Characterization and cloning of TMV resistance gene N homologues from Nicotiana tabacum
Tobacco cultivars Nicotiana tabacum cv. Samsun NN plants carrying the N gene contain a multitude of N-related genes. We cloned a few N homologues and isolated two full-length cDNAs of NL-C26 and NL-B69 genes from N. tabacum cv. Samsun NN. Nucleotide sequence analysis showed that the coding regions of NL-C26 (3,498 bp) and NL-B69 (3,510 bp) had 86 and 83% nucleotide identities with the N gene, respectively. Amino acid sequence analysis revealed that NL-C26 and NL-B69 had the Toll-interleukin-1 receptor/nucleotide-binding site/leucine-rich repeat (TIR/NBS/LRR) structure with 78 and 73% identities to N, respectively. These result indicated that NL-C26 was more similar to N than NL-B69. Tobacco mosaic virus (TMV) infection experiments suggest that NL-C26 and NL-B69 could interact with distinct avirulence (Avr) proteins of yet unidentified pathogens and function as potential HR-inducing resistance proteins similar to N.
Key words: N gene, tobacco mosaic virus (TMV), N homologue, Nicotiana tabacum, hypersensitive response.