Characterisation of a gene encoding wheat endosperm starch branching enzyme-I

S. Rahman, Z. Li, S. Abrahams, D. Abbott, R. Appels, M. K. Morell

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Abstract

A genomic DNA fragment from Triticum tauschii, the donor of the wheat D genome, contains a starch branching enzyme-I (SBE-I) gene spread over 6.5 kb. This gene (designated wSBEI-D4) encodes an amino acid sequence identical to that determined for the N-terminus of SBE-I from the hexaploid wheat (T. aestivum) endosperm. Cognate cDNA sequences for wSBE I-D4 were isolated from hexaploid wheat by hybridisation screening from an endosperm library and also by PCR. A contiguous sequence (D4 cDNA) was assembled from the sequence of five overlapping partial cDNAs which spanned wSBEI-D4. D4 cDNA encodes a mature polypeptide of 87 kDa that shows 90% identity to SBE-I amino acid sequences from rice and maize and contains all the residues considered essential for activity. D4 mRNA has been detected only in the endosperm and is at a maximum concentration mid-way through grain development. The wSBE I-D4 gene consists of 14 exons, similar to the structure for the equivalent gene in rice; the rice gene has a strikingly longer intron 2. The 3' end of wSBEI-D4 was used to show that the gene is located on group 7 chromosomes. The sequence upstream of wSBE I-D4 was analysed with respect to conserved motifs.

Original languageEnglish
Pages (from-to)156-163
Number of pages8
JournalTheoretical and Applied Genetics
Volume98
Issue number1
DOIs
Publication statusPublished - 1999
Externally publishedYes

Keywords

  • Endosperm
  • Starch branching enzyme genes
  • Triticum tauschii
  • Wheat

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