Isolation and characterization of the N family of resistance genes [abstract]
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The N gene is a virus resistance gene found in the genome of Nicotiana glutinosa, which confers resistance to tobacco mosaic virus (TMV), among many other plant diseases. It is characteristic of a family of plant receptors that contain an N-terminal nucleotide-binding site (NBS) and a C-terminal leucine-rich repeat (LRR) which recognize and defend against attack by plant pathogens. Recently, a gene silencing assay has found that a second N. glutinosa resistance gene is responsible for targeting tombusviruses, such as tomato bushy stunt virus (TBSV), and is also closely related to the N gene. In order to identify and clone the TBSV resistance gene, NBS-LRR genes that are closely related to the N gene are being characterized. A previous PCR-based assay coupled with nucleotide sequencing indicated that the N-family of resistance genes consists of approximately 15 members. Currently, N homologs are being physically isolated from a N. glutinosa bacterial artificial chromosome (BAC) library. The N. glutinosa BAC library was probed with a portion of Exon1 of the N gene and to date, 13 BAC clones have been isolated. Portions of the N gene present on each of the BAC clones are being sequenced in an effort to further characterize the members of the N family of resistance genes.