Submitted to: Plant and Animal Genome VX Conference Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/3/2004
Publication Date: 1/10/2005
Citation: Faris, J.D., Lu, H., Friesen, T.L., Haen, K.M., Fellers, J.P., Xu, S.S., Meinhardt, S.W. 2005. Targeting Tsn1 in wheat: colinearity with rice, chromosome walking, and marker-assisted selection. Plant and Animal Genome Abstracts. p. 195. Interpretive Summary:
Technical Abstract: The wheat Tsn1 gene confers sensitivity to a host-selective proteinaceous toxin (Ptr ToxA) produced by the tan spot fungus (Pyrenophora tritici-repentis). Tsn1 lies within a gene-rich region of chromosome 5B between deletions 5BL-14 and 5BL-9, which accounts for about 1 percent of the physical size of the long arm. Using RFLPs, ESTs, and AFLPs, we saturated the genomic region with 70 markers spanning about 50 cM. Assessment of the level of colinearity with rice using expressed sequences indicated a severe lack of conservation in this region. While small segments having apparent colinearity with rice chromosomes 3 and 9 were found, multiple breaks and interruptions occurred, and many expressed sequences were not present in the rice genome. We initiated chromosome walking using markers flanking Tsn1 at 0.2 and 0.4 cM, and have sequenced BAC contigs of 215 and more than 500 kb flanking the locus. Physical to genetic distance ratios ranged from 140-12,000 kb/cM. More than 20 putative genes were identified within the contigs, most of which are receptor and wall-associated kinases. Assessment of the level of colinearity between the putative genes in the contigs and rice revealed further interruptions and a lack of conservation at the micro level indicating it will be difficult to use rice as a vehicle for cloning Tsn1. Several microsatellite loci were identified within the BAC contigs and are currently being used for marker-assisted selection to transfer tsn1 to toxin-sensitive germplasm.