Structure of Brassica napus phosphoenolpyruvate carboxylase genes: missing introns causing polymorphisms among gene family members.

The Brassica napus genome contains more than four phosphoenolpyruvate carboxylase (PEPCase) genes. Although the nucleotide sequences of these genes highly resemble each other, an intron corresponding to the 7th intron in the maize gene is present in PE15- and PE105-PEPCase genes but absent in PE3-PEPCase. The intron corresponding to the maize 3rd intron is absent in PE15- and PE105-PEPCase genes. Deletion of these introns occurred precisely such that the coding sequence is faithfully preserved with respect to the maize gene. The PE19-PEPCase gene contains a deletion in the 8th exon instead of the presence of those introns.