Programmed cell death is induced by hydrogen peroxide but not by excessive ionic stress of sodium chloride in the unicellular green algaChlamydomonas reinhardtiiстатья из журнала
Аннотация: Eukaryotic microalgae serve as indicators of environmental change when exposed to severe seasonal fluctuations. Several environmental stress conditions are known to produce reactive oxygen species in cellular compartments, resulting in oxidative damage and apoptosis. The study of cell death in higher plants and animals has revealed the existence of an active 'programmed cell death' (PCD) process and similarities between such processes suggest an evolutionary origin. A study was undertaken to examine the morphological, biochemical and molecular responses of the unicellular green alga Chlamydomonas reinhardtii after exposure to oxidative (10 mM H2O2) and osmotic (200 mM NaCl and 360 mM sorbitol) stress. Concentrations of H2O2 (2–50 mM), NaCl and sorbitol (100–800 mM) were negatively correlated with growth. Biochemical analyses showed an increase in intracellular H2O2 production (2.2-fold with H2O2 and ~1.2–1.4-fold with NaCl and sorbitol) and activities of some antioxidant enzymes [super oxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX)]. Alteration of mitochondrial membrane potential (MMP) was observed upon treatment with H2O2 and NaCl, but not with sorbitol, indicating that the ionic stress component of NaCl altered the MMP. In addition, H2O2 led to the activation of a caspase-3-like protein, increase in the cleavage of a poly(ADP) ribose polymerase-1 (PARP-1)-like enzyme and formation of DNA nicks and laddering. With NaCl and sorbitol, no caspase activation, nor oligonucleosomal DNA laddering was observed, indicating non-apoptotic death. However, genomic DNA of NaCl (800 mM)-stressed cells, but not those of sorbitol-treated cells showed complete shearing. We conclude that the ionic rather than the osmotic component of NaCl leads to necrosis. These results unequivocally suggest that the vegetative cells of C. reinhardtii respond differentially to various stress agents, leading to different death types in the same organism. Moreover, unlike most other organisms, when exposed to NaCl this alga does not undergo PCD.
Год издания: 2015
Издательство: Taylor & Francis
Источник: European Journal of Phycology
Ключевые слова: Aquatic Ecosystems and Phytoplankton Dynamics, Photosynthetic Processes and Mechanisms, Plant Stress Responses and Tolerance
Открытый доступ: closed
Том: 50
Выпуск: 4
Страницы: 422–438