Plant Physiol, February 2003, Vol. 131, pp. 482-492
Sequence Analysis of a 282-Kilobase Region Surrounding the
Citrus Tristeza Virus Resistance Gene (Ctv) Locus in
Poncirus trifoliata L. Raf.1
Zhong-Nan
Yang,23
Xin-Rong
Ye,2
Joe
Molina,
Mikeal L.
Roose,* and
T. Erik
Mirkov*
Department of Plant Pathology and Microbiology, Agricultural
Experiment Station, Texas A&M University, Weslaco, Texas 78596 (Z.-N.Y., J.M., T.E.M.); and Department of Botany and Plant Sciences,
University of California, Riverside, California 92521 (X.-R.Y., M.L.R.)
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 8× 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.
1
This work was supported by the California Citrus
Research Board (grant no. CTV-009 to M.L.R.), by the U.S. Department
of Agriculture-Agricultural Research Service (grant no. 59-0790-8-51
to T.E.M. and M.L.R.), and by the U.S. Department of
Agriculture-Cooperative State Research, Education, and Extension
Service (grant nos. 99-34399-8460, 00-34399-9343, and
01-34399-10748 to T.E.M. and M.L.R.).
2
These authors contributed equally to the paper.
3
Present address: Department of Biology, Shanghai Normal
University, 100 Caobao Road, Shanghai, 200234, Peoples Republic of China.
*
Corresponding authors; e-mail roose{at}citrus.ucr.edu (M.L.R.)
or e-mirkov{at}tamu.edu (T.E.M.).; fax 909-787-4437 (M.L.R.) or
956-968-0641 (T.E.M.).
© 2003 American Society of Plant Biologists
