ATR1 transcript levels are elevated in the atr1D mutant. Total RNA was prepared from 2-week-old seedlings of wild-type Col (ATR1) or Col atr1D (atr1D) grown on unsupplemented PNS medium. Duplicate Northern blots of these samples were probed with an ATR1 cDNA probe (ATR1, 1-week exposure), an ASA1 cDNA probe (ASA1, 1-week exposure), or an RLK1 probe (RLK1, 1-week exposure). The blots were then stripped and reprobed with an α tubulin probe (TUB, 24-hr exposure) as a normalization control. The ATR1 blot reprobed with TUB is shown here. The quantitated ratio of transcripts detected in atr1D relative to ATR1 after normalization to TUB is given as the average of three independent experiments.