Conserved domains e.g. nucleotide binding site (NBS) were found in several cloned plant disease resistance genes. Based on the NBS domain, resistance gene analogs (RGAs) have been isolated previously and were used as probes to screen a soybean (
Glycine max
L. Merr.) cDNA library. A full-length cDNA,
KR3, was obtained by screening the library and rapid amplification of cDNA ends (RACE) method. Sequence analysis revealed that the cDNA is 2 353 bp in length and the open reading frame (ORF) codes for a polypeptide of 636 amino acids with a Toll-Interleukin-1 receptor (TIR) and a NBS domain. Sequence alignment showed that it was similar to
N gene of tobacco. The phylogenetic tree analysis of R proteins with NBS from higher plants was performed. The
KR3 gene has low copies in soybean genome and its expression was induced by exogenous salicylic acid (SA).
