Novel evidence for apoptotic cell response and differential signals in chromatin condensation and DNA cleavage in victorin-treated oats

Yao, N Tada, Y Park, P Nakayashiki, H Tosa, Y Mayama, S

N. Yao et al., Novel evidence for apoptotic cell response and differential signals in chromatin condensation and DNA cleavage in victorin-treated oats, PLANT J, 28(1), 2001, pp. 13-26

45

INGLESE

Article

Plant Sciences","Animal & Plant Sciences

PLANT JOURNAL

0960-7412 → ACNP

28

1

2001

13 - 26

ISI

0960-7412(200110)28:1<13:NEFACR>2.0.ZU;2-L

Histological and cytological evidence of where and when apoptotic cells occ ur in Pc-2/Vb oat cells treated with victorin was obtained by observing DNA strand breaks at both light (LM) and electron microscope (EM) levels using TUNEL techniques. DNA from leaf segments that had been floated on victorin solution with the abaxial epidermis removed showed typical ladders on agar ose gels. Nuclear chromatin condensation, followed by cell collapse, starte d in the mesophyll cells closest to the victorin solution. LM-TUNEL was pos itive in the non-collapsed cells but not in the collapsed cells in the trea ted leaves. However, the EM-TUNEL assay was positive in the nuclei of the n on-collapsed as well as the collapsed cells where nuclear fragments dispers ed into the cytoplasm, and the immunogold density was much higher than that in the cells killed by a high concentration of H2O2, suggesting that the v ictorin-treated collapsed cells are in the last stage of apoptotic cell dea th. The immunogold labelling in the victorin-treated non-collapsed cells wa s restricted to condensed heterochromatin, indicating that chromatin conden sation is associated with DNA cleavage. Pharmacological studies indicated t hat proteases and nucleases may play a role in the apoptotic response. Howe ver, the EM-TUNEL assay indicated that EGTA co-incubated with victorin bloc ked DNA cleavage, but failed to prevent chromatin condensation. Moreover, p rotein kinases were involved in chromatin condensation, but did not affect DNA digestion, suggesting that chromatin condensation and DNA cleavage are differentially regulated in the death process in oats.