Sites hypersensitive to digestion by DNase I have been identified within the 5'-flanking and 3'-coding sequences of genes encoding the defense enzyme chalcone synthase in bean (Phaseolus vulgaris L.). Two of the 5'-flanking hypersensitive sites are markedly induced upon elicitation of cells with glutathione and delineate sequence elements that are also present in the promoters of coordinately regulated genes. In contrast, other hypersensitive sites within the 5'-flanking sequences are expressed constitutively and one maps within an element that is also present in the promoters of coordinately regulated genes. These results suggest that the transcriptional activation of chalcone synthase genes is accompanied by structural changes in the chromatin associated with the proximal region of the promoter and that these probably reflect the binding of transcription factors tocis-regulatory elements.