Abstract
To clarify the processes involved in plant immunity, we have isolated and characterized Arabidopsis mutant, cad1 (constitutively activated cell death 1), which shows a phenotype that mimics the lesions seen in the hypersensitive response. This mutant shows spontaneously activated expression of pathogenesis-related genes, and leading to 32-fold increase in salicylic acid (SA). Inoculation of cad1 mutant plants with virulence pathogen shows that the cad1 mutation results in the restriction of bacterial growth. Cloning of CAD1 reveals that this gene encodes a protein containing a domain with significant homology to the MACPF domain of complement components and perforin proteins that are involved in innate immunity in animals. Furthermore, cell death is suppressed in transgenic cad1 plants expressing nahG (Plant Cell Physiol. 2005, 46: 902-912; Biosci. Biotechnol. Biochem. 2006, 70, 2042-2048). Molecular genetic studies on SA-mediated pathway of programmed cell death in the cad1 mutant will be reported.
