Isolation, characterisation and phylogenetic analysis of resistance gene analogues in a wild species of peach (Prunus kansuensis)

Abstract

Cao, K., Wang, L. R., Zhu, G. R., Fang, W. CH. and Chen, CH. W. 2011. Isolation, characterisation and phylogenetic analysis of resistance gene analogues in a wild species of peach ( Prunus kansuensis ). Can. J. Plant Sci. 91: 961–970. Conserved motifs, such as nucleotide binding site (NBS) and leucine-rich repeat (LRR) domains, have been found in resistance (R) genes cloned from plant species. These allow the study of plant defence mechanisms and isolating candidate genes in several species including peaches. Seventy-five resistance gene analogues (RGA) were identified using two different degenerative primer pairs in the Honggengansutao (Prunus kansuensis), a wild species of peach resistant to drought and nematodes. Through aligning their amino-acid sequences, P-loop and GLPL motifs were found in 48 RGAs with open-reading frames (ORF). These RGAs and 17 RGAs from Arabidopsis thaliana, Capsicum annuum and Solanum lycopersicum were grouped into two classes by phylogenetic analysis: toll and interleukin-1 receptor (TIR)- and non-TIR-NBS. Most Honggengansutao RGAs were TIR-NBS. A semiquantitative RT-PCR analysis revealed transcript-level variations of 22 RGAs in the young leaves, flowers, fruits and roots of the Honggengansutao, demonstrating their probable role in resistance against diseases attacking the organs. This is the first large-scale analysis of NBS-LRR RGAs in P. kansuensis, this technique has the potential for involvement in rootstock breeding. It will foster further R gene isolation and exploitation.