title: Sequence analysis of a 282-kilobase region surrounding the citrus Tristeza virus resistance gene (Ctv) locus in Poncirus trifoliata L. Raf.
abstract: Citrus tristeza virus (CTV) is the major virus pathogen causing significant economic damage to citrus worldwide, and a single dominant gene, Ctv, provides broad spectrum resistance to CTV in Poncirus trifoliata L. Raf. Ctv was physically mapped to a 282-kb region using a P. trifoliata bacterial artificial chromosome library. This region was completely sequenced to about 8x coverage using a shotgun sequencing strategy and primer walking for gap closure. Sequence analysis predicts 22 putative genes, two mutator-like transposons and eight retrotransposons. This sequence analysis also revealed some interesting features of this region of the P. trifoliata genome: a disease resistance gene cluster with seven members and eight retrotransposons clustered in a 125-kb gene-poor region. Comparative sequence analysis suggests that six genes in the Ctv region have significant sequence similarity with their orthologs in bacterial artificial chromosome clones F7H2 and F21T11 from Arabidopsis chromosome I. However, the analysis of gene colinearity between P. trifoliata and Arabidopsis indicates that Arabidopsis genome sequence information may be of limited use for positional gene cloning in P. trifoliata and citrus. Analysis of candidate genes for Ctv is also discussed.
authors.affiliation: Department of Plant Pathology, Agricultural Experiment Station, Texas A&M University, Weslaco, Texas 78596, USA.
authors.forename: Zhong-Nan
authors.initials: ZN
authors.lastname: Yang
authors.forename: Xin-Rong
authors.initials: XR
authors.lastname: Ye
authors.forename: Joe
authors.initials: J
authors.lastname: Molina
authors.forename: Mikeal L
authors.initials: ML
authors.lastname: Roose
authors.forename: T Erik
authors.initials: TE
authors.lastname: Mirkov
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics; D003001:Cloning, Molecular; D020451:Contig Mapping; D004251:DNA Transposable Elements / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D018745:Genome, Plant; D007113:Immunity, Innate / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics* / Q000821:virology; D010940:Plant Proteins / Q000235:genetics*; D010942:Plant Viruses / Q000254:growth & development*; D032104:Poncirus / Q000235:genetics* / Q000821:virology; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D026801:Synteny
chemical_list: D004251:DNA Transposable Elements; D018744:DNA, Plant; D010940:Plant Proteins; C474073:citrus Tristeza virus resistance protein, Poncirus trifoliata