Figure 6.

Regulatory Regions of FLC.

(A) Representation of the FLC sequence contained within the 6-kb construct. GAGAG sites and potential PHO and Zeste recognition motifs are indicated (asterisk, triangle, and Z, respectively). FLC segment, nucleotide numbering, and shading are as in Figure 1.

(B) Regions sufficient for vernalization (V)-induced repression of FLC expression, as inferred from the Δ2.8 construct and the 272-bp promoter construct. A construct with 272 bp of promoter and with the 2.8-kb deletion from intron I was not tested for its response to vernalization.

(C) Region required for the maintenance of vernalization-induced repression. The entire region is not required, because partial deletions in the Δ1.2 and Δ1.3 constructs directed stable repression.

(D) Region containing potential negative regulatory elements.

(E) Region containing potential positive regulatory elements.

(F) Regions sufficient for expression in nonvernalized plants, as inferred from the Δ2.8 construct and the 272-bp promoter construct. The GUS activity in a construct with 272 bp of promoter and with the 2.8-kb deletion from intron I was not tested.

(G) The repression of FLC expression by FCA requires the 4-kb intragenic region. We have not determined whether the promoter sequence is required in addition to the intragenic region.