Role of hydrogen peroxide in stress-induced programmed cell death during somatic embryogenesis in Fraxinus mandshurica
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We examined how reactive oxygen species, in the form of hydrogen peroxide (H2O2), affect osmotic stress–induced programmed cell death during somatic embryogenesis from cotyledon explants of Manchurian ash (Fraxinus mandshurica Rupr.). We found that substantial osmotic stress was essential for Manchurian ash somatic cells to obtain embryogenic competence. The explant cells displayed hallmarks of programmed cell death, chromatin condensation, and DNA fragmentation to oligonucleotides during somatic embryogenesis. Increasing concentrations of plant growth regulators and sucrose in the medium increased osmotic stress thereby inducing H2O2 accumulation in the explant cells. We found that H2O2 concentration was significantly decreased in explant cells when the induction medium was modified, i.e., when reducing the concentration of sucrose, which reduces the osmotic pressure of the medium, or by withdrawing plant growth regulators at mid-culture. These treatments also decreased the proportion of explant cells undergoing programmed cell death. Accordingly, a decreased rate of somatic embryo induction was observed. These results show that PCD occurred during tissue browning and death of some explant cells during somatic embryogenesis in F. mandshurica. The ROS contributed to PCD in abiotic stress stimulated F. mandshurica cells.
KeywordsManchurian ash Somatic embryos Programmed cell death Reactive oxygen species Osmotic stress
We are very grateful for our laboratory colleagues for constructive discussions and technical support.
Y. L and S. HL conceived and designed the study. Y. L and H. C collected plant materials and prepared SE samples for analysis osmotic stress-induced PCD and intracellular H2O2 concentration. W. C and L. HN analyzed the results for experiments on osmotic stress-induced PCD and intracellular H2O2 concentration. Y. L and Z. DY contributed to the writing of the manuscript and data analyses. L. YH revised the manuscript. All authors read and approved the final manuscript.
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