Diversity of NBS-LRR disease-resistance gene analogs in Hevea brasiliensis.

【Objective】 The present study aimed to clone the nucleotide binding site(NBS) type resistance gene analogs(RGAs) in Hevea brasiliensis in order to provide references for acquisition of resistance genes(R genes).【Method】 The resistance gene analogs were cloned from the cDNA of leaf by SA induction for respective 0,12,24,48 h using a pair of specific degenerated primers based on the conserved regions of NBS-leucine rich repeat(LRR) domain of plant R genes.【Result】 Sequence analysis showed that the cloned Hevea brasiliensis RGAs belonged to the non-TIR-NBS-LRR and TIR-NBS-LRR type and 9 gene families.Through multiple comparisons,the cloned RGAs had typical conservative domain of NBS.Compared with known NBS sequence,RGAs had similarity rate of 46.2% with I2c-2 gene,while amino acid similarity amongst RGAs in Hevea brasiliensis NBS reached 22.1%-100.0%.Further studies revealed the ds/dn ratio was less than 1 indicating a low level of recombination.NBS analogs in Hevea brasiliensis were subject to gradual accumulation of mutations which was the major force leading to purifying selection.【Conclusion】 Obtained from SA induction and resistance gene NBS,the cloned RGAs had wide heredity diversity and high similarity with amino acid sequence in known resistance gene.Those candidate resistance gene sequences may be closely related to a resistance gene in Hevea brasiliensis.