A wheat disease resistance gene analog of the NBS-LRR class: identification and analysis

The objective of this work was to obtain a resistance gene analog from the TcLr35 wheat line. The 5' and 3' ends of the resistance gene homology fragment S2A2 from TcLr35 were obtained by rapid amplification cDNA ends (RACE), and a 3476-bp full length cDNA was obtained using gene specific primers based on the spliced sequence. Its deduced 866 amino acid sequence has the characteristic NBS-LRR domains of plant resistance gene products and includes a coiled-coil (CC) region typical of monocots. The genomic DNA sequence shows the presence of three exons and two short introns upstream of the predicted stop codon. BLASTp analysis indicates a considerable identity of S2A2 with a cloned barley NBS-LRR resistance gene homology sequence and a lower similarity with wheat leaf rust resistance genes Lr1, Lr21, Lr34, and Lr10. The S2A2 gene appeared not to be induced by Puccinia triticina and was a constitutive gene with low abundance in the wheat leaf tissue by semi-quantitative RT-PCR analysis.