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Theor Appl Genet (2008) 116:953966 DOI 10.1007/s00122-008-0727-1
ORIGINAL PAPER
Molecular characterization and genomic organizationof low molecular weight glutenin subunit genesat the Glu-3 loci in hexaploid wheat (Triticum aestivum L.)
Xiu-Qiang Huang Sylvie Cloutier
Received: 5 October 2007 / Accepted: 1 February 2008 / Published online: 28 February 2008 Springer-Verlag 2008
Abstract In this study, we report on the molecular characterization and genomic organization of the low molecular weight glutenin subunit (LMW-GS) gene family in hexaploid wheat (Triticum aestivum L.). Eighty-two positive BAC clones were identiWed to contain LMW-GS genes from the hexaploid wheat Glenlea BAC library via Wlter hybridization and PCR validation. Twelve unique LMW glutenin genes and seven pseudogenes were isolated from these positive BAC clones by primer-template mismatch PCR and subsequent primer walking using hemi-nested touchdown PCR. These genes were sequenced and each consisted of a single-open reading frame (ORF) and untranslated 5[H11032] and 3[H11032] Xanking regions. All 12 LMW glutenin subunits contained eight cysteine residues. The LMW-m-type subunits are the most abundant in hexaploid wheat. Of the 12 LMW-GS, 1, 2 and 9 are i-type, s-type and m-type, respectively. The phylogenetic analysis suggested that the LMW-i type gene showed greater diVerences to LMW-s and LMW-m-type genes, which, in turn, were more closely related to one another. On the basis of their N-terminal
sequences, they were classiWed into nine groups. Fingerprinting of the 82 BAC clones indicated 30 BAC clones assembled into eight contigs, while the remaining clones were singletons. BAC end sequencing of the 82 clones revealed that long terminal repeat (LTR) retrotransposons were abundant in the Glu-3 regions. The average physical distance between two adjacent LMW-GS genes was estimated to be 81 kb. Most of LMW-GS genes are located in the D-genome, suggesting that the Glu-D3 locus is much larger than the Glu-B3 locus and Glu-A3 locus. Alignments of sequences indicated that the same type (starting with the same N-terminal sequence) LMW-GS genes were highly conserved in the homologous genomes between hexaploid wheat and its donors such as durum wheat and T. tauschii.
Keywords BAC clones BAC Wngerprinting Chromosomal location Genomic organization Hexaploid wheat LMW-GS
Introduction
Seed storage proteins play an important role in determining wheat (Triticum aestivum L.) quality (Payne 1987). The major seed storage proteins are called prolamins because...