Abstract:

According to the conservative region of resistance gene homologue (RGH) family of the barley Mla locus, we synthesized four pairs of family primers. RT-PCR with the series of family-specific primers was used to analyze the differential expression of genes between the inoculated seedlings and the uninoculated seedlings of a wheat (Triticum aestivum L.) line which showed high resistance to powdery mildew. As a result, a putative resistance gene fragment, RJ-3-3L, expressed specifically in the inoculated condition, was isolated and then, its full-length cDNA, designated as TaMla1, was obtained using rapid amplification of cDNA ends (RACE). By alignment analysis and functional-motif scanning, the TaMla1 shared high similarity to Mla alleles in barley and coded a typical CC-NBS-LRR (coiled-coil, nucleotide binding site, Leu-rich repeat) resistance protein. Subsequently, by Southern blot using a series of nulli-tetrasomics of wheat, the TaMla1 was located on wheat chromosome 1A, where the ortholog of the barley Mla locus lies. These findings showed that TaMla1 is one of the Mla-like alleles in wheat. In addition, another gene fragment, RW-2-3L, its transcription remarkably inhibited in the inoculated seedlings, was isolated and homology analysis showed that it was also highly similar to Mla members in barley. We inferred that the gene derived RW-2-3L was also a Mla-like allele and probably acted as a powdery mildew susceptible gene or a negative factor for resistance to powdery mildew.

Key words: wheat, Mla-like gene, resistance to powdery mildew, negative or susceptible factor