Main content area

The expression of serine carboxypeptidases during maturation and germination of the barley grain

Degan, F.D., Rocher, A., Cameron-Mills, V., Wettstein, D. von.
Proceedings of the National Academy of Sciences of the United States of America 1994 v.91 no.17 pp. 8209-8213
Hordeum vulgare, complementary DNA, carboxypeptidases, nucleotide sequences, amino acid sequences, gene expression, messenger RNA, seed development, aleurone layer, seed germination, endosperm, immunohistochemistry, structural genes
cDNA clones encoding three additional serine carboxypeptidases (Ser-CPs) have been isolated from a gibberellic acid-induced barley aleurone cDNA library. The three deduced Ser-CPs belong to the two-chain subfamily of Ser-CPs; they are synthesized as precursors with a putative signal peptide, propeptide, and linker peptide between the A and B chains. Their identification provides the proof for the existence of more than three Ser-CPs in cereal grains, and, based on their sequences, they may exhibit new substrate specificities. The expression of these and of the three previously isolated Ser-CPs from barley grains (CP-MI, CP-MII, and CP-MIII) has been investigated by Northern and Western analysis and RNA PCR. CP-MII is the only Ser-CP to be expressed and accumulate in the developing grain and is stored in its active form in the mature grain. All six Ser-CPs are expressed de novo in the germinating grain, in the scutellum, and/or in the aleurone. Furthermore, at least CP-MI, CP-MII, and CP-MIII are secreted into the endosperm. In addition, all Ser-CPs (except CP-MI) are also expressed in the roots and shoots of the growing seedling. This enzyme family thus appears to be ubiquitous in the barley plant, which suggests that Ser-CPs play additional roles besides their participation in the mobilization of storage proteins.