Figure 2.

The induction of CPDs as assayed via alkaline Southern increases linearly with UV-B dose. Five-day-old Arabidopsis seedlings grown on 1% agarose plates were exposed to 0, 2.2, 4.8, and 6 kJ/m² of UV-B. Seedlings were immediately harvested in liquid nitrogen after irradiation. DNA samples were digested with BstEII, and divided into two equal aliquots. One aliquot of each sample was subsequently digested with T4 endo V. The digests were run on alkaline gels, and Southern blots were probed with a double strand ³²P labeled probe with a 1.5-kb double-stranded fragment of the RPII gene. Signals produced by the probe were measured via phosphorimager. The “0 UV-B” serves as a control for non-specific nuclease activities in the T4 endo V. Values are derived from a minimum of 10 paired (T4 endo+/T4endo−) lanes representing three biological repeats for each UV dose.