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Storage products and transcriptional analysis of the endosperm of cultivated wheat and two wild wheat species

100%

Uhlmann N. K., Beckles D. M.

Journal of Applied Genetics

2010

vol. 51

issue 4

431-447

The starch and protein in wheat (Triticum aestivum L.) endosperm provide 20% of the calories eaten by humans and were heavily selected for during domestication. We examined the main storage products and gene expression patterns that may embody compositional differences between two wild species Aegilops crassa and Aegilops tauschii and cultivated bread wheat. The storage product profiles differed significantly with T. aestivum accumulating twice as much carbon as the wild species, while the latter had 1.5 to 2-fold more total nitrogen per seed. Transcriptional analyses of endosperms of similar fresh weight were compared using a cDNA macroarray. Aegilops tauschii, and especially Ae. crassa had stronger hybridizations with storage protein sequences, but while there were differences in transcripts for starch biosynthetic genes, they were less dramatic. Of these, we cloned the Starch Branching Enzymes (SBE) IIa promoter region and the genomic clone of the Brittle-1 (Bt1) ADPglucose transporter. While Ae. crassa SBEIIa sequence was more divergent than that of Ae. tauschii's compared to bread wheat, there were no sequence polymorphisms that would explain the observed expression differences in Bt1 between these species. Furthermore, while there were nucleotide differences between Bt1 in Ae. crassa and bread wheat, they were synonymous at the amino acid level. Some of transcriptional differences identified here, however, deserve further examination as part of a strategy to manipulate wheat starch and protein composition.

Characterization of omega-secalin genes from rye, triticale, and a wheat 1BL/1RS translocation line

86%

Journal of Applied Genetics

2010

vol. 51

issue 4

403-411

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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2 Journal of Applied Genetics

2 2010

1 Beckles D. M.

1 Uhlmann N. K.

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Storage products and transcriptional analysis of the endosperm of cultivated wheat and two wild wheat species

Characterization of omega-secalin genes from rye, triticale, and a wheat 1BL/1RS translocation line