title: The broad-spectrum blast resistance gene Pi9 encodes a nucleotide-binding site-leucine-rich repeat protein and is a member of a multigene family in rice.
abstract: The broad-spectrum rice blast resistance gene Pi9 was cloned using a map-based cloning strategy. Sequencing of a 76-kb bacterial artificial chromosome (BAC) contig spanning the Pi9 locus led to identification of six tandemly arranged resistance-like genes with a nucleotide-binding site (NBS) and leucine-rich repeats (LRRs) (Nbs1-Pi9-Nbs6-Pi9). Analysis of selected Pi9 deletion mutants and transformation of a 45-kb fragment from the BAC contig into the susceptible rice cultivar TP309 narrowed down Pi9 to the candidate genes Nbs2-Pi9 and Nbs3-Pi9. Disease evaluation of the transgenic lines carrying the individual candidate genes confirmed that Nbs2-Pi9 is the Pi9 gene. Sequence comparison analysis revealed that the six paralogs at the Pi9 locus belong to four classes and gene duplication might be one of the major evolutionary forces contributing to the formation of the NBS-LRR gene cluster. Semiquantitative reverse transcriptase (RT)-PCR analysis showed that Pi9 was constitutively expressed in the Pi9-resistant plants and was not induced by blast infection. The cloned Pi9 gene provides a starting point to elucidate the molecular basis of the broad-spectrum disease resistance and the evolutionary mechanisms of blast resistance gene clusters in rice.
authors.affiliation: Department of Plant Pathology, Ohio State University, Columbus 43210, USA.
authors.forename: Shaohong
authors.initials: S
authors.lastname: Qu
authors.forename: Guifu
authors.initials: G
authors.lastname: Liu
authors.forename: Bo
authors.initials: B
authors.lastname: Zhou
authors.forename: Maria
authors.initials: M
authors.lastname: Bellizzi
authors.forename: Lirong
authors.initials: L
authors.lastname: Zeng
authors.forename: Liangying
authors.initials: L
authors.lastname: Dai
authors.forename: Bin
authors.initials: B
authors.lastname: Han
authors.forename: Guo-Liang
authors.initials: GL
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D020440:Gene Duplication; D017343:Genes, Plant / Q000235:genetics*; D007930:Leucine / Q000235:genetics* / Q000378:metabolism*; D020082:Magnaporthe / Q000472:pathogenicity; D008969:Molecular Sequence Data; D005810:Multigene Family; D009711:Nucleotides / Q000235:genetics / Q000378:metabolism*; D012275:Oryza / Q000235:genetics* / Q000382:microbiology; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology*; D010940:Plant Proteins / Q000235:genetics; D030821:Plants, Genetically Modified / Q000235:genetics; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion
chemical_list: D009711:Nucleotides; D010940:Plant Proteins; D007930:Leucine