UBC Theses and Dissertations

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UBC Theses and Dissertations

Regulation of SOBIR1 accumulation and defence activation in an autoimmune mutant by specific components of ER quality control. Qian, Zhang


Plants are sessile organisms that are surrounded by pathogens. To stay healthy, they need a complex and sensitive immune system. Specific pattern-recognition receptors (PRRs) localized on the plasma membrane can recognize conserved motifs from pathogens and transduce the signal into the cell to initiate defence responses. The receptor-like kinase BAK1-INTERACTING RECEPTOR-LIKE KINASE 1 (BIR1), functions as a negative regulator of plant immunity. bir1-1 exhibits spontaneous cell death and constitutive defence responses that are dependent on SUPPRESSOR OF BIR1,1 (SOBIR1) and PHYTOALEXIN DEFICIENT 4 (PAD4). Here I present the evidence that ER-quality control, a collective mechanism ensuring that only native proteins are produced by the secretary pathway, plays important roles in regulating defence responses in bir1-1. Five components in ER-quality control pathways, including CRT3, UGGT, STT3a, ERdj3b and SDF2, are all required for the immune responses in bir1-1. Western blot analysis showed that mutations in CRT3, ERdj3b and UGGT lead to reduced accumulation of SOBIR1 protein. The data suggest that ER-quality control plays an important role in the accumulation of SOBIR1 and is required for the defence responses in bir1-1.

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