Author ORCID Identifier

Date Available


Year of Publication


Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation


Agriculture, Food and Environment


Plant Pathology

First Advisor

Dr. Pradeep Kachroo


Systemic acquired resistance (SAR) is a broad-spectrum disease resistance induced upon local infections that provides protection against secondary infections. Earlier work has shown that SAR is regulated by two parallel pathways, one of which is regulated by salicylic acid (SA), and the other one involves pipecolic acid (Pip), nitric oxide (NO), reactive oxygen species (ROS), azelaic acid (AzA), and glycerol-3-phosphate (G3P). Pip acts upstream of NO, ROS, AzA, and G3P in the local leaves but the distal accumulation of Pip depends on the biosynthesis and transport of SA and G3P.

Normal induction of SAR also requires mitogen-activated protein kinase (MPK) 3, which was suggested to regulate Pip levels. However, the mpk3 plants accumulated normal levels of SA, Pip, ROS and AzA after pathogen infection. The mpk3 plants also accumulated normal levels of Pip-derivative N-hydroxy Pip (NHP). These results suggest that defective SAR in mpk3 was not associated with Pip or NHP levels. Notably, the mpk3 plants accumulated reduced levels of G3P and the AZELAIC ACID INDUCED 1 (AZI1) protein. MPK3 was required for the stability of AZI1 transcript and activation of MPK3 positively regulated G3P. MPK3 regulates Pip levels in a light-dependent manner.

Pip levels were negatively regulated by the WRKY70 transcription factor, and consequently, the mutant wrky70plants showed higher basal levels of SA, Pip, and NHP. The wrky70 mutation partially alleviated the increased disease susceptibility phenotype of wrky33 mutant and suppressed the autoimmunity phenotype of camta2/3 plants. Surprisingly, wrky70 plants showed compromised SAR, suggesting that WRKY70 positively regulates an SA/Pip-independent factor that was required for SAR. Consistent with this notion, exogenous applications of SA, or Pip were unable to confer SAR on wrky70 plants. In contrast, exogenous application of G3P conferred partial SAR on wrky70 plants, suggesting that WRKY70 regulates G3P-biosynthesis and/or -transport. The transport of G3P was regulated by Plasmodesmata Callose Binding proteins 1 and 3, which were also required for the transport of the mobile signal TAS3a.

Digital Object Identifier (DOI)

Funding Information

This study was supported by:

  • the Anatomy and functions of LTP interactomes and their relationship to small RNA signals in systemic acquired resistance, the National Science Foundation (IOS# 2131400) in 2022;
  • the Center For Agricultural And Life Sciences Metabolomics (CALM), United States Department of Agriculture grant (# 2021-70410-35295) in 2021;
  • Molecular trafficking of signals during plant defense in 2015;
  • and China Scholarship Council Scholarship in 2017.

Available for download on Thursday, November 27, 2025