Promoters of three Brassica rapa FLOWERING LOCUS C differentially regulate gene expression during growth and development in Arabidopsis

FLOWERING LOCUS C (FLC) is a MADS-domain transcription factor that acts as a dosage-dependent repressor of flowering time. Three FLC-encoding Brassica rapa genes, BrFLC1, 2, and 3, were previously identified as being possibly expressed in other parts of B. rapa. The relative activities of the 5'-upstream 2-kb promoter regions of the BrFLC1, 2, and 3 genes were investigated and shown to differentially drive expression of a beta-glucuronidase (GUS) reporter gene in transgenic Arabidopsis thaliana. The GUS expression driven by these three BrFLC promoters showed distinct spatial and temporal patterns during plant growth and development. In particular, GUS expression by the BrFLC3 promoter was found predominantly in all vegetative tissues excluding roots, as well as in the styles, stigma papillae, filaments, and silique-abscission zones. GUS activity induced by the BrFLC2 promoter was stronger in the roots than in other vegetative tissues, and was seen in the stigma papillae and in the abscission zones of the siliques. GUS expression driven by the BrFLC1 promoter, however, was observed only in the apical meristems during vegetative growth, and in the stigmata and pollen grains. These results suggest that the three BrFLC promoters induce differential tissue-specific expressions for the respective genes at various stages of growth and development.