Kinetic analysis of double-strand break rejoining reveals the DNA reparability of gamma-irradiated tobacco cultured cells.
The rejoining efficiency of double-strand breaks (DSBs) was quantified by a DNA fragment-size analysis in tobacco protoplasts and CHO-K1 cells following gamma-ray irradiation in order to compare DNA reparability of higher plants with mammals. Results showed that the DSB rejoining efficiency of tobacco protoplasts is dependent on the temperature of post-irradiation cultivation and that it reaches a maximum at 27 degrees C, which represents the most suitable temperature for protoplast cultivation. The DSB rejoining kinetics of tobacco protoplasts were well represented by a biphasic-exponential equation: half of initial-induced DSBs were rejoined for 1 h and the others were almost rejoined within 4 h. We found that the DSB rejoining kinetics of tobacco protoplasts at 27 degrees C are the same as those of CHO-K1 cells at 37 degrees C. These findings indicate that the DSB rejoining efficiency of tobacco protoplasts and CHO-K1 cells are comparable at their respective cell cultivation temperatures, suggesting that DSB rejoining efficiency is little responsible for the higher radiation-tolerance of tobacco protoplasts.
Yokota
Yuichiro
Y
Quantum Beam Science Directorate, Japan Atomic Energy Agency, Watanuki, Takasaki, Gunma, Japan. yokota.yuichiro@jaea.go.jp
Wada
Seiichi
S
Hase
Yoshihiro
Y
Funayama
Tomoo
T
Kobayashi
Yasuhiko
Y
Narumi
Issay
I
Tanaka
Atsushi
A
D000818:Animals; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D007700:Kinetics; D011836:Radiation Tolerance; D013696:Temperature; D013997:Time Factors; D014026:Nicotiana / Q000235:genetics* / Q000528:radiation effects*