Plant & Animal Genomes XI Conference

January 11-15, 2003
Town & Country Convention Center
San Diego, CA

Poster: Genome Sequencing & ESTs
            

COMPARATIVE SEQUENCING OF A RESISTANCE GENE ISLAND IN THE D GENOME OF WHEAT.

¹ Deptment of Plant Pathology, Kansas State University, Manhattan, KS 66506

² USDA-ARS, Dept. of Plant Pathology, Kansas State University, Manhattan, KS 66506

³ USDA-ARS, Northern Crop Science Lab, North Dakota State University, Fargo, ND 58105

The wheat genome is segregated into regions of high gene density and highly repetitive gene-poor regions. The telomeric regions of wheat chromosomes are typically gene-rich and highly recombinogenic. Sequence analysis revealed a cluster of three defense related genes within a 46 Kb gene island at the end of chromosome 1DS. CDS3 is a LZ-NBS-LRR class RGA that is highly homologous to the putative stripe rust resistance gene Yr10, CDS5 is homologous to the putative cereal cyst nematode resistance gene Cre3, and CDS7 is homologous to an HCBT-like PR gene from Arabidopsis. Gene expression profiles show that CDS3 is root specific, CDS5 is constitutive-seedling specific, and PR gene CDS7 is induced in a resistance reaction. Comparative sequencing of this cluster in four Aegilops tauschii accessions reveals multiple levels of conservation of genes and gene-sequence. All three genes are conserved in accessions TA1703 and TA2468. In contrast TA1704 contains CDSs 3 and 5 but is missing CDS7. Furthermore, TA1691 contains CDS3 and is missing CDSs 5 and 7, the loss of which may have occurred from a recombination event between group 1D and 7D chromosomes. Furthermore, DNA sequence analysis supports genetic evidence for a gene duplication event on 1DS involving CDS5 and the Lr21 gene. Therefore, chromosome rearrangements have dramatically altered gene content, resulting in deletion and duplication of telomeric genes of chromosome 1DS.