Figure 8.

Analysis of a tdp1-4 mus81-1 Double Mutant.

(A) Although tdp1-4 and mus81-1 lines were indistinguishable from wild-type (WT) plants, the tdp1-4 mus81-1 double mutant line exhibited a growth defect that was characterized by a reduced plant size compared with both single mutants. The picture was taken after 7 weeks of cultivation on soil.

(B) Mean values of plantlet fresh weights of the tdp1-4 mus81-1 double mutant, the corresponding single mutant lines, and the wild type, relative to untreated controls after treatment with 100 and 150 nM CPT (n = 6). Although tdp1-4 did not show a hypersensitivity, mus81-1 lines exhibited a decreased relative fresh weight compared with wild type. The respective double mutant was only hypersensitive on mus81-1 level.

(C) and (D) Mean values of PI-stained root tips (10 per line) of the tdp1-4 mus81-1 double mutant, the corresponding single mutant lines, and the wild type after induction with 3 nM CPT (n = 3). Although tdp1-4 was comparable with wild type, exhibiting less than one dead cell per root, mus81-1 showed 8 dead cells per root. The rate of cell death in root meristems was significantly elevated in the respective double mutant, with a number of 12 dead cells per root.

(E) Wild type, tdp1-4, mus81-1, and the corresponding double mutant were treated with 2.5 and 5 µM cis-platin (cis-Pt) and the fresh weight relative to an untreated control was determined. Mean values of plantlet fresh weights are given (n = 3). The double mutant line exhibited a hypersensitivity on the level of the mus81-1 single mutant line. Tdp1-4 did not display a sensitivity and its relative fresh weight was comparable with wild type.

Columns in (B), (C), and (E) correspond to mean values, and error bars represent ±sd. Statistical differences were calculated using a two-tailed t test with unequal variances: *P < 0.05, **P < 0.01, ***P < 0.001.