Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Characterizing The Hexaploid Wheat Genome By Sequencing And Mapping Random BAC Clones

Katrien M. Devos^1,2 , Jianxin Ma³ , Ana C. Pontaroli³ , Jeffrey L. Bennetzen³

¹  Dept. of Crop and Soil Sciences, University of Georgia, Athens, GA 30602, USA

²  Dept. of Plant Biology, University of Georgia, Athens, GA 30602, USA

³  Dept. of Genetics, University of Georgia, Athens, GA 30602, USA

There is considerable interest from the scientific community in sequencing the genome of bread wheat, an allohexaploid with a large genome (2n=6x=42; C=17,000 Mb). Sequencing 17,000 Mb of DNA, however, requires the adoption of sequencing strategies that will target more than 90% of the genes and little of the repetitive DNA. Suggested approaches include the use of gene-enrichment technologies such as high Cot and enrichment for hypomethylated sequences, techniques that have been pioneered in maize. Sequencing only gene-rich BACs has been the approach taken for the Lotus japonicus genome.
The current view of the organization of the wheat genome is that genes are clustered in gene-rich areas. It has even been suggested that some 94% of the genes may be present in only 29% of the genome (Erayman et al. 2004). This hypothesis is based on EST densities in chromosome bins delineated by overlapping sets of deletion lines and is to some extent supported by sequence data obtained from BAC clones preselected to contain a gene of interest, mainly disease resistance and storage protein genes. We aim to test this model of compartmentalization of genes in gene-rich and gene-poor regions by sequencing and annotating 220 randomly selected BAC clones. The BAC clones, irrespective of their gene content, will be placed in the chromosome bins using a newly developed mapping strategy. This will allow us to correlate gene content with previously established regions of high and low gene density. Initial data suggests that genes may be more evenly distributed over the genome than previously thought and further substantiates the need for large-scale random BAC sequencing to analyze the organization of genes in the hexaploid wheat genome.