Comparison of starch-branching enzyme genes reveals evolutionary relationships among isoforms. Characterization of a gene for starch-branching enzyme IIa from the wheat genome donor Aegilops tauschii.
Genes and cDNAs for starch-branching enzyme II (SBEII) have been isolated from libraries constructed from Aegilops tauschii and wheat (Triticum aestivum) endosperm, respectively. One class of genes has been termed wSBEII-DA1 and encodes the N terminus reported for an SBEII from wheat endosperm. On the basis of phylogenetic comparisons with other branching enzyme sequences, wSBEII-DA1 is considered to be a member of the SBEIIa class. The wSBEII-DA1 gene consists of 22 exons with exons 4 to 21 being identical in length to the maize (Zea mays) SBEIIb gene, and the gene is located in the proximal region of the long arm of chromosome 2 at a locus designated sbe2a. RNA encoding SBEIIa can be detected in the endosperm from 6 d after flowering and is at its maximum level from 15 to 18 d after anthesis. Use of antibodies specific for SBEIIa demonstrated that this protein was present in both the soluble and granule bound fractions in developing wheat endosperm. We also report a cDNA sequence for SBEIIa that could arise by variant transcription/splicing. A second gene, termed wSBEII-DB1, was isolated and encodes an SBEII, which shows greater sequence identity with SBEIIb-type sequences than with SBEIIa-type sequences. Comparisons of SBEII gene structures among wheat, maize, and Arabidopsis indicate the lineage of the SBEII genes.
Rahman
S
S
Commonwealth Scientific and Industrial Research Organization Plant Industry, P.O. Box 1600, Australian Capital Territory 2601, Australia. s.rahman@pi.csiro.au
Regina
A
A
Li
Z
Z
Mukai
Y
Y
Yamamoto
M
M
Kosar-Hashemi
B
B
Abrahams
S
S
Morell
M K
MK
D015061:1,4-alpha-Glucan Branching Enzyme / Q000737:chemistry / Q000235:genetics*; D000595:Amino Acid Sequence; D018076:DNA, Complementary; D019143:Evolution, Molecular; D018745:Genome, Plant; D017404:In Situ Hybridization, Fluorescence; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D014908:Triticum / Q000201:enzymology / Q000235:genetics*
D018076:DNA, Complementary; D007527:Isoenzymes; D015061:1,4-alpha-Glucan Branching Enzyme; C112590:starch-branching enzyme II