Abstract: Transcription co-repressors are negative regulators of gene expression. Since they do not possess a DNA-binding motif, their ability to repress gene expression depends on their association with other DNA-binding transcription factors. One well characterized transcription co-repressor is the yeast Tup1. Although unable to bind DNA by itself, the Tup1 co-repressor is recruited by different DNA-binding transcription factors to repress pathway-specific gene expression. Recent isolations of two Arabidopsis genes,LEUNIG (LUG) and SEUSS (SEU),suggest that similar types of co-repressors are involved in the transcription repression of floral homeotic genes during flower development.This review will summarize these findings, speculate on mechanisms, and discuss future directions.