Exploring the potential of a rice NLR pair to engineer novel effector recognition specificities

Zdrzalek, Rafal (2021) Exploring the potential of a rice NLR pair to engineer novel effector recognition specificities. Doctoral thesis, University of East Anglia.

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Plants suffer from various diseases, which cause significant yield losses in crops annually. Pathogens
secrete effectors that interact with host targets and manipulate plant metabolism to promote the
infection. Translocated effectors can be perceived by plant immune receptors termed NLRs
(nucleotide-binding, leucine-rich repeat), restricting pathogen spread.
The rice NLR pair Pik-1/Pik-2 confers resistance to the fungal pathogen Magnaporthe oryzae by
perceiving variants of the AVR-Pik effector. This recognition is mediated via direct interaction
between AVR-Pik and an integrated HMA (heavy metal associated) domain within Pik-1.
In this work, I predominantly used biochemical and structural approaches to characterise several
aspects of rice/M. oryzae interactions. I investigated the working model of the Pikp-1/Pikp-2 pair
and demonstrated they function via a finely tuned cooperation that requires all domains of both
NLRs for function. Moreover, I showed both NLRs require their intact P-loop and MHD-like motifs,
and they can associate, before and after the perception of the AVR-PikD effector.
I also investigated the interaction between M. oryzae effectors from the PWL family, and their
potential target OsHIPP43 (rice HMA-containing isoprenylated plant protein 43). I demonstrated
that PWL effectors bind OsHIPP43 with micro to nanomolar affinity. I generated the chimeric
receptor Pikm-1OsHIPP43 and showed that it can perceive all tested PWL effectors in a transient
expression system. Additionally, I determined the crystal structure of the PWL2/OsHIPP43 complex.
This structure revealed that PWL2 belongs to the MAX effector superfamily. I demonstrated the
binding between PWL2 and OsHIPP43 cannot be easily compromised, which has implications for
engineering disease resistance.
Finally, I showed that the recently identified rice blast effector AVR-Pias represents a new structural
class of M. oryzae effector.
These findings can inform future rational design of NLRs with novel recognition specificities. In turn,
this can help provide continuous new solutions for tackling ever-evolving plant pathogens

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Jackie Webb
Date Deposited: 29 Apr 2022 13:31
Last Modified: 29 Apr 2022 13:35
URI: https://ueaeprints.uea.ac.uk/id/eprint/84859

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