Plant & Animal Genomes XIII Conference Plant & Animal Genomes XIII ConferenceJanuary 15-19, 2005
Town & Country Convention Center
San Diego, CA
K Shopinski , MJ Iqbal , J Shultz , Chet Langin , N Lavu , DA Lightfoot
The aim was to physically locate genes on the soybean physical map for positional cloning of resistance loci and for genome architecture analysis. Used were 309 expressed sequence tags (EST) related to plant defense and 13,473 BES that predicted 2,111 gene models. About 53% had homology to genes of known function. Genes were located using BACs from three bacterial artificial chromosome (BAC) libraries that represented a Minimum Tiling Path (MTP) of the Forrest genome. Southern hybridization to some BAC DNA restriction fragments showed very few colony hybridizations were false positives. Gene clusters were found on linkage groups A1, B1, C2, E, D1AQ, G, I, M, H, and O but did not overlap with the known disease resistance loci (on G, C2, I and N). Clustering of some defense related genes suggest certain genomic regions are dedicated to specific tasks. Gene clusters appeared to correlate well with the chromosome ideotypes of euchromatin distribution, repeats were most common in heterochromatic regions. Among the gene families analyzed 35% were present as single genes, 25% had 2 members, 11% had 3 members, 10% had 4 members, 4% had 5 members and 15% had more than 5 members. Compared to Arabidopsis there were more 2 and 4 gene families reflecting the diploidized-tetraploid nature of the soybean genome. However, there were fewer families with 5 or more genes and the same number of single gene families suggesting extensive selective gene loss or rapidly divergent evolution to regenerate the unique genes following the last ploidy shift.