A cDNA, cRKIN1, encoding a putative homologue of the yeast (Saccharomyces cerevisiae) SNF1-encoded protein-serine/threonine kinase, has been isolated from a library prepared from rye endosperm mRNA. Northern blot analysis demonstrated the presence of cRKIN1-related transcripts in developing endosperms but not in shoots, and Southern blot analysis showed the presence of a small gene family. SNF1 plays a central role in carbon catabolite repression in yeast and expression of the RKIN1 sequence in yeast snf1 mutants restored SNF1 function. This suggests that the RKIN1 protein has a role in the control of carbon metabolism in endosperms of rye.