ABSTRACT

The NBS, LRR and kinase domain are the characteristic features of many plant resistance genes products. The NBS domain has many conserved amino acid sequences among different R genes. NBS domain was analysed in the present study on castor using degenerate primers designed to the conserved region after PCR amplification. The PCR amplified DNA fragments were cloned. Of the 120 clones obtained, 21 clones were sequenced and 8 of them showed significant sequence homology with the known R genes and resistance gene analogs isolated from other dicots and monocots at nucleotide and amino acid level on BLAST search. Two classes were identified among isolated castor RGCs using CLUSTAL W by multiple alignment. When compared with the known R genes of Arabidopsis and Lettuce, castor RCRGCs showed sequence similarity with RPS2 and RPM1 indicating the similarity in the leucine zipper region. An amino acid signature in the conserved motifs comprising the NBS domain clearly shows the distinction between the two classes. All the castor RGCs belongs to the class of R genes with LRR domain in the NBS region but not TIR domain.