Salt causes ion disequilibrium-induced programmed cell death in yeast and plants.
Programmed cell death (PCD) is a fundamental cellular process conserved in metazoans, plants and yeast. Evidence is presented that salt induces PCD in yeast and plants because of an ionic, rather than osmotic, etiology. In yeast, NaCl inhibited growth and caused a time-dependent reduction in viability that was preceded by DNA fragmentation. NaCl also induced the cytological hallmarks of lysigenous-type PCD, including nuclear fragmentation, vacuolation and lysis. The human anti-apoptotic protein Bcl-2 increased salt tolerance of wild-type yeast strain and calcineurin-deficient yeast mutant (cnb1Delta) that is defective for ion homeostasis, but had no effect on the NaCl or sorbitol sensitivity of the osmotic hypersensitive hog1Delta mutant -- results that further link PCD in the response to the ion disequilibrium under salt stress. Bcl-2 suppression of cnb1Delta salt sensitivity was ENA1 (P-type ATPase gene)-dependent, due in part to transcriptional activation. Salt-induced PCD (TUNEL staining and DNA laddering) in primary roots of both Arabidopsis thaliana wild type (Col-1 gl1) and sos1 (salt overly sensitive) mutant seedlings correlated positively with treatment lethality. Wild-type plants survived salt stress levels that were lethal to sos1 plants because secondary roots were produced from the shoot/root transition zone. PCD-mediated elimination of the primary root in response to salt shock appears to be an adaptive mechanism that facilitates the production of roots more able to cope with a saline environment. Both salt-sensitive mutants of yeast (cnb1Delta) and Arabidopsis (sos1) exhibit substantially more profound PCD symptoms, indicating that salt-induced PCD is mediated by ion disequilibrium.
Huh
Gyung-Hye
GH
Center for Plant Environmental Stress Physiology, Purdue University, 1165 Horticulture Building, West Lafayette, IN 47907-1165, USA.
Damsz
Barbara
B
Matsumoto
Tracie K
TK
Reddy
Muppala P
MP
Rus
Ana M
AM
Ibeas
José I
JI
Narasimhan
Meena L
ML
Bressan
Ray A
RA
Hasegawa
Paul M
PM
D000222:Adaptation, Physiological / Q000187:drug effects; D017209:Apoptosis / Q000187:drug effects*; D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development; D002467:Cell Nucleus / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006801:Humans; D017136:Ion Transport / Q000187:drug effects; D009154:Mutation; D063245:Plant Development; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D010944:Plants / Q000187:drug effects*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000502:physiology; D012965:Sodium Chloride / Q000494:pharmacology*; D013997:Time Factors; D014617:Vacuoles / Q000187:drug effects; D015003:Yeasts / Q000187:drug effects* / Q000254:growth & development
D019253:Proto-Oncogene Proteins c-bcl-2; D012965:Sodium Chloride