Genome scanning for identification of resistance gene analogs (RGAs) in a highly durable blast resistance rice (Oryza sativa L.) cultivar, Moroberekan

Disease resistance in plants is a desirable economic trait. Many disease resistance genes from various plants have been cloned so far. The gene products of some of these can be distinguished by the presence of an N terminal nucleotide binding site and a C-terminal stretch of leucine-rich repeats. Oligonucleotides already designed from sequence motifs conserved between resistance N genes of tobacco and RPS2 of Arabidopsis thaliana were used as PCR primers (AS1/S2) to scan the rice blast disease resistant moroberekan genomic DNA. The primer pairs RL, CL and tobacco N gene which were used based on leucine-rich repeat regions of genes RPS2 in Arabidopsis, Cf9 of tomato against Cladosporium fulvum and N gene of tobacco confers resistance to the viral pathogen, tobacco mosaic virus respectively. The fragment amplified by the primer AS1/S2 was cloned and sequenced. The PCR products for the other three primers were sequenced directly. Homology search of the resultant nucleotide sequences and deduced amino acid sequences with the reported sequences available in public data bases of NCBI BLASTn and PSI blast indicated the presence of resistance protein-like gene in BRGA-1(blast resistant gene analogue-1), putative retro-elements and putative retro-transposons proteins in BRGA-2, mitochondrial DNA in BRGA-3 and NBS-LRR type resistance protein and NB-ARC domain containing expressed protein of Oryza sativa in BRGA-4.