Investigating the evolution and function of LWY effectors in Phytophthora pathogens

Li, Yufei (2025) Investigating the evolution and function of LWY effectors in Phytophthora pathogens. Doctoral thesis, University of East Anglia.

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Abstract

Successful colonization on hosts depends on pathogen secreted virulence proteins, termed effectors. For the devastating Phytophthora pathogens, many effectors are composed of tandem repeats of the (L)WY motif. Each (L)WY unit forms a conserved 3 or 5 α-helical bundle. Multiple units can be concatenated through a conserved linkage to form the WY1-(LWY)n architecture. Despite the structural conservation, the (L)WY units are sequence-wise variable, leading to the hypothesis that they may mediate diverse interactions with host molecules. Shuffling of these (L)WY units further promotes functional diversification. In this thesis, I examined the role of (L)WY tandem repeats in promoting effector evolution in Phytophthora.

I identified (L)WY-encoding sequences across five Phytophthora species, revealing 73-173 LWY effector genes per genome. 15%-63% of these LWY genes encode proteins lacking the N-terminal secretion Signal Peptide (SP), with a subset also missing the host-targeting RxLR motif. This suggests these variants may serve as a genetic reservoir for unit recombination or be secreted through non-canonical mechanisms. The LWY genes form multi-gene clusters, potentially facilitating recombination. I identified a recombination event in which two (L)WY effectors recombined to form a hybrid effector. Analysis of host targets revealed both shared and unique host interactors with the “parent” and hybrid effectors, demonstrating recombination as a mechanism that drives the evolution of novel virulence activity in (L)WY effectors.

I classified the (L)WY units based on their surface residues and identified specific (L)WY-LWY combinations as potential functional modules using a co-occurrence analysis. Selected LWY effectors that carry these modules were further characterized for host interactors in Nicotiana benthamiana using immunoprecipitation and mass-spectrometry. In addition to the known PP2A-interacting module, this analysis revealed additional modules that may recruit E2 ligases in the host.

This thesis provides important insights into the modularity-driven evolution of pathogen effectors and reveals novel virulence mechanisms in Phytophthora.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Kitty Laine
Date Deposited:	03 Jun 2025 10:58
Last Modified:	03 Jun 2025 10:58
URI:	https://ueaeprints.uea.ac.uk/id/eprint/99384
DOI:

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