title: Cloning, structural features, and expression analysis of resistance  gene analogs in tobacco.
abstract: Using degenerate primers based on the conserved nucleotide binding site (NBS) and protein kinase domain (PKD), 100 resistance gene analogs (RGAs) were isolated from tobacco variety Nicotiana repanda. BLASTx search against the GenBank database revealed that 27 belong to the NBS class and 73 belong to the protein kinase (PK) class. Cluster analysis and multiple sequence alignment of the deduced protein sequences indicate that RGAs of the NBS class can be divided into two groups: toll/interleukin receptor (TIR) and non-TIR types. Both types possess 6 conserved motifs (P-loop, RNBS-A, Kinase-2, RNBS-B, RNBS-C, GLPL). Based on their sequence similarity, the tobacco RGAs of the PK class were assigned to 8 subclasses. We examined their expression after infection with either Tobacco mosaic virus (TMV) or the tobacco black shank pathogen (Phytophthora parasitica var. nicotianae). The expression levels of 4 RGAs of the PK class were significantly elevated by TMV and 1 RGA of the PK class and 3 RGAs of the NBS class were up-regulated by P. parasitica var. nicotianae. The expression of two RGAs of the PK class was induced by P. parasitica var. nicotianae. Infection by either TMV or P. parasitica var. nicotianae enhanced the expression of NtRGA2, a RGA of the PK class. The present study shows that RGAs are abundant in the tobacco genome and the identification of tobacco RGAs induced by pathogens should provide valuable information for cloning related resistance genes in tobacco.
authors.affiliation: Yunnan Academy of Tobacco Agricultural Science, Yuxi, China.
authors.forename: Yulong
authors.initials: Y
authors.lastname: Gao
authors.forename: Zhaoli
authors.initials: Z
authors.lastname: Xu
authors.forename: Fangchan
authors.initials: F
authors.lastname: Jiao
authors.forename: Haiqin
authors.initials: H
authors.lastname: Yu
authors.forename: Bingguang
authors.initials: B
authors.lastname: Xiao
authors.forename: Yongping
authors.initials: Y
authors.lastname: Li
authors.forename: Xiuping
authors.initials: X
authors.lastname: Lu
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics*; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics; D011494:Protein Kinases / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D014026:Nicotiana / Q000201:enzymology / Q000235:genetics* / Q000276:immunology*
chemical_list: D009711:Nucleotides; D010940:Plant Proteins; D011494:Protein Kinases