Loss of CRWN Nuclear Proteins Induces Cell Death and Salicylic Acid Defense Signaling.

Defects in the nuclear lamina of animal cell nuclei have dramatic effects on nuclear structure and gene expression as well as diverse physiological manifestations. We report that deficiencies in CROWDED NUCLEI (CRWN), which are candidate nuclear lamina proteins in Arabidopsis (), trigger widespread changes in transcript levels and whole-plant phenotypes, including dwarfing and spontaneous cell death lesions. These phenotypes are caused in part by ectopic induction of plant defense responses via the salicylic acid pathway. Loss of CRWN proteins induces the expression of the salicylic acid biosynthetic gene , which leads to spontaneous defense responses in and mutants, which are deficient in two of the four CRWN paralogs. The symptoms of ectopic defense response, including pathogenesis marker gene expression and cell death, increase in older double mutants. These age-dependent effects are postulated to reflect an increase in nuclear dysfunction or damage over time, a phenomenon reminiscent of aging effects seen in animal nuclei and in some human laminopathy patients.