Response to UV-C radiation in topo I-deficient carrot cells with low ascorbate levels.
In animal cells, recent studies have emphasized the role played by DNA topoisomerase I (topo I) both as a cofactor of DNA repair complexes and/or as a damage sensor. All these functions are still unexplored in plant cells, where information concerning the relationships between DNA damage, PCD induction, and topo I are also limited. The main goal of this study was to investigate the possible responses activated in topo I-depleted plant cells under oxidative stress conditions which induce DNA damage. The carrot (Daucus carota L.) AT1-beta/22 cell line analysed in this study (characterized by an antisense-mediated reduction of top1beta gene expression of approximately 46% in association with a low ascorbate content) was more sensitive to UV-C radiation than the control line, showing consistent cell death and high levels of 8-oxo-dG accumulation. The topo I-depleted cells were also highly susceptible to the cross-linking agent mitomycin C. The death response was associated with a lack of oxidative burst and there were no changes in ascorbate metabolism in response to UV-C treatment. Electron and fluorescence microscopy suggested the presence of three forms of cell death in the UV-C-treated AT1-beta/22 population: necrosis, apoptotic-like PCD, and autophagy. Taken together, the data reported here support a reduced DNA repair capability in carrot topo I-deficient cells while the putative relationship between topo I-depletion and ascorbate impairment is also discussed.
Balestrazzi
A
A
Department of Genetics and Microbiology, University of Pavia, Via Ferrata 1, Pavia, Italy.
Locato
V
V
Bottone
M G
MG
De Gara
L
L
Biggiogera
M
M
Pellicciari
C
C
Botti
S
S
Di Gesù
D
D
Donà
M
M
Carbonera
D
D
D001205:Ascorbic Acid / Q000378:metabolism*; D002478:Cells, Cultured; D004249:DNA Damage; D004264:DNA Topoisomerases, Type I / Q000172:deficiency* / Q000235:genetics; D018552:Daucus carota / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D014466:Ultraviolet Rays
D010940:Plant Proteins; D004264:DNA Topoisomerases, Type I; D001205:Ascorbic Acid