Author ORCID Identifier

https://orcid.org/0000-0002-3133-9205

Year of Publication

2020

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Agriculture, Food and Environment

Department

Plant Pathology

First Advisor

Dr. Aardra Kachroo

Abstract

Systemic acquired resistance (SAR), initiated by a plant upon recognition of microbial effectors, involves the generation of mobile signals at the primary infection site, which translocate to and activate defense responses in distal tissues. Among the signals contributing to SAR include salicylic acid (SA), nitric oxide (NO), reactive oxygen species (ROS), glycerol-3-phosphate (G3P), and pipecolic acid (Pip). Our previous studies show there are two branches of SAR signaling pathways in Arabidopsis: one regulated by NO/ROS-G3P and the other by SA. Both NO/ROS-G3P and SA-mediated signaling branches function in parallel during SAR. To better understand the role of Pip in SAR and the molecular mechanisms underlying Pip-mediated signaling, I investigated relationship between Pip and other SAR signals. My results suggest that Pip-mediated SAR is dependent on the NO/ROS-G3P branch of the SAR pathway. This is supported by the results that exogenous Pip increases NO, ROS, and G3P, but not SA. Detailed characterization of Pip metabolism showed that Pip acts upstream of several known and unknown derivatives. I also investigated involvement of ascorbic acid biosynthetic enzymes and several ROS scavenging enzymes in SAR. Together, my results suggest that Pip- and ROS-metabolic pathways regulate key steps of SAR signaling in plants.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2020.212

Available for download on Thursday, May 20, 2021

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