Method for improving stem volume growth and biomass production in trees

Abstract

The present invention relates to a genetic construct comprising a nucleic acid sequence encoding cytokinin biosynthetic isopentenyl-transferase enzyme (IPT) operable linked to a promoter allowing expression of said nucleic acid sequence in cambial cells. The invention relates also a method for producing a transgenic plant capable of increased biomass production and/or increased stem volume growth compared to wild type plant and a method for improving the production of biomass and/or increased stem volume growth in trees, as well as to a tree that over expresses an endogenous or exogenous nucleic acid sequence encoding IPT in cambial cells and a wood product obtainable from the transgenic tree.

1 . A genetic construct comprising a first nucleic acid sequence (effector) encoding cytokinin biosynthetic isopentenyl-transferase enzyme operable linked to a second nucleic acid sequence (promoter) allowing expression of said first nucleic acid sequence in cambial cells, said first nucleic acid sequence being selected from the group of
 a) a nucleic acid sequence comprising SEQ ID NO:1;   b) a nucleic acid sequence encoding SEQ ID NO:2;   c) a nucleic acid sequence encoding an amino acid sequence comprising a conserved domain area A, B and/or C having an amino acid sequence selected from the group of SEQ ID NO:3, 4 and 5,   d) a nucleic acid sequence encoding an amino acid sequence comprising an area D having at least 80% identity to amino acid sequence SEQ ID NO:6;   e) a nucleic acid sequence encoding an amino acid sequence showing at least 80% identity to SEQ ID NO: 2; and   f) a nucleic acid sequence encoding an enzyme belonging to enzyme class EC 2.5.1.27.   
     
     
         2 . The genetic construct according to  claim 1 , wherein said first nucleic acid sequence encodes adenosine phosphate-isopentenyltransferase enzyme 7, IPT7. 
     
     
         3 . The genetic construct according to  claim 1 , wherein said first nucleic acid sequence is derived from  Arabidopsis.    
     
     
         4 . The genetic construct according to  claim 1 , wherein said second nucleic acid sequence is birch meristem promoter pBpCRE1, preferably defined by SEQ ID NO: 7. 
     
     
         5 . The genetic construct according to  claim 1 , wherein said second nucleic acid sequence is a cambial specific promoter. 
     
     
         6 . The genetic construct according to  claim 5 , wherein said promoter is  Populus  cambial specific promoter pLM5. 
     
     
         7 . A vector comprising the genetic construct according to  claim 1 . 
     
     
         8 . A tree, characterized in that it
 (a) overexpresses an endogenous nucleic acid sequence, or   (b) expresses an exogenous nucleic acid sequence encoding cytokinin biosynthetic isopentenyl-transferase enzyme in cambial cells.   
     
     
         9 . The tree according to  claim 8 , wherein said tree expresses the genetic construct
 comprising a first nucleic acid sequence (effector) encoding cytokinin biosynthetic isopentenyl-transferase enzyme operable linked to a second nucleic acid sequence (promoter) allowing expression of said first nucleic acid sequence in cambial cells, said first nucleic acid sequence being selected from the group of
 a) a nucleic acid sequence comprising SEQ ID NO:1; 
 b) a nucleic acid sequence encoding SEQ ID NO:2; 
 c) a nucleic acid sequence encoding an amino acid sequence comprising a conserved domain area A, B and/or C having an amino acid sequence selected from the group of SEQ ID NO:3, 4 and 5, 
 d) a nucleic acid sequence encoding an amino acid sequence comprising an area D having at least 80% identity to amino acid sequence SEQ ID NO:6; 
 e) a nucleic acid sequence encoding an amino acid sequence showing at least 80% identity to SEQ ID NO: 2; and 
 f) a nucleic acid sequence encoding an enzyme belonging to enzyme class EC 2.5.1.27. 
   
     
     
         10 . The tree according to  claim 8 , wherein said tree expresses at least 40%, preferably at least 50% higher levels of cytokinin signaling in cambial cells during cambial development compared to WT tree. 
     
     
         11 . The tree according to  claim 8 , wherein the stem volume growth in said tree is at least 35% higher, preferably at least 40% higher compared to WT tree. 
     
     
         12 . The tree according to  claim 8 , wherein said tree belongs to angiosperms. 
     
     
         13 . The tree according to  claim 12 , wherein said tree is selected from the group of genera  Betula, Populus  and  Eucalyptus , preferably  Populus.    
     
     
         14 . The tree according to  claim 8 , wherein said tree belongs to gymnosperms. 
     
     
         15 . The tree according to  claim 14 , wherein said tree is selected from the group of spruce and pine. 
     
     
         16 . A wood product obtainable from the tree as defined in  claim 8 . 
     
     
         17 . A method for producing a transgenic plant capable of increased biomass production and/or increased stem volume growth compared to wild type plant, which comprises the steps of
 introducing a nucleic acid sequence encoding cytokinin biosynthetic isopentenyl-transferase enzyme operationally linked to a promoter allowing expression in cambial cells, to a tree cell,   cultivating said cell to form a cell culture,   regenerating the cell culture to a plant, in which the nucleic acid sequence encoding cytokinin biosynthetic isopentenyl-transferase enzyme is expressed in cambial cells during cambial development.   
     
     
         18 . A method for improving the production of biomass and/or increased stem volume growth in trees, which comprises the steps of
 introducing a nucleic acid sequence encoding cytokinin biosynthetic isopentenyl-transferase enzyme operationally linked to promoter allowing expression in cambial cells, to a tree cell,   cultivating said cell to form a cell culture,   regenerating the cell culture to a plant, in which the gene encoding cytokinin biosynthetic isopentenyl-transferase enzyme is expressed in cambial cells during cambial development,   allowing said plant to grow to an adult tree having enhanced radial growth compared to wild type tree.   
     
     
         19 . The genetic construct according to  claim 6 , wherein said  Populus  cambial specific promoter pLM5 is defined by SEQ ID NO:8.