The expression of serine carboxypeptidases during maturation and germination of the barley grain.
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.
Dal Degan
F
F
Department of Physiology, Carlsberg Laboratory, Copenhagen Valby, Denmark.
Rocher
A
A
Cameron-Mills
V
V
von Wettstein
D
D
D000595:Amino Acid Sequence; D001483:Base Sequence; D002268:Carboxypeptidases / Q000096:biosynthesis* / Q000302:isolation & purification / Q000378:metabolism; D003001:Cloning, Molecular; D015342:DNA Probes; D015971:Gene Expression Regulation, Enzymologic; D015723:Gene Library; D017343:Genes, Plant; D001467:Hordeum / Q000201:enzymology / Q000502:physiology*; D007527:Isoenzymes / Q000096:biosynthesis* / Q000302:isolation & purification / Q000378:metabolism; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D012639:Seeds / Q000201:enzymology / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D015342:DNA Probes; D007527:Isoenzymes; D012313:RNA; D002268:Carboxypeptidases; C022633:serine carboxypeptidase