Engineering Single-Gene-Controlled Staygreen Potential Into Plants

Abstract

The enzymes of the ACC synthase family are used in producing ethylene. Nucleotide and polypeptide sequences of ACC synthases are provided along with knockout plant cells having inhibition in expression and/or activity in an ACC synthase and knockout plants displaying a staygreen phenotype, a male sterility phenotype, or an inhibition in ethylene production. Methods for modulating staygreen potential in plants, methods for modulating sterility in plants, and methods for inhibiting ethylene production in plants are also provided.

What is claimed is: 
     
         1 . A method of increasing drought tolerance in a plant by modulating the ethylene pathway in the plant. 
     
     
         2 . The method of  claim 1  wherein said modulation is accomplished by reducing the ethylene production in a maize plant 
     
     
         3 . The method of  claim 2  wherein the reduction of ethylene production comprises downregulation of a gene encoding an enzyme involved in ethylene synthesis. 
     
     
         4 . The method of  claim 2  wherein said modulation is targeted to a specific tissue. 
     
     
         5 . The method of  claim 4  wherein said tissue is reproductive tissue. 
     
     
         6 . The method of  claim 1  wherein said plant is maize. 
     
     
         7 . A method of mediating maize response to water stress by modulating ethylene production in the maize plant, wherein the ethylene production is reduced by expressing a recombinant nucleic acid. 
     
     
         8 . The method of  claim 7  in which ethylene production in leaves is decreased. 
     
     
         9 . The method of  claim 7  in which leaf chlorophyll level of said maize plant under drought stress is higher than leaf chlorophyll level in a control maize plant under drought stress. 
     
     
         10 . The method of  claim 7  in which CO 2  assimilation of said maize plant under drought stress is higher than CO 2  assimilation in a control maize plant under drought stress. 
     
     
         11 . A method of increasing drought tolerance of a monocot crop plant, the method comprising modulating the production of ethylene in the crop plant, wherein the ethylene production is reduced by a genetic modification, and growing the monocot crop plant in a drought condition. 
     
     
         12 . The method of  claim 11 , wherein the genetic modification is RNA silencing. 
     
     
         13 . The method of  claim 11 , wherein the genetic modification is a mutation. 
     
     
         14 . The method of  claim 11 , wherein the monocot crop plant is maize. 
     
     
         15 . A method of maintaining or increasing photosynthetic activity of a monocot crop plant, the method comprising reducing the accumulation of ethylene in one or more tissues of the plant and growing the plant in a drought condition. 
     
     
         16 . The method of  claim 15 , wherein the ethylene accumulation is reduced by suppressing an ethylene biosynthesis enzyme. 
     
     
         17 . The method of  claim 15 , wherein the monocot crop plant is maize. 
     
     
         18 . The method of  claim 15 , wherein the photosynthetic activity is maintained under the drought condition through increased stomatal conductance. 
     
     
         19 . The method of  claim 15 , wherein the photosynthetic activity is maintained under the drought condition through increased CO 2  assimilation. 
     
     
         20 . The method of  claim 15 , wherein the photosynthetic activity is maintained under the drought condition through increased drought tolerance.