Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/14/2001
Publication Date: N/A
Technical Abstract: The barley Mla (powdery mildew) resistance cluster contains one of the highest degrees of variability among all plant-disease resistance loci. The primary structure of the 261-kb barley Mla region encompasses thirty-two protein-encoding genes and two tRNApro genes. Notably, sixteen of these genes are plant-defense related; 12 of these 16 are associated with defense against powdery mildew disease, but function in different signaling pathways. These defense related and other protein-encoding sequences are organized as three gene-rich islands separated by two 40-kb complexes of nested transposons and a gene-poor region. Our results indicate that defense-related genes tend to cluster together and that the present Mla region evolved over a period of approximately 7 million years through a series of duplication and inversion events in addition to nested transposable element insertion. We present a model for the evolution of the Mla region, which reveals some emerging features of large cereal genomes.