Molecular cloning, characterization, and expression analysis of resistance gene candidates in Kaempferia galanga L

Majority of the plant disease resistance genes expresses cytoplasmic receptor-like proteins characterized by an N-terminal nucleotide-binding site (NBS) and a leucine-rich repeat (LRR) domain. Degenerative primers based on these conserved motifs were used to isolate NBS type sequences in Kaempferia galanga. Cloning and sequencing identified 12 Kaempferia NBS-type sequences called resistance gene candidates (RGCs) classified into four classes. The amino acid sequences of the RGCs detected the presence of conserved domains, viz., kinase-1a, kinase-2, and hydrophobic GLPL, categorizing them with the NBS-LRR class gene family. Structural and phylogenetic characterization grouped the RGCs with the non-toll interleukin receptor (non-TIR) subclasses of the NBS sequences. Reverse transcription PCR with 10 Kaempferia RGC specific primers revealed 7 out of 10 Kaempferia RGCs to be expressive. The isolation and characterization of Kaempferia RGCs has been reported for the first time in this study. This will provide a starting point towards characterization of candidate resistance genes in Kaempferia and can act as a source pool for disease resistance development in other asexually reproducing plants.