Citrus tristeza virus resistance genes and methods of use

Abstract

Nucleic acid molecules Rcan5 and Rcan6 derived from Poncirus confer disease resistance to citrus tristeza virus (CTV) infection in a non-Poncirus plant. Methods of conferring disease resistance to CTV infection, as well as citrus plants having a nucleic acid molecule that induces disease resistance to CTV infection are described.

1 . A purified nucleic acid isolatable from  Poncirus trifoliata , the nucleic acid having the ability to confer resistance in a plant cell to pathology caused by CTV infection when the nucleic acid is present in the plant cell.  
     
     
         2 . The purified nucleic acid of  claim 1 , wherein the nucleic acid is a purified Rcan6 gene.  
     
     
         3 . The purified nucleic acid of  claim 1 , wherein the nucleic acid comprises a nucleotide sequence that encodes a protein (a) that has at least 65% sequence identity to the amino acid sequence of SEQ ID NO:15 and (b) has at least one functional activity of native RCAN6.  
     
     
         4 . The purified nucleic acid of  claim 1 , wherein the nucleic acid comprises a nucleotide sequence that encodes a protein (a) that has at least 75% sequence identity to the amino acid sequence of SEQ ID NO:15 and (b) has at least one functional activity of native RCAN6.  
     
     
         5 . The purified nucleic acid of  claim 1 , wherein the nucleic acid comprises a nucleotide sequence that encodes a protein (a) that has at least 85% sequence identity to the amino acid sequence of SEQ ID NO:15 and (b) has at least one functional activity of native RCAN6.  
     
     
         6 . The purified nucleic acid of  claim 1 , wherein the nucleic acid comprises a nucleotide sequence that encodes a protein (a) that has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:15 and (b) has at least one functional activity of native RCAN6.  
     
     
         7 . The purified nucleic acid of  claim 1 , wherein the nucleic acid comprises a nucleotide sequence that encodes a protein (a) that comprises the amino acid sequence of SEQ ID NO:15 and (b) has at least one functional activity of native RCAN6.  
     
     
         8 . The nucleic acid of  claim 1 , wherein the nucleic acid comprises the nucleotide sequence of SEQ ID NO:14.  
     
     
         9 . The nucleic acid of  claim 1 , wherein the nucleotide sequence defines a polynucleotide whose complement hybridizes under high stringency conditions to the nucleotide sequence of SEQ ID NO:14.  
     
     
         10 . A vector comprising the nucleic acid of  claim 1 .  
     
     
         11 . The vector of  claim 10 , wherein said nucleic acid is operably linked to one or more expression control sequences.  
     
     
         12 . A cell or seed comprising the nucleic acid of  claim 1 .  
     
     
         13 . A purified protein that comprises an amino acid sequence that shares at least 80% sequence identity with SEQ ID NOs:13 or 15.  
     
     
         14 . The protein of  claim 13  whose amino acid sequence is SEQ ID NOs:13 or 15.  
     
     
         15 . The protein of  claim 13 , wherein the protein is a fused heterologous polypeptide.  
     
     
         16 . A purified antibody that specifically binds to the protein of  claim 13 .  
     
     
         17 . The antibody of  claim 16 , further comprising a detectable label.  
     
     
         18 . A plant into which has been introduced the nucleic acid of  claim 1 .  
     
     
         19 . The plant of  claim 18 , wherein the plant is of the genus  Citrus.    
     
     
         20 . The plant of  claim 18 , wherein the plant is selected from the group consisting of: sweet oranges, grapefruits, mandarins, tangerines, pumelos, lemons, limes and citrons.  
     
     
         21 . The plant of  claim 18 , wherein the plant comprises  citrus  scion and a rootstock cultivar.  
     
     
         22 . The plant of  claim 18 , wherein the plant comprises a rootstock cultivar selected from the group consisting of: sour orange, rough lemon, mandarin and  citrus.    
     
     
         23 . The plant of  claim 21 , wherein the rootstock cultivar comprises a  citrus  intrageneric hybrid.  
     
     
         24 . The plant of  claim 21 , wherein the rootstock cultivar comprises a  citrus  intergeneric hybrid.  
     
     
         25 . The plant of  claim 18 , wherein the plant is an intrageneric hybrid, including tangelos and tangors.  
     
     
         26 . The plant of  claim 18 , wherein the plant comprises a breeding line.  
     
     
         27 . The plant of  claim 18 , wherein the plant is a  Fortunella  species, including calamondin and kumquat.  
     
     
         28 . The plant of  claim 18 , wherein the nucleic acid comprises a selectable marker.  
     
     
         29 . The plant of  claim 28 , wherein the selectable marker is selected from the group consisting of: antibiotic resistance gene(s), β-glucuronidase gene (GUS), and nucleotide sequence encoding green fluorescent protein (GFP).  
     
     
         30 . A method of imparting disease resistance in a plant, plant cell or plant seed, the method comprising the steps of: 
 (A) providing a plant, plant cell or plant seed; and    (B) introducing into the plant, plant cell or plant seed the purified nucleic acid of  claim 1 .    
     
     
         31 . The method of  claim 30 , wherein the purified nucleic acid further comprises a selectable marker.  
     
     
         32 . The method of  claim 31 , wherein the selectable marker is selected from the group consisting of: antibiotic resistance gene(s), beta-glucuronidase gene (GUS) and nucleotide sequence encoding GFP.  
     
     
         33 . The method of  claim 30 , wherein the step (B) of introducing into the plant, plant cell or plant seed the purified nucleic acid comprises incorporating the purified nucleic acid into a suitable expression erector.  
     
     
         34 . The method of  claim 30 , wherein the step (B) of introducing into the plant, plant cell or plant seed a purified nucleic acid comprises transforming the plant, plant cell or plant seed with an  Agrobacterium  strain.  
     
     
         35 . The method of  claim 30 , wherein the step (B) of introducing into the plant, plant cell or plant seed a purified nucleic acid comprises microprojectile bombardment.  
     
     
         36 . The method of  claim 30 , wherein the step (B) of introducing into the plant, plant cell or plant seed a purified nucleic acid comprises direct nucleic acid uptake by protoplasts.