Next generation genomics for improved disease resistance in bread wheat.

Marchal, Clemence (2019) Next generation genomics for improved disease resistance in bread wheat. Doctoral thesis, University of East Anglia.

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Crop diseases reduce wheat yields by ~25% globally and thus pose a major threat to global food security. Yellow (stripe) rust caused by Puccinia striiformis f. sp. tritici, is distributed worldwide and is currently the most globally damaging cereal rust. Despite over 80 designated yellow rust resistance genes (Yr) in wheat, few have been cloned.

Using mutational resistance gene enrichment sequencing (MutRenSeq) we successfully cloned three non-canonical BED domain containing Nucleotide-binding and Leucinerich Repeat proteins (BED-NLRs) in wheat that confer different resistance spectra to yellow rust: Yr7, Yr5 and YrSP. We showed that all three genes are genetically linked and Yr5 is distinct from Yr7, whereas YrSP is a truncated allele of Yr5 with 99.8% sequence identity. We demonstrated that a single amino-acid change in the BED domain of Yr7 was sufficient to lead to a loss of resistance. Additionally, Yr5 and YrSP BED domains are identical and there is only one amino-acid polymorphism between Yr7 and Yr5/YrSP BED domains. We thus hypothesized that recognition specificity is not solely governed by the BED domain.

Given the presence of integrated BED domains, we asked whether their mode of action would be similar to what was proposed in the ‘integrated decoy’ model. To test this hypothesis, we combined comparative genomics and neighbour-net analyses to determine whether BED domain from BED-NLRs are sequence-related to certain BEDdomains from other BED-containing proteins. Additionally, we set-up transient expression assays in Nicotiana benthamiana to investigate the ability of Yr7 and Yr7 variants to trigger cell-death in this heterologous system. Together these results provide novel insights into the mode of action of BED-NLRs in disease resistance in crops.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 19 Oct 2022 14:04
Last Modified: 30 Nov 2022 01:38


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