Geminivirus resistant transgenic plants

Abstract

Transgenic plants with increased resistance to geminivirus infection, and nucleic acid constructs useful in producing such plants, are described. The transgenic plants express a mutant AL3/C3 geminivirus protein, which increases resistance to infection by at least one geminivirus, compared to a non-transformed control plant.

What is claimed is:  
     
         1 . A plant comprising transformed plant cells, said transformed plant cells containing a heterologous nucleic acid construct comprising, in the 5′ to 3′ direction: 
 (a) a promoter operable in said plant cells,  
 (b) a nucleic acid sequence encoding a mutant AL3/C3 protein, said nucleic acid sequence located downstream from said promoter and operatively associated therewith, and  
 (c) a termination sequence positioned downstream from said nucleic acid sequence and operatively associated therewith,  
 wherein expression of said mutant AL3/C3 protein increases resistance of said plant to infection by at least one geminivirus, compared to a non-transformed control.  
 
     
     
         2 . A plant according to  claim 1 , wherein said plant has increased resistance to a geminivirus selected from the group consisting of tomato golden mosaic virus, tomato mottle virus, tomato yellow leaf curl virus, tomato leaf curl virus, African cassava mosaic virus, Indian cassava mosaic virus, potato yellow mosaic virus, bean golden mosaic virus, bean dwarf mosaic virus, squash leaf curl virus, Texas pepper virus, cotton leaf curl virus and beet curly top virus.  
     
     
         3 . A plant according to  claim 1 , which promoter is constitutively active in said plant.  
     
     
         4 . A plant according to  claim 1 , which plant is selected from the group consisting of tomato, cassava, potato, bean, squash and beet.  
     
     
         5 . A tomato plant comprising transformed tomato plant cells, said transformed tomato plant cells containing a heterologous nucleic acid construct comprising, in the 5′ to 3′ direction: 
 (a) a promoter operable in said plant cells,  
 (b) a nucleic acid sequence encoding a mutant AL3/C3 protein, said nucleic acid sequence located downstream from said promoter and operatively associated therewith, and  
 (c) a termination sequence positioned downstream from said nucleic acid sequence and operatively associated therewith,  
 wherein expression of said mutant AL3/C3 protein increases resistance of said tomato plant to infection by at least one geminivirus, compared to a non-transformed control.  
 
     
     
         6 . A tomato plant according to  claim 5 , wherein said tomato plant has increased resistance to a geminivirus selected from the group consisting of tomato golden mosaic virus, tomato mottle virus, tomato yellow leaf curl virus and tomato leaf curl virus.  
     
     
         7 . A plant of the family Solanaceae, wherein cells of said plant are transformed to contain a heterologous nucleic acid construct comprising, in the 5′ to 3′ direction: 
 (a) a promoter operable in said plant cells,  
 (b) a nucleic acid sequence encoding a mutant AL3/C3 protein, said nucleic acid sequence located downstream from said promoter and operatively associated therewith, and  
 (c) a termination sequence positioned downstream from said nucleic acid sequence and operatively associated therewith,  
 wherein expression of said mutant AL3/C3 protein increases resistance of said plant to infection by at least one geminivirus, compared to a non-transformed control.  
 
     
     
         8 . A method of combating geminivirus infection in an agricultural field, comprising planting the field with a crop of plants comprising transformed plant cells, said transformed plant cells containing a heterologous nucleic acid construct comprising, in the 5′ to 3′ direction: 
 (a) a promoter operable in said plant cells,  
 (b) a nucleic acid sequence encoding a mutant AL3/C3 protein, said nucleic acid sequence located downstream from said promoter and operatively associated therewith, and  
 (c) a termination sequence positioned downstream from said nucleic acid sequence and operatively associated therewith,  
 wherein expression of said mutant AL3/C3 protein increases resistance of said plants to infection by at least one geminivirus, compared to a non-transformed control.  
 
     
     
         9 . A method of making a transgenic plant having increased resistance to geminivirus infection, said method comprising: 
 providing a plant cell capable of regeneration;    transforming said plant cell with a DNA construct comprising, in the 5′ to 3′ direction, a promoter operable in said plant cell, a nucleic acid sequence encoding a mutant AL3/C3 protein, said nucleic acid sequence located downstream from said promoter and operatively associated therewith, and a termination sequence positioned downstream from said nucleic acid sequence and operatively associated therewith; and then    regenerating a transgenic geminivirus-resistant plant from said transformed plant cell, wherein expression of said mutant AL3/C3 protein increases resistance of said plant to infection by at least one geminivirus, compared to a non-transformed control.    
     
     
         10 . A method according to  claim 9 , wherein said plant cell resides in a plant tissue capable of regeneration.  
     
     
         11 . A method according to  claim 9 , wherein said transforming step is carried out by bombarding said plant cell with microparticles carrying said expression cassette.  
     
     
         12 . A method according to  claim 9 , wherein said transforming step is carried out by infecting said cells with an  Agrobacterium tumefaciens  containing a Ti plasmid carrying said expression cassette.  
     
     
         13 . A nucleic acid construct comprising an expression cassette, which construct comprises, in the 5′ to 3′ direction: 
 (a) a promoter operable in a plant cell,  
 (b) a nucleic acid sequence encoding a mutant AL3/C3 protein, said nucleic acid sequence located downstream from said promoter and operatively associated therewith, and  
 (c) a termination sequence positioned downstream from said nucleic acid sequence and operatively associated therewith.  
 
     
     
         14 . A DNA construct according to  claim 13  carried by a plant transformation vector.  
     
     
         15 . A method of producing nucleic acid constructs useful in conferring increased geminivirus-resistance to plants, comprising: 
 a) identifying mutants of a geminivirus AL3/C3 protein that enhance geminivirus resistance in plant cells when expressed therein;    b) preparing a nucleic acid construct comprising, in the 5′ to 3′ direction, a promoter operable in a plant cell, a nucleic acid sequence encoding said mutant AL3/C3 protein, said nucleic acid sequence located downstream from said promoter and operatively associated therewith, and a termination sequence positioned downstream from said nucleic acid sequence and operatively associated therewith.    
     
     
         16 . Seed or progeny of a plant according to  claim 1 , which seed or progeny has inherited said nucleic acid sequence encoding a mutant AL3/C3 protein.  
     
     
         17 . Seed or progeny of a plant according to  claim 5 , which seed or progeny has inherited said nucleic acid sequence encoding a mutant AL3/C3 protein.  
     
     
         18 . Seed or progeny of a plant according to  claim 7 , which seed or progeny has inherited said nucleic acid sequence encoding a mutant AL3/C3 protein.