Investigating the role of phytohormones in Fusarium head blight and Fusarium root rot of Brachypodium distachyon

Haidoulis, John (2021) Investigating the role of phytohormones in Fusarium head blight and Fusarium root rot of Brachypodium distachyon. Doctoral thesis, University of East Anglia.

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Fusarium graminearum causes Fusarium head blight (FHB) and Fusarium root rot (FRR) in small-grain cereals. Phytohormones are reported to affect host resistance to FHB. However the role of phytohormones on resistance to FRR is unknown. Brachypodium distachyon is an effective model for investigating both FHB and FRR. The role of phytohormones in the interaction between B. distachyon and F. graminearum was investigated.

Phytohormone treatment prior to F. graminearum infection assays were performed on B. distachyon floral and root seedling tissues. Jasmonic acid (JA), ethylene, auxin, cytokinin, and 3-aminobutanoic acid (BABA) induced the most significant effects on both FHB and FRR resistance. Tissue-specific effects of phytohormones were observed as JA and ethylene increased resistance to FRR but susceptibility to FHB. Salicylic acid (SA) only induced negative effects on FRR resistance. Tissue-independent effects were also observed. Auxin increased resistance whereas cytokinin and BABA increased susceptibility to both diseases.

An RNA-seq transcriptome analysis revealed that expression of genes associated with five phytohormones: JA, ethylene, auxin, cytokinin, and abscisic acid (ABA) were overrepresented in response to FHB and FRR. Generally, JA and ethylene associated genes showed similar expression patterns between tissues whereas auxin, cytokinin, and ABA associated genes showed dissimilar expression patterns between FHB and FRR. A transcriptome analysis of F. graminearum effectors with the same infected material revealed elevated expression of both core tissue-independent genes and several tissue-dependent genes during infection.

Ethylene signalling has been associated with F. graminearum susceptibility in wheat and Arabidopsis thaliana. The ability of F. graminearum to produce ethylene was demonstrated and the biosynthetic pathway used was identified. A candidate ethylene biosynthetic gene was identified through RNA-seq analysis and was deleted via a split-marker deletion method. No change in ethylene production, growth, or virulence was observed for the deletion strains.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 13 Oct 2021 13:21
Last Modified: 13 Oct 2021 13:21

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