Compositions and methods of use of mitogen-activated protein kinase kinase kinase

Abstract

Methods and compositions for modulating plant response, development and yield under varying environmental conditions are provided. Methods employing MAPKKK are provided. The MAPKKK sequences are used in a variety of methods including modulating root development, modulating leaf and/or shoot development, modulating tolerance under abiotic stress and modulating yield. Transformed plants, plant cell, tissues, seed and expression vectors are also provided.

What is claimed is: 
     
         1 . An isolated mitogen-activated protein kinase kinase kinase (MAPKKK) polynucleotide selected from the group consisting of:
 (a) a polynucleotide that encodes the polypeptide of SEQ ID NO: 5;   (b) a polynucleotide comprising the sequence set forth in SEQ ID NO: 4;   (c) a polynucleotide encoding a polypeptide having at least 95% sequence identity to the entire length of SEQ ID NO: 5, wherein the sequence identity is determined by GAP Version 10 under default parameters; and   (d) an isolated polynucleotide degenerate from any of (a) to (c) as a result of the genetic code.   
     
     
         2 . A vector comprising at least one polynucleotide of  claim 1 . 
     
     
         3 . An isolated polypeptide with MAPKKK activity, selected from the group consisting of:
 (a) an isolated polypeptide comprising SEQ ID NO: 5;   (b) a polypeptide that is at least 95% identical to the amino acid sequence of SEQ ID NO: 5;   (c) a polypeptide that is encoded by a nucleic acid molecule comprising a nucleotide sequence that is at least 95% identical to the full length of SEQ ID NO: 4; and   (d) a fragment comprising at least 200 consecutive amino acids of SEQ ID NO: 5.   
     
     
         4 . A recombinant expression cassette comprising a polynucleotide operably linked to a promoter, wherein the polynucleotide encodes the polypeptide of  claim 3 . 
     
     
         5 . A transformed host cell comprising the isolated polypeptide of  claim 3 . 
     
     
         6 . The host cell of  claim 5 , wherein the host cell is a transformed plant cell. 
     
     
         7 . The plant cell of  claim 6 , wherein the plant cell is selected from the group consisting of sorghum, maize, rice, wheat, soybean, sunflower, canola, alfalfa, barley and millet. 
     
     
         8 . A transformed plant regenerated from the plant cell of  claim 6 . 
     
     
         9 . A transformed seed of the plant of  claim 8 . 
     
     
         10 . A method for increasing abiotic stress tolerance in a plant, said method comprising the steps of:
 (a) introducing into a plant cell a construct comprising a polynucleotide encoding a mitogen-activated protein kinase kinase kinase (MAPKKK), wherein said polynucleotide is operably linked to a promoter functional in plant cells, and wherein the polynucleotide is selected from the group consisting of:
 (1) a polynucleotide that encodes the polypeptide of SEQ ID NO: 5; 
 (2) a polynucleotide comprising the sequence set forth in SEQ ID NO: 4; 
 (3) a polynucleotide having at least 95% sequence identity to SEQ ID NO: 4, wherein the % sequence identity is based on the entire coding region and is determined by GAP Version 10 under default parameters; 
 (4) an isolated polynucleotide degenerate from any of (1) to (3) as a result of the genetic code; 
 (5) a polynucleotide complementary to a polynucleotide of any one of (1) to (4); 
   (b) regenerating a transgenic plant from said transformed plant cell, wherein said MAPKKK is expressed in at least some cells of said transgenic plant at levels sufficient to increase abiotic stress tolerance in said transgenic plant, relative to a control.   
     
     
         11 . The method of  claim 10 , wherein said abiotic stress comprises low temperature, frost, freeze, salt, osmotic stress, drought, high temperature, chemical stress, environmental stress or other stress involving oxidative stress damage. 
     
     
         12 . The method of  claim 10 , wherein the MAPKKK protein activates or increases the expression of a stress-inducible gene. 
     
     
         13 . The method of  claim 12 , wherein the stress-inducible gene comprises ZmMAP kinase 4(MPK4) or ZmMAP kinase 5(MPK5). 
     
     
         14 . The method of  claim 12 , wherein the stress-inducible gene is operably linked to a glutathione S-transferase promoter, an ASI promoter or a heat shock promoter. 
     
     
         15 . The method of  claim 10 , wherein said polynucleotide encoding the MAPKKK is constitutively expressed. 
     
     
         16 . The method of  claim 10 , wherein said polynucleotide encoding the MAPKKK is inducibly expressed. 
     
     
         17 . The method of  claim 10 , wherein said polynucleotide encoding the MAPKKK is expressed in a cell-specific, tissue-specific or organ-specific manner. 
     
     
         18 . The method of  claim 10 , wherein the plant is a dicotyledonous plant. 
     
     
         19 . The method of  claim 10 , wherein the plant is a monocotyledonous plant.