Abstract
We have cloned and sequenced 115 repeat units of the 5S rDNA genes and spacers from wheat (Triticum) and the polyploid wheat progenitor, Aegilops, and analyzed them together with sequences available in GenBank® (National Center for Biotechnology Information, NCBI, NLM, NIH, Bethesda, Maryland, USA). We were able to assort the sequences into nine orthologous groups which we call unit classes. The following unit classes were assigned to haplomes, and labeled accordingly: long A1, short A1, short A2, long G1, short G1, long D1, short D1, long S1 and short S1. The AA-genome, DD-genome and SS-genome species were each found to contain a long and a short class. The AAGG-genome species T. timopheevii and the AAAtAtGG-genome species T. zhukovskyi, both contain the long A1, long G1 and short G1 unit classes. The AABB-genome species T. turgidum consists of the short A2, a unit class not yet found in T. monococcum, and the long S1 unit class found in the species of Aegilops section Sitopsis. The bread wheat AABBDD-genome contains the long A1, short A2, long D1, long S1 and short G1 unit classes. The presence of the long S1, also demonstrated to occur in both T. turgidum and T. aestivum, supports the hypothesis that the progenitor of the B-haplome in wheat originated in Aegilops section Sitopsis. The presence of the short G1 unit class, i.e. the G-haplome in bread wheat, is unexpected. These new findings are discussed in the light of published findings, especially those relating to 5S DNA loci and evolutionary hypotheses.
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Baum, B.R., Bailey, L.G. The 5S rRNA gene sequence variation in wheats and some polyploid wheat progenitors (Poaceae: Triticeae). Genetic Resources and Crop Evolution 48, 35–51 (2001). https://doi.org/10.1023/A:1011263107219
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DOI: https://doi.org/10.1023/A:1011263107219