Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 14, 2001
Publication Date: N/A
Technical Abstract: The barley Mla locus confers gene-for-gene resistance to Blumeria graminis f. sp. hordei, the causal agent of powdery mildew disease. Using a single-cell transient assay, we have shown that the CC-NBS-LRR proteins encoded by the Mla6 and Mla13 alleles confer resistance to isolates of B. graminis that possess AvrMla6 and AvrMla13, respectively. The MLA6 and MLA13 proteins are 92% identical, but recognize different avirulence factors. To investigate the regions required for specificity, we have used the single-cell transient assay to test genes chimeric for the MLA6 and MLA13 LRRs. Mla6 and Mla13 both contain small upstream reading frames (SMURFs) within their 5' UTRs that may function in post-transcriptional regulation of protein expression. Deletion analysis of the 5 'UTRs coupled with the single-cell transient assay will determine whether these SMURFs have an important role in Mla-mediated resistance. An expressed, truncated dversion of Mla6, designated Mla6-2, was identified in our cDNA library screen. Mla6-2 encodes a small protein with only the coiled-coil domain when compared to wild-type Mla6. Closely related homologs of this gene have been isolated via PCR from numerous cultivars with different Mla specificities, including Mla1, Mla12 and Mla13. We have isolated cosmids containing Mla6-2 to test for function in the single-cell transient assay and to determine the position of Mla6-2 in the barley genome.