Approaches towards disease resistance to filamentous pathogens

Giannakopoulou, Artemis (2015) Approaches towards disease resistance to filamentous pathogens. Doctoral thesis, University of East Anglia.

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Abstract

In the co-evolutionary arms race between plants and pathogens, plants have
developed a multifaceted armory consisting of diverse defence responses, such as
the production of antimicrobial compounds and the activation of immunity via specific
receptors. This work examines the use of the phytoalexin capsidiol and synthetic
NLR immune receptors as disease resistance approaches against oomycete and
fungal plant pathogens. The production of phytoalexins constitutes an important
aspect of plant defence. Capsidiol, a pepper phytoalexin, differentially inhibits the
growth of two Phytophthora species, the late-blight pathogen P. infestans and the
vegetable pathogen P. capsici. The differential effect of capsidiol towards these two
oomycetes was determined and quantified. I also monitored intraspecific variation
among various P. infestans isolates in their sensitivity towards capsidiol. Plant
defence machinery also involves intracellular immune receptors of the Nucleotidebinding
Leucine-rich Repeat-containing protein family (NLRs). NLRs typically
recognize pathogen effector proteins with avirulence activities, leading to a response
known as effector-triggered immunity (ETI). R3a and I2 are orthologous NLRs from
potato and tomato responding to effectors of P. infestans and the wilt fungus
Fusarium oxysporum f. sp. lycopersici, respectively. Yet, particular races of these
pathogens have evolved stealthy effectors that evade recognition by R3a and I2. I
assessed whether previously identified mutations in R3a, with expanded response
specificities to Phytophthora spp. effectors, can be transferred to I2 with similar
beneficial effects. I recovered I2 mutants with expanded response spectrum to
effectors from both P. infestans and F. oxysporum f. sp. lycopersici. Infection assays
in both transient and stable transgenic systems suggested this expanded response
correlates with resistance. I finally investigated whether the I2 locus is a determinant
of tomato resistance against P. infestans. Overall, these findings generate new
insights into the molecular interactions underlying plants response to pathogens, and
open up applied perspectives for sustainable crop disease resistance.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Users 2259 not found.
Date Deposited:	05 May 2016 10:40
Last Modified:	01 Mar 2017 01:38
URI:	https://ueaeprints.uea.ac.uk/id/eprint/58580
DOI:

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