Submitted to: Plant and Animal Genome Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/16/2003
Publication Date: 1/16/2003
Citation: HALTERMAN, D.A., WISE, R.P. MLA RESISTANCE SPECIFICITIES ARE NOT LINEAR DESCENDANTS OF A COMMON ANCESTOR, BUT EVOLVED SEPARATELY SUBSEQUENT TO GENE DUPLICATION. AVAILABLE FROM: http://www.intl-pag.org/11/abstracts/P7b_P828_XI.html. PLANT AND ANIMAL GENOME CONFERENCE PROCEEDINGS. 2003. ABSTRACT NO. P828.
Technical Abstract: The Mla locus of barley confers gene-for-gene resistance to Blumeria graminis f. sp. hordei (Bgh). Up to 30 different resistance specificities have been identified at Mla. The 261-kb Mla-spanning sequence in cv. Morex contains families of resistance gene homologs, RGH1, 2, and 3. The Morex RGHs, as well as the cloned Mla genes, Mla1, Mla6, and Mla13, all encode coiled-coil, nucleotide-binding site, leucine-rich repeat (CC-NBS-LRR) resistance proteins. Using genomic sequence flanking these genes and the related Mla13-2, Mla1-2, and the transcriptionally active Mla6-2 genes, we examined the micro-evolution of Mla. While all of the characterized Mla genes are most similar to the RGH1 family, the presence or absence of common retroelements flanking these genes has revealed that they are likely not direct linear descendants of a common ancestor. Our analysis shows that at least two different paralogs of Mla are responsible for the functional diversity within the locus. The similarity within the open reading frames of Mla genes has facilitated rtPCR amplification of previously uncharacterized Ml genes from various barley varieties. While most varieties express one gene with high similarity to Mla, others appear to express additional Mla homologs containing deletions or insertions. Our investigation of the genomic sequence flanking each of the characterized Mla genes and the coding regions of Ml genes not yet identified will help in our understanding of how powdery mildew resistance in barley has evolved.