Natural and CRISPR-induced genetic variation for plant immunity

Castel, Baptiste (2019) Natural and CRISPR-induced genetic variation for plant immunity. Doctoral thesis, University of East Anglia.

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Our understanding of the genetic basis of a trait primarily relies on analysing heritable phenotypic diversity.

For instance, different accessions of Arabidopsis thaliana (Arabidopsis) can either be resistant or susceptible to a given strain of Albugo candida, an oomycete that causes the white rust disease. The virulent Albugo candida race Exeter1 (AcEx1) can grow on most Arabidopsis accessions. Using the resistant Arabidopsis Oy-0, I mapped and cloned the gene responsible for AcEx1 resistance: White Rust Resistance 4A (WRR4A). Arabidopsis Col-0 also contains WRR4A but does not resist AcEx1. I found that WRR4ACol-0 has an early stop codon, which is responsible for the recognition specificity of some effector candidates from Albugo candida. This example illustrates how natural diversity can be used to identify Resistance-genes and reveal components of the plant immune system.

However, natural diversity is not always available. Clustered and regularly interspaces short palindromic repeats (CRISPR) from bacterial genomes defines an immune system, re-invented for genome editing. I optimized a CRISPR-Cas9 method to generate null alleles in Arabidopsis. Using this method, I produced a double mutant of two immunity-related gene candidates that are in tandem in the genome: AtNRG1A and AtNRG1B. I confirmed the 7-year-old hypothesis that NRG1A and NRG1B are redundantly required for signalling downstream of multiple Resistance-genes, mainly from the TIR-NLR immune receptor family. So far very few genes required for immunity upon Resistance-protein activation were defined. This second example illustrates that CRISPR can be used to generate variation to unravel redundant genetic pathways.

The widespread adoption of CRISPR tools is likely to lead to a better understanding of the plant immune system. Ultimately, it will result in solutions to deploy genetics-based resistance to protect our crops from disease, reducing the need for chemicals.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Users 9280 not found.
Date Deposited: 18 Jun 2019 09:52
Last Modified: 18 Jun 2019 09:52


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