Genomic DNA sequences sharing homology with NBS region of resistance
gene analogs were isolated and characterized from Pongamia glabra ,
Adenanthera pavonina , Clitoria ternatea and Solanum trilobatum
using PCR based approach with primers designed from conserved regions
of NBS domain. The presence of consensus motifs viz., kinase 1a, kinase
2, kinase 3a and hydrophobic domain provided evidence that the cloned
sequences may belong to the NBS-LRR gene family. Conservation of
tryptophan as the last residue of kinase-2 motif further confirms their
position in non-TIR NBS-LRR family of resistance genes. The Resistance
Gene Analogs (RGAs) cloned from P. glabra, A. pavonina, C. ternatea and
S. trilobatum clustered together with well- characterized
non-TIR-NBS-LRR genes leaving the TIR-NBS-LRR genes as a separate
cluster in the average distance tree constructed based on BLOSUM62. All
the four RGAs had high level of identity with NBS-LRR family of RGAs
deposited in the GenBank. The extent of identity between the sequences
at NBS region varied from 29% (P. glabra and S. trilobatum) to 78% (A.
pavonina and C. ternatea), which indicates the diversity among the
RGAs