A full-length cDNA clone from hexaploid bread wheat, encoding the smal
l subunit of ADP-glucose pyrophosphorylase, has been isolated from an
endosperm cDNA library. The cDNA insert has an open reading frame whic
h encodes a protein of 473 amino acids (52.1 kDa). The presence of a c
hloroplast/amyloplast transit peptide of 22 amino acids is proposed. T
he deduced amino acid sequence exhibits a high degree of homology with
the small subunit ADP-glucose pyrophosphorylase proteins from rice (w
ith 90% of identical amino acids) and potato (with 86% of identical am
ino acids) and contains conserved sequence elements which are thought
to represent the substrate binding and allosteric activator sites. The
genes are organised as single-copy loci on chromosomes 7A, 7B and 7D
in the wheat genome and are highly expressed during grain development.
Homologous transcripts are expressed in leaves and roots.