The sequence of a gene encoding convicilin from pea (Pisum sativum L.) shows that convicilin differs from vicilin by an insertion near the N-terminus

Abstract

The sequence of a gene encoding convicilin, a seed storage protein in pea (Pisum sativum L.), is reported. This gene, designated cvcA, is one of a sub-family of two active genes. The transcription start of cvcA was mapped. Convicilin genes are expressed in developing pea seed cotyledons, with maximum levels of the corresponding mRNA species present at 16-18 days after flowering. The gene sequence shows that convicilin is similar to vicilin, but differs by the insertion of a 121-amino-acid sequence near the N-terminus of the protein. This inserted sequence is very hydrophilic and has a high proportion of charged and acidic residues; it is of a similar amino acid composition to the sequences found near the C-terminal of the alpha-subunit in pea legumin genes, but is not directly homologous with them. Comparison of this sequence with the ‘inserted’ sequence in soya-bean (Glycine max) conglycinin (a homologous vicilin-type protein) suggests that the two insertions were independent events. The 5′ flanking sequence of the gene contains several putative regulatory elements, besides a consensus promoter sequence.