Programmed Cell Death Of Malus Hupehensis Roots Under Water And Salt Stress

In order to study plant root PCD(programmed cell death) and effect of mitochondrial changes on plant root PCD under environmental stress, 20% PEG6000, 5‰NaCl(v/v) and exogenous hydrogen peroxide were used to simulate stress, and the material used in our experiments was one year seedling plant roots of Malus Hupehensis. Agrose electrophoresis, TUNEL(terminal TDT-mediated d-UTP-digoxigenin nick end labeling, TUNEL)method, AO (acridine orange) staining method, caspase3/7 activity determination and FCM (flow cytometry, FCM) technique were used to assay plant root PCD after being treated by 20% PEG6000, 5‰NaCl and exogenous hydrogen peroxide. And the effect of calcium on the mitochondrial changes and cell death during root PCD was also investigated. The results as follow:In this experiment, the induction of PCD by 20% PEG6000 or 5‰NaCl-treating was detected in Malus Hupehensis roots, for there had more positive reactions in TUNEL analysis than control indicate that DNA fragmentation with 3'-OH appeared in root cells and caspase3/7 activity increased sharply in the period of root programmed cell death. Further more, mitochondrial permeability transition (MPT) increasing, mitochondrial transmembrane potential(△?m) reducing, H2O2 accumulating and cyt c releasing were examined during the process of root cell death, which were important regulators in animal PCD. From the results, we can see that the changes of those regulators in root cell death had relationship with each others. In condition, the difference between 20% PEG treatment and 5‰NaCl treatment in respect of O2˙ˉproduction rate and H2O2 accumulation was showed. O2˙ˉproduction rate and H2O2 accumulation increased in the mode of slowly - quickly during the period of 20% PEG-treating, which in the mode of decreasing– increasing during the time of 5‰NaCl treating.Exogenous hydrogen peroxide-induced cell death was employed to study mitochondria function involved in Malus Hupehensis root cell death. Both hydrogen peroxide-induced cell death and the increase of MPT were partly blocked by application of MPTP-inhibitor CsA. MPT, cyt c concentration and H2O2 accumulation altered within 20 minutes of exogenous hydrogen peroxide application while there were not accompanied by the...