Submitted to: Chromosoma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2004
Publication Date: 2/18/2004
Citation: Zhang, P., Li, W., Fellers, J.P., Friebe, B., Gill, B.S. 2004. Bac fish in wheat identifies chromosome landmarks consisting of different types of transposable elements. Chromosoma (2004). 112:288-299. Interpretive Summary: The focus of this research was to understand wheat chromosome structure and the DNA make up of those chromosome segments. The era of genomics has allowed for the isolation of DNA sequences that are specific to regions of chromosomes. The reported research took several clones, labeled them with a fluorescent dye, and hybridized them to chromosomes mounted on a slide. The DNA clones were found to be very specific in where they bound to the chromosomes: one to the centromere region of wheat and other cereals except rice; one to the sub telomere region of wheat, one to five different D chromosomes in wheat, and four clones that hybridized to only the long arm of chromosome 4A. All of the clones were different repetitive DNA sequences; however, this work showed that they were specific in where they hybridized. These are new tools that can be used to isolate and identify specific chromosomes and chromosome segments.
Technical Abstract: Fluorescence in situ hybridization (FISH) has been widely used in the physical mapping of genes and chromosome landmarks in plants and animals. Bacterial artificial chromosomes (BACs) contain large inserts making them amenable for FISH mapping. We used BAC-FISH to study genome organization and evolution in hexaploid wheat and its relatives. We selected 56 restriction fragment length polymorphism (RFLP) locus specific BAC clones from libraries of Aegilops tauschii (the D-genome donor of hexaploid wheat) and A-genome diploid Triticum monococcum. Different types of repetitive sequences were identified using BAC-FISH. TwoBAC clones gave FISH patterns similar to the repetitive DNA family pSc119; one BAC clone gave a FISH pattern similar to the repetitive DNA family pAs1. In addition, we identified several novel classes of repetitive sequences: one BAC clone hybridized to the centromeric regions of wheat and other cereal species, except rice; one BAC clone hybridized to all subtelomeric chromosome regions in wheat, rye, barley and oat; one BAC clone contained a localized tandem repeat and hybridized to five D-genome chromosome pairs in wheat; and four BAC clones hybridized only to a proximal region in the long arm of chromosome 4A of hexaploid wheat. These repeats are valuable markers for defined chromosome regions and can also be used for chromosome identification. Sequencing results revealed that all these repeats are transposable elements (TEs), indicating the important role of TEs, especially retrotransposons, in genome evolution of wheat.o isolate and identify specific chromosomes and chromosome parts.