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Promoter and coding sequences of puroindoline a and b in the wild progenitors of hexaploid wheat. M.
Lillemo (1), M. Simeone (2), and C. F. Morris (2). (1) Department of Horticulture and Crop Sciences,
Agricultural University of Norway, PO Box 5022, N-1432 Ås, Norway; (2) USDA-ARS, Western Wheat
Quality Lab, Washington State University, Pullman, WA 99164-6394, USA.
Grain hardness is the single most important trait in determining the
classification and utilization of wheat (Triticum eastivum L.). The molecular basis for this trait is
determined by the puroindoline a and b proteins, which coding sequences have been located close to the
telomere of chromosome 5DS. Puroindolines are basic and cystine-rich proteins with a characteristic
tryptophan-rich domain which make them unique among plant proteins. Puroindoline a and b share 70.2%
identity in their coding sequences. Most probably, homeologous sequences for puroindoline a and b also
exist on chromosomes 5AS and 5BS, but these genes are suggested to be inactive since no transcripts can be
detected in durum wheat (Triticum turgidum L. var. durum, AABB). To investigate this
further, we have sequenced puroindoline a and b in some accessions of the suggested wild diploid
progenitors of hexaploid wheat, T. urartu (AA), T. monococcum (AA), Aegilops
speltoides (BB) and A. tauschii (DD), and also obtained 1.3-2.5 kb of their upstream promoter
sequences by inverse PCR. Both the analysed promoter sequences and western blots of Triton X114
extracted proteins on SDS-PAGE are consistent with expression of puroindoline a and b in these wild
diploid species. Comparison of the deduced amino acid sequences of puroindoline a and b from the wild
diploid AA and BB genomes showed 95.9 to 97.3% sequence identity with puroindoline a and b on
chromosome 5DS in common wheat.
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