Submitted to: Plant Molecular Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/7/2001
Publication Date: 3/1/2002
Citation: BOYKO,E., KALENDAR,R., KORZUN,V., FELLERS,J.P., KOROL,A., SCHULMAN,A.H., GILL,B.S., A HIGH-DENSITY CYTOGENTIC MAP OF THE AEGILOPS TAUSCHII GENOME INCORPORATING RETROTRANSPOSONS AND DEFENSE-RELATED GENES: INSIGHTS INTO CEREAL CHROMOSOME STRUCTURE AND FUNCTION, PLANT MOLECULAR BIOLOGY, 2002. Interpretive Summary: The wild wheat relative Aegilops tauschii, has conserved gene order, in comparison to bread wheat. This work updated the molecular and genetic map of A. tauschii with new markers. These included repetitive sequences called microsatellite, jumping genes called retrotransposon, and DNA markers similar to disease resistance genes. There was a correlation between the amount of genes and the number of markers present in that location. Also, the impact of these densities and their specificity to chromosome arms are discussed in this paper. The new map will be useful for indentifying economically important genes in wheat.
Technical Abstract: Aegilops tauschii (Coss.) Schmal. (2n=2x=14, DD) (syn. A. squarrosa L.; Triticum tauschii) is well known as the D-genome donor of bread wheat (T. aestivum, 2n=6x=42, AABBDD). Because of conserved synteny, a high-density map of the A. tauschii genome will be useful for breeding and genetics within the tribe Triticeae which besides bread wheat also includes barley and rye. We have placed 249 new loci onto a high-density integrated cytological and genetic map of A. tauschii for a total of 732 loci making it one of the most extensive maps produced to date for the Triticeae species. Of the mapped loci, 160 are defense-related genes. The retrotransposon marker system recently developed for cultivated barley (Hordeum vulgare L.) was successfully applied to A. tauschii with the placement of 80 retrotransposon loci onto the map. A total of 50 microsatellite and ISSR loci were also added. Most of the retrotransposon loci, resistance (R), and defense-response (DR) genes are organized into clusters: retrotransposon clusters in the pericentromeric regions, R and DR gene clusters in distal/telomeric regions. Markers are non-randomly distributed with low density in the pericentromeric regions and marker clusters in the distal regions. A significant correlation between the physical density of markers (number of markers mapped to the chromosome segment/physical length of the same segment in [mgr]m) and recombination rate (genetic length of a chromosome segment/physical length of the same segment in [mgr]m) was demonstrated. Discrete regions of negative or positive interference (an excess or deficiency of crossovers in adjacent intervals relative to the expected rates on the assumption of no interference) was observed in most of the chromosomes. Surprisingly, pericentromeric regions showed negative interference. Islands with negative, positive and/or no interference were present in interstitial and distal regions. Most of the positive interference was restricted to the long arms. The model of chromosome structure and function in cereals with large genomes that emerges from these studies is discussed.