The Arabidopsis gene CAD1 controls programmed cell death in the plant immune system and encodes a protein containing a MACPF domain.

Abstract

To clarify the processes involved in plant immunity, we isolated and characterized a single recessive Arabidopsis mutant, cad1 (constitutively activated cell death 1), which shows a phenotype that mimics the lesions seen in the hypersensitive response (HR). This mutant shows spontaneously activated expression of pathogenesis-related (PR) genes, leading to a 32-fold increase in salicylic acid (SA), indicating that activated SA signaling leads to the HR in cad1.
Inoculation of cad1 mutant plants with Pseudomonas syringae pv tomato DC3000 shows that cad1 mutants show a defense activation phenotype. Cloning of CAD1 reveals that this gene encodes a protein containing a domain with significant homology to the MACPF (Membrane attack complex and perforin) domain of complement components and perforin that are involved in innate immunity in animals. Furthermore, genetic analysis showed that the CAD1 protein negatively controls the SA-mediated pathway of programmed cell death in plant immunity.