Characterization of omega-secalin genes from rye, triticale, and a wheat 1BL/1RS translocation line
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Sixty-two DNA sequences for the coding regions of omega-secalin (-secalin) genes have been characterized from rye (Secale cereale L.), hexaploid and octoploid triticale (x Triticosecale Wittmack), and wheat (Triticum aestivum L.) 1BL/1RS translocation line. Only 19 out of the 62 omega-secalin gene sequences were full-length open reading frames (ORFs), which can be expressed into functional proteins. The other 43 DNA sequences were pseudogenes, as their ORFs were interrupted by one or a few stop codons or frameshift mutations. The 19 -secalin genes have a typical primary structure, which is different from wheat gliadins. There was no cysteine residue in -secalin proteins, and the potential celiac disease (CD) toxic epitope (PQQP) was identified to appear frequently in the repetitive domains. The -secalin genes from various cereal species shared high homology in their gene sequences. The omega-secalin gene family has involved fewer variations after the integration of the rye R chromosome or whole genome into the wheat or triticale genome. The higher Ka/Ks ratio (i.e. non-synonymous to synonymous substitutions per site) in omega-secalin pseudogenes than in -secalin ORFs indicate that the pseudogenes may be subject to a reduced selection pressure. Based on the conserved sequences of omega-secalin genes, it will be possible to manipulate the expression of this gene family in rye, triticale, or wheat 1BL/1RS translocation lines, to reduce its negative effects on grain quality.
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Y-L. Zheng, Triticeae Research Institute, Sichuan Agricultural University, Ya?an, Sichuan, 625014, China