Isolation and Characterization of Disease Resistance Gene Analogs from <I>Erianthus arundinaceus</I> cDNA

Abstract

Plant disease resistance genes (R-genes) encode some conserved motifs. According to the conserved motifs present in the known NBS-LRR R-gene sequences and R gene analogs (RGAs), several degenerate primers were designed and applied in the RGA isolation from Erianthus arundinaceus using PCR approach. In total, 6 RGAs were successfully obtained, with GenBank accession numbers of EU685835, EU685836, EU685837, EU685838, EU685839, and EU685840. Multiple alignments showed that the encoding sequences of the six clones were highly conserved and strikingly similar to the eleven most typical NBS-LRR type R-gene peptide sequences, especially at the four NES motifs of P-loop. kinase-2, kinase-3a, and HD. The identity percentage at the amino-acid level ranged from 8.3% to 93.0% among all 17 sequences tested and from 30.5% to 45.6% among the six RGAs cloned in this study. The results of cluster analysis and the existence of an aspartic acid residue (D) at the final residue position of the kinase-2 motif also indicated that all of E. arundinaceus RGAs might belong to non-TIR group. The Real-time PCR results showed that all of the RGAs were constitutively expressed in roots, stalks and leaves of E. arundinaceus, and their expression could be up-regulated in leaves by the exogenous signal molecules SA and H2O2. Therefore, it suggested that E. arundinaceus RGAs might play important roles in disease resistance in an SA- and H2O2-dependent defense response pathway. Further studies should aim to clone full-length R-genes in E. arundinaceus and characterize their functions in defense responses.