Omic characterisation of multi-component defences against the necrotrophic pathogen Pyrenophora tritici-repentis in wheat

Supplementary data for a paper submission. The abstract is below. 

·         Tan Spot disease is caused by the necrotrophic pathogen Pyrenophora tritici-repentis (Ptr) and poses a significant threat to global wheat production. Therefore, novel sources of resistance need to be identified, coupled with a fuller mechanistic understanding of host responses to Ptr.

·         Herein, we characterise the interaction between a ToxA-positive Ptr strain and parental wheat lines from a multiparent advanced generation intercross (MAGIC) population. Genotypes displaying moderate resistance (‘Robigus’) or susceptibility (‘Hereward’) to Ptr challenge were identified and characterised through histological, metabolomic, and transcriptomic approaches.

·         Histological investigations indicated the prominence of papilla-based defences in Robigus. Transcriptomic analyses could link this to the expression of barrier-related genes i.e. actin polymerisation, callose deposition, vesicle trafficking, and cellulose synthesis. Inhibiting actin polymerisation with cytochalasin E increased lesion numbers but did not augment lesion growth, suggesting the deployment of other defence mechanisms. These may be influenced by auxin, as its exogenous application exacerbated symptom development.

·         Transcriptomic and metabolomic analyses in Hereward following challenge with Ptr suggested shifts in primary metabolism, affecting glycolysis, the TCA cycle, and the γ-aminobutyric acid (GABA) shunt. Activation of salicylic acid (SA)-associated genes, including NPR1 and WRKY33, was specific to Hereward, and exogenous SA increased susceptibility to Ptr in both genotypes.

·         This study suggests barrier defences could be effective against Ptr as well as a lack of susceptibility factors like SA or the appropriate processing of IAA. These findings offer potential avenues for enhancing wheat resistance to Ptr.