Plant, Animal & Microbe Genomes X Conference

January 12-16, 2002
Town & Country Convention Center
San Diego, CA

Poster: Large Insert Libraries
            

THE NBS-LRR GENE FAMILY IN THE SOYBEAN GENOME IS ORGANIZED AND EVOLVES BY A PROCESS OF BIRTH-AND-DEATH, SUPERCLUSTER FORMATION AND ADAPTIVE SELECTION

¹ Depart. of Soil and Crop Sci. and IPGB, Texas A & M University, College Station, TX77843-2123

² Depart. of Plant Soil and General Agric., Southern Illinois University at Carbondale, Carbondale, IL62901-4415

The NBS-LRR gene family is one of the largest multigene families in plant kingdom, which provides most of the resistance genes to plant pathogens. This research represents the first report on the organization and evolution of this gene family in a large genome at the whole-genome level. We have screened a soybean BAC library using the probes representing eight subfamilies of the soybean NBS-LRR gene family, identified 862 positive BACs, fingerprinted and assembled them into 96 contigs and 366 singletons, and positioned each subfamily to the contigs and singletons. The results indicated that the soybean NBS-LRR family is clustered at about 462 loci in the genome and the members of each cluster are often physically clustered within a close distance. The clusters of the family are made up of 48 combinations of the eight subfamilies and the frequency of each of them is non-random. Comparative analysis unveiled that the member makeup of a cluster was not necessarily correlated with their phylogenetic relationships. Of the 462 clusters 299 were monophyletic, whereas 163 were polyphyletic. These results have led to a hypothesis that the NBS-LRR gene family is organized and evolves through a process of birth-and-death, supercluster formation, and adaptive selection. This model has explained the results not only from this study, but also from others.