The two genes encoding starch-branching enzymes IIa and IIb are differentially expressed in barley.
The sbeIIa and sbeIIb genes, encoding starch-branching enzyme (SBE) IIa and SBEIIb in barley (Hordeum vulgare L.), have been isolated. The 5' portions of the two genes are strongly divergent, primarily due to the 2064-nucleotide-long intron 2 in sbeIIb. The sequence of this intron shows that it contains a retro-transposon-like element. Expression of sbeIIb but not sbeIIa was found to be endosperm specific. The temporal expression patterns for sbeIIa and sbeIIb were similar and peaked around 12 d after pollination. DNA gel-blot analysis demonstrated that sbeIIa and sbeIIb are both single-copy genes in the barley genome. By fluorescence in situ hybridization, the sbeIIa and sbeIIb genes were mapped to chromosomes 2 and 5, respectively. The cDNA clones for SBEIIa and SBEIIb were isolated and sequenced. The amino acid sequences of SBEIIa and SBEIIb were almost 80% identical. The major structural difference between the two enzymes was the presence of a 94-amino acid N-terminal extension in the SBEIIb precursor. The (beta/alpha)8-barrel topology of the alpha-amylase superfamily and the catalytic residues implicated in branching enzymes are conserved in both barley enzymes.
Sun
C
C
Department of Biochemistry, The Arrhenius Laboratories, Stockholm University, S-106 91 Stockholm, Sweden.
Sathish
P
P
Ahlandsberg
S
S
Jansson
C
C
D015061:1,4-alpha-Glucan Branching Enzyme / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D001467:Hordeum / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D017404:In Situ Hybridization, Fluorescence; D007438:Introns; D007527:Isoenzymes / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
D017931:DNA Primers; D018076:DNA, Complementary; D018744:DNA, Plant; D007527:Isoenzymes; D015061:1,4-alpha-Glucan Branching Enzyme; C112590:starch-branching enzyme II