Figure 1.

The abo4-1 mutant shows increased tolerance to HU-induced replicative stress. A and B, Wild-type (Col-0) and abo4-1 mutant seedlings were germinated on HU-supplemented medium and plants with true leaves were counted after 12 d. The atr mutant was used as a hypersensitive control. In , values are average ± se of three biological replicates. Asterisks indicate statistically relevant differences with respect to the wild type in the same conditions (Student t test, P < 0.05). C to E, Wild type (Col-0) and abo4-1 mutant seedlings were grown for 4 d on half-strength MS and transferred to HU-supplemented medium (1 mM) for 9 d to monitor root growth. C, By contrast with wild-type plants, root length was almost unchanged by HU exposure in the abo4-1 mutant; arrowheads mark the position of the root tip. D, Average root length was measured after 9 d on HU; at least 20 plantlets were used for each treatment; values are average ± se. Different letters indicate significantly different values (Student t test, P < 0.05). Data are representative of two independent experiments. E, The relative growth of each genotype after 9 d on HU was calculated compared to untreated plants of the same genotype.