Genetic analysis of innate immune receptor accumulation and function in plants Public Deposited

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  • March 20, 2019
  • He, Yijian
    • Affiliation: College of Arts and Sciences, Department of Biology
  • To detect pathogen attack and subsequently trigger defense responses, plants utilize immune receptors composed of a nucleotide binding site (NB) domain and a C-terminal leucine-rich repeat (LRR) domain. Proper regulations of NB-LRR protein stability and activity are critical for plant healthy. Three genes, RAR1, SGT1 and HSP90, were uncovered as key regulators of NB-LRR proteins. To further study the mechanism that regulates NB-LRRs, I performed a genetic screen in the model plant Arabidopsis thaliana to isolate rar1 suppressor (rsp) mutants which restore the loss of NB-LRR protein accumulation, and the consequent loss of NB-LRR function, that are the principal phenotypes of rar1 mutants. Here, I present two rsp alleles of hsp90.2 mutants identified in the rar1 suppressor screen. The hsp90.2rsp mutants suppress all known rar1 phenotypes including reduced NB-LRR protein accumulation and loss of NB-LRR-mediated resistance to pathogens. The positions of hsp90.2rsp mutations in HSP90 crystal structure suggest that RAR1 likely functions in destabilizing the lid-closed conformation of HSP90, and induce the lid- open conformation that is important for loading and/or affecting NB-LRR clients. In addition, I describe two rsp alleles of COI1 gene which encodes a well-characterized receptor of the phytohormone Jasmonic Acid (JA). It is widely accepted that COI1 is involved in JA signaling-dependent disease resistance. However, the new coi1rsp mutants affected NB-LRR accumulation in a pattern independent of the JA signaling pathway. This indicates that not all disease resistance effects of COI1 require JA signaling. Moreover, I observed the genetic interactions between COI1 and two NB-LRR regulators, SGT1b and HSP90. coi1rsp proteins are expected to regulate NB-LRR accumulation levels and function via SGT1b and HSP90.
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  • ... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Biology.
  • Dangl, Jeffery L.

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