhost resistance in evolutionarily divergent plants

Jeong, Hyeonmin (2025) Exploring the molecular basis of nonhost resistance in evolutionarily divergent plants. Doctoral thesis, University of East Anglia.

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Abstract

Over more than 500 million years of coevolution, plants have continuously updated their immune systems to resist surrounding pathogens. Most potential pathogens fail to infect a given plant species, and this phenomenon is collectively termed nonhost resistance (NHR). NHR is supported by a diverse repertoire of biochemical, cellular, and molecular mechanisms that restrict non-adapted pathogens. Although these mechanisms have been extensively studied in angiosperms, their origins and evolutionary trajectories across land plants remain largely unexplored. In this thesis, I show that key components of the immune chaperone complex underlying NHR, RAR1 (REQUIRED FOR MLA12 RESISTANCE 1) and SGT1 (SUPPRESSOR OF G2 ALLELE OF SKP1), as well as their interaction, are conserved across streptophytes, with a notable exception in ferns. In leptosporangiate ferns, the RAR1–SGT1 binding interface has diverged while maintaining the protein–protein interaction. This molecular coevolution was facilitated by promiscuous SGT1 intermediates. My findings illustrate how conserved protein–protein interactions can be rewired without disrupting their essential functions. I further investigated chaperone-mediated NHR in the liverwort Marchantia polymorpha by testing rar1 mutants and wild-type plants with diverse strains of the oomycete phytopathogen Phytophthora. I identified candidate pathogens whose resistance depends on a functional immune chaperone complex, establishing M. polymorpha as a valuable system to discover resistance genes and elucidate the molecular basis of pathogenesis in understudied Phytophthora species. Finally, I examined transcriptomic responses of plants and pathogens across diverse interactions. These analyses revealed that both hosts and pathogens deploy core transcriptomic programs during infection, rather than relying on host- or pathogen-specific strategies. In conclusion, my work on NHR and host range using diverse non-seed plants highlights deeply conserved mechanisms underlying plant–pathogen interactions, while uncovering how immune systems diversify through the rewiring of conserved molecular components across land plants.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	18 May 2026 07:42
Last Modified:	18 May 2026 07:42
URI:	https://ueaeprints.uea.ac.uk/id/eprint/103049
DOI:

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