Figure 7. DNA damage level is higher in the parg1-4 mutant than that in Col-0 plants under genotoxic stress.

(A) Expression level changes of genes involved in DNA double-strand break repair in roots of Col-0 and parg1-4 seedlings. The data represent the mean values of three replicates ± SD. (C) control; (B) bleomycin at 20 μg ml⁻¹. (B) Comet assay of the DNA damage levels of Col-0 and parg1-4 seedlings grown on plates with or without (control) 20 μg ml⁻¹ bleomycin for 10 days. The percentage of DNA in comet tails was analyzed and quantified by CASP software (http://sourceforge.net/projects/casp/) and used as an indicator of DNA damage level. 100 nuclei for each treatment were randomly selected and imaged. The bar size represents proportion of nuclei falling into the ranges of damage level indicated by different colors, and the images with percentages beside it indicate the examples of damaged nuclei. (C) DNA fragmentation assay showed that genomic DNA is more damaged in parg1-4 than in Col-0.