Quantification of Ultraviolet-B Stress-Induced Changes in Nuclear and Cellular Sizes of Tobacco Bright Yellow-2 Cells

Abstract

In higher plants, ultraviolet (UV)-B irradiation induces DNA damage and inhibits DNA replication, and this subsequently inhibits plant growth. However, the specific responses of plant cells to UV-B stress remain largely unknown. Previously, we found that low-doses of UV-B irradiation-induced morphological changes in cultured plant cells and nuclei, using an evaluation system with tobacco Bright Yellow-2 (BY-2) cells. In this study, we quantified the effects of UV-B stress on transgenic BY-2 cells, by visualizing the nuclei in living cells using a fluorescent protein marker. The UV-B irradiated cells and their nuclei were enlarged 1–4 days after irradiation. We also observed significant size changes in the nuclei and cells 1–2 days after irradiation, with rates of increase of 131.36 and 138.42%, respectively. The ratio of nuclear sizes in the UV-B–irradiated cells was similar to the ratio of nuclear sizes found in the S and G₂ phases of the cell cycle. We suggest that low-doses of UV-B induce moderate increases of the nuclei and cell volumes through cell cycle arrest.