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|Title:||Flowering-time regulators and intercellular salicylic acid contribute to age-related resistance in Arabidopsis thaliana|
|Abstract:||Some plants become more resistant to pathogens as they age, a phenomenon known as Age-Related-Resistance (ARR). In this thesis, the Arabidopsis thaliana-Pseudomonas syringae pathosystem was used to explore: i) the association between ARR and the transition to flowering, and ii) the idea that salicylic acid (SA) acts directly on pathogens in the intercellular space during ARR. The ARR phenotypes of flowering-time mutants and wild-type plants induced to flower early by transient exposure to long days suggest that flowering is neither required nor sufficient for ARR, and is not the developmental cue for ARR. Two MADS-domain transcription factors were identified that appear to play distinct roles in the regulation of flowering time and ARR. Specifically, SVP (SHORT VEGETATIVE PHASE) is required for ARR and contributes to intercellular SA accumulation, a key aspect of ARR. Mutant and overexpression analyses suggest that the role of SVP during ARR is to repress SOC1 (SUPPRESSOR OF OVEREXPRESSION OF CO 1), which contributes negatively to ARR, upstream of intercellular SA accumulation. Assessing the in vitro antimicrobial activity of SA under biologically relevant conditions, and estimating the concentration of intercellular SA during ARR, provided convincing evidence that SA acts as an antimicrobial agent in the intercellular space during ARR. Moreover, the results of in vitro biofilm assays and biofilm visualization in the intercellular space suggest that SA also plays a role in reducing P. syringae biofilm formation during ARR. Lastly, I present evidence that intercellular SA also plays a role during pattern- and effector-triggered immunity in young plants. Altogether this work highlights the complex interplay between disease resistance and development, and reveals the potential for direct effects of SA on phytopathogens in vivo. This fundamental knowledge will be useful for the management of existing crops and the development of new disease-resistant varieties.|
|Appears in Collections:||Open Access Dissertations and Theses|
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