The sequence variation responsible for the functional difference between the CONSTANS protein, and the CONSTANS-like (COL) 1 and COL2 proteins, resides mostly in the region encoded by their first exons

► Differences in the roles played by CO, COL1, and COL2 proteins in flowering. ► The importance of the first exon of CO in promoting flowering. ► Domain swapping and site-directed mutagenesis.