An expressed napin storage protein gene from Brassica rapa, BcNA1, has been cloned and sequenced. The gene is a member of a family of four to seven napin genes in B. rapa and is highly expressed in developing seeds. An expression cassette containing the DNA flanking the napin coding region of BcNA1 has been engineered and demonstrated to function appropriately, as compared with the gene's endogenous expression, in transgenic rapeseed using the β-glucuronidase reporter gene. The B. rapa BcNA1 gene and a B. napus napin gene, gNa, share extremely high nucleotide homology not only throughout their coding regions, but over a DNA locus comprising 4.3 kb. We suggest the gNa gene was contributed by the original B. rapa progenitor of the amphidiploid B. napus.