Fig. 6. The CArG box at nt –400 of the SOC1 promoter mediates repression of SOC1::GUS expression in 35S::FLC lines. (A) Mutation of the CArG box at nt –400 leads to derepression of SOC1::GUS expression in 35S::FLC lines. Ten-day-old seedlings were stained for GUS activity. (a) One kilobase SOC1::GUS expression in a 35S::FLC control seedling (left); three independent lines showing 1 kb ΔCArG SOC1::GUS expression in 35S::FLC seedlings (right); (b) 300 bp C SOC1::GUS expression in a wild-type (WT) seedling and in a 35S::FLC seedling; (c) mutated 300 bp C ΔCArG SOC1::GUS expression in a WT seedling and in a 35S::FLC seedling. (B) Analysis of the effect of the CArG box mutation on SOC1::GUS activation in 35S::CO lines and repression in 35S::FLC lines. Expression of WT and mutated ΔCArG reporter genes was monitored in WT, 35S::CO and 35S::FLC seedlings by northern blotting using probes for GUS and UBQ10 (loading control). The data were quantified and are presented in histogram format.