Date Available

5-7-2020

Year of Publication

2018

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Agriculture, Food and Environment

Department/School/Program

Plant Pathology

Advisor

Dr. Pradeep Kachroo

Abstract

Systemic acquired resistance (SAR) is a type of plant defense mechanism that is induced after a localized infection and confers broad-spectrum immunity against related or unrelated pathogens. During SAR, a number of chemical signals and proteins generated at the site of primary infection travel to the uninfected tissues and are thought to alert the distal sites against secondary infections. Glycerol-3-phosphate (G3P) is one of the chemical signals that play an important role in SAR. G3P is synthesized in the cytosol and chloroplasts via the enzymatic activities of G3P Dehydrogenase (G3Pdh) or Glycerol Kinase (GK). Interestingly, a mutation in three of the five G3Pdh isoforms or GK impairs SAR by lowering the pathogen induced G3P pool. This suggests that total cellular pool of G3P is critical for SAR. To determine factors contributing to G3P flux between various subcellular compartments I analyzed the role of putative G3P transporters in G3P flux and SAR. The Arabidopsis genome encodes five isoforms of G3P Permeases (G3Pp) and these transmembrane proteins are predicted to localize to plasma membrane, chloroplast or mitochondria. At least two G3Pp isoforms (G3Pp1 and G3Pp3) were able to complement the Escherichia coli mutant impaired in the uptake of G3P into the cytoplasm. Characterization of Arabidopsis G3Pp mutants showed that a mutation in G3Pp2, G3Pp3 and G3Pp4 compromised SAR but not local resistance. Furthermore, this SAR defect could only be complemented by exogenous application of G3P. The G3Pp mutants accumulated wild-type-like levels of G3P suggesting that the subcellular compartmentalization of G3P might contribute to the induction of SAR.

Digital Object Identifier (DOI)

https://doi.org/10.13023/ETD.2018.134

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