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UBC Theses and Dissertations

Using chemical genetics to discover regulators in plant immunity Huang, Shuai


Plants fend off pathogens by using Resistance (R) protein receptors to recognize pathogenic effectors. Classical genetic methods have been used to study R protein activation. However, the usage of classical genetics is limited by redundancy and lethality. To overcome these problems, I performed a high-throughput chemical genetics screen. I screened a chemical library containing 3,600 small-molecule compounds with known functions in animal systems. I identified one compound, 353D7, an NMDA (N-methyl-D-aspartate) subtype glutamate receptor antagonist in animals, that was able to completely suppress the autoimmune phenotypes of chs3-2D (chilling sensitive 3, 2D), including the arrested growth morphology and PR (pathogenesis related) gene expression. I also demonstrated that 353D7 suppressed the morphology of chs3-2D in a dosage dependent manner. In addition, 353D7 could partially suppress flg22‒induced reactive oxygen species production. In Arabidopsis, there are twenty glutamate-like receptors (GLR) ‒encoding genes that share high homology with the animal ionotropic glutamate receptors (iGluRs). Activation of NMDA receptors triggers ion fluxes including Ca²⁺ influx across the plasma membrane (PM). Cytosolic Ca²⁺ is one of the most ubiquitous secondary messengers mediating numerous biological processes including plant defense. We hypothesize that 353D7 probably perturbs plant GLR‒mediated Ca²⁺ influx. This work will potentially help us discover the longsought Ca²⁺ channels on the plasma membrane necessary for plant defense.

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