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UBC Theses and Dissertations

Functional analysis of a plant metacaspase in negative regulation of innate immunity Xu, Fan


Programmed cell death (PCD) plays a central role in innate immune responses in plants. Plant metacaspases are distant relatives of animal caspases which have previously been shown to play important roles in regulating PCD. The Arabidopsis thaliana genome encodes three type I and six type II metacaspases (MCs). In this study, we showed that Arabidopsis type I metacaspase MC2 functions as a negative regulator of plant immunity. A loss-of-function mutant of MC2 exhibits dwarf morphology, constitutively activated defense responses including enhanced resistance to virulent pathogens and constitutive defence marker PATHOGENESIS RELATED (PR) gene expression. On the other hand, overexpression of MC2 leads to enhanced disease susceptibility. The autoimmune phenotype of mc2 is dependent on the adaptor receptor-like kinases (RLKs) BAK1/BKK1 and SOBIR1, suggesting that MC2 functions upstream of these RLKs to negatively regulate plant immunity.

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