The molecular arms race between plants and aphids: host R genes
Author(s)
Hougaard, Katia Carol
Type
Thesis
Abstract
Plant resistance genes (R genes) confer host immunity through interaction between the R gene products and effectors from pests and pathogens. Certain Medicago truncatula genotypes have resistance to specific pea aphid (Acyrthosiphon pisum) biotypes associated with the RAP1 (Resistance to Acyrthosiphon pisum 1) quantitative trait locus (QTL). Two candidate R genes, RAP1A and RAP1B, are associated with the RAP1 QTL. Research focused on the structure and function of RAP1A and RAP1B, candidate R genes’ relationship with host resistance, host defence responses, and interaction of biotic and abiotic stress. These topics were investigated through molecular biology and plant physiology experiments, studies with live plants and aphids, and bioinformatics analyses using data from RNA sequencing. Transgenic hosts with RAP1A or RAP1B showed significant resistance to compared to susceptible host genotypes, but the transgenic resistance was weaker than native RAP1 resistance. The RAP1-associated host defence mechanism was studied via transcriptomic and physiological responses in resistant and susceptible near isogenic lines (NILs) following aphid infestation, along with studies on phytohormone and secondary metabolite accumulation. Resistant and susceptible NILs both showed increased salicylic acid and isoflavonoid accumulation in response to aphid infestation, indicating a possible necessary but not sufficient hosts response. Bioinformatics analyses indicated that hosts with RAP1-associated resistance may maintain homeostasis in successful defence responses. Combination infestations with virulent aphid biotypes and drought treatments were used to test the vulnerabilities of host resistance, indicating that the RAP1-associated resistance can be temporarily suppressed via biotic and abiotic stress. Future directions in this research include further testing of transgenic RAP1A and RAP1B in other plant species with the aim of producing aphid-resistant crops.
Version
Open Access
Date Issued
2024-12-22
Date Awarded
01/11/2025
License URL
Advisor
Turnbull, Colin
Sponsor
Biotechnology and Biological Sciences Research Council (Great Britain)
The British Society for Plant Pathology
Imperial College London
Publisher Department
Department of Life Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)