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.