Figure 6.

Increased DNA Damage in tso2-1 rnr2a-1 Seedlings.

(A) Results from the comet assay indicating the relative amount of DNA damage in different genotypes. Although tso2-1, rnr2b-1, or rnr2a-1 rnr2b-1 mutants exhibited levels of DNA damage similar to those in the wild type (Ler), tso2-1 rnr2a-1 double mutants exhibited an increased level of DNA damage even at 2 weeks old. The DNA damage level was increased further in 5-week-old tso2-1 rnr2a-1 plants. The extent of DNA damage in each nucleus is indicated by the units 0, 1, 2, 3, or 4. An increased unit correlated with a larger comet tail and a smaller comet head, as illustrated in the inset. The DNA damage units per genotype were derived by summing the units from 100 nuclei on each slide. Error bars represent sd values averaged from four slides.

(B) Twenty-seven to 30 cycles of RT-PCR were used to detect the induction of ATPARP1, ATPARP2, and ATRAD51 in 3-week-old seedlings. Lanes 1, 2, 3, and 4 correspond to the wild type (Ler), tso2-1, rnr2a-1 rnr2b-1, and tso2-1 rnr2a-1, respectively.