Plant proteins

Abstract

The present invention is based on the isolation and characterization of a plant cell DNA sequence encoding for a retinoblastoma protein. Such finding is based on the structural and functional properties of the plant retinoblastoma protein as possible regulator of the cellular cycle, of the cellular growth and of the plant cellular differentiation. For this reason, among other aspects, it is claimed the use of retinoblastoma protein or the DNA sequence which encodes for it in the growing control of vegetable cells, plants and/or vegetable virus, as well as the use of vectors, cells, plants or animals, or animal cells modified through the manipulation of the control route based on plant retinoblastoma protein.

1 . A method of controlling the growth of a plant cell or a plant virus within that cell comprising increasing or decreasing the level and/or activity of retinoblastoma protein in that plant cell by incorporation therein of a recombinant nucleic acid.  
     
     
         2 . A method as claimed in  claim 1  characterised in that the nucleic acid is such as to increase or inhibit expression of a retinoblastoma protein in the cell.  
     
     
         3 . A method as claimed in  claim 1  characterised in that the nucleic acid is such as to express a retinoblastoma protein or peptide fragment of a retinoblastoma protein that interacts with viral LXCXE motif without affecting the normal functioning of the cell.  
     
     
         4 . A method as claimed in  claim 3  characterised in that the retinoblastoma protein has been rendered resistant to phosphorylation by cyclin dependent kinases by change or deletion of one or more consensus SP or TP sites found in the SEQ ID No. 2.  
     
     
         5 . A method as claimed in  claim 2  characterised in that the DNA or RNA is antisense to retinoblastoma protein encoding DWA or RNA and inhibits retinoblastoma protein expression.  
     
     
         6 . A method of transforming a plant cell such that it is directed into the S phase of the cell cycle comprising introducing a nucleic acid encoding antisense RNA to a plant retinoblastoma protein.  
     
     
         7 . Recombinant nucleic acid encoding for expression of a retinoblastoma protein characterised in that the retinoblastoma protein has an amino acid sequence having 80% or more homology with that of SEQ No. 2 of the sequence listing attached hereto.  
     
     
         8 . Recombinant nucleic acid as claimed in  claim 7  characterised in that it comprises SEQ ID no. 1, bases 31-207, sequences only having degenerate substitutions thereof or sequences capable of hybridizing with a polynucleotide of SEQ ID No. 1 under conditions of high stringency.  
     
     
         9 . Recombinant nucleic acid as claimed in  claim 7  or  8  characterised in that it encodes for a retinoblastoma protein conservatively substituted with respect to SEQ ID No. 2.  
     
     
         10 . Recombinant nucleic acid characterised in that it comprises antisense DNA or RNA to a plant retinoblastoma protein.  
     
     
         11 . Recombinant nucleic acid as claimed in  claim 10  characterised in that it comprises antisense DNA or RNA to a plant retinoblastoma protein comprising SEQ ID No. 2 or a sequence having at least 80% homology thereto.  
     
     
         12 . Recombinant nucleic acid as claimed in  claim 10  or  11  characterised in that it comprises antisense DNA or RNA to that of SEQ ID No. 1 or a sequence having at least 80% homology thereto.  
     
     
         13 . Recombinant nucleic acid characterised in that it encodes for a retinoblastoma protein or a peptide fragment of a retinoblastoma protein that interacts with viral LXCXE motif without affecting the normal functioning of a plant cell.  
     
     
         14 . Recombinant nucleic acid as claimed in  claim 13  characterised in that it encodes for a plant retinoblastoma protein in which one or more consensus SP or TP sites found in the SEQ ID No. 2 have been changed or deleted.  
     
     
         15 . A protein produced by the expression of a recombinant DNA or RNA as claimed in any one of  claims 7  to  9 ,  13  and  14 .  
     
     
         16 . A protein as claimed in  claim 15  characterised in that one or more consensus SP or TP sites found in the SEQ ID No. 2 have been changed or deleted.  
     
     
         17 . A recombinant vector characterised in that it comprises a recombinant nucleic acid as claimed in any one of  claims 7  to  9 ,  13  and  14 .  
     
     
         18 . A plant cell characterised in that it comprises a recombinant nucleic acid encoding for expression of a retinoblastoma protein.  
     
     
         19 . A plant cell as claimed in  claim 18  characterised in that it comprises a recombinant nucleic acid as claimed in any one of  claims 7  to  9 ,  13  and  14 .  
     
     
         20 . A plant cell as claimed in  claim 18  or  19  characterised in that it expresses a retinoblastoma protein from said nucleic acid.  
     
     
         21 . A transgenic plant characterised in that it comprises a cell as claimed in any one of  claims 18  to  20 .