The polyamines spermine and spermidine inhibit or induce programmed cell death inArabidopsis thaliana in vitroandin vivoin a dose dependent manner

Abstract

AbstractPolyamines are ubiquitous biomolecules with a number of established functions in eukaryotic cells. In plant cells, polyamines have previously been linked to abiotic and biotic stress tolerance, as well as to the modulation of programmed cell death (PCD), with contrasting reports on their pro-PCD and pro-survival effects. Here, we used two well established platforms for the study of plant PCD;Arabidopsis thalianasuspension cultures cells and the root hair assay, to examine the roles of the polyamines spermine and spermidine in the regulation of PCD. We demonstrate that both polyamines can trigger PCD when applied exogenously at higher doses, whereas at lower concentrations they inhibit PCD induced by both biotic and abiotic stimuli. Furthermore, we show that concentrations of polyamines resulting in inhibition of PCD generated a transient ROS burst in our experimental system, and activated the expression of oxidative stress- and pathogen response-associated genes. Finally, we examined PCD responses in existingArabidopsispolyamine synthesis mutants, and identified a subtle PCD phenotype inArabidopsisseedlings deficient in thermo-spermine. The presented data show that polyamines can have a role in PCD regulation, however that role is dose-dependent and consequently they may act as either inhibitors, or inducers, of PCD inArabidopsis.