Grain processing method and transgenic plants useful therein

Abstract

The invention provides novel methods of processing grain, such as corn and soybeans, utilizing thioredoxin and/or thioredoxin reductase to enhance extractability and recovery of starch and protein. The invention further provides novel transgenic plants expressing thermostable thioredoxin and/or thioredoxin reductase.

What is claimed is:  
     
         1 . A method for separating the starch and protein components of grain in a milling process, comprising: 
 (a) steeping the grain at an elevated temperature in the presence of supplemental thioredoxin, thioredoxin reductase, or both thioredoxin and thioredoxin reductase; and    (b) separating the starch and protein components of the grain.    
     
     
         2 . The method of  claim 1 , wherein the grain comprises grain from a transgenic plant that expresses one or both of thioredoxin and thioredoxin reductase.  
     
     
         3 . The method of  claim 2 , wherein the plant is corn.  
     
     
         4 . A transgenic plant comprising heterologous DNA coding for one or both of thermostable thioredoxin and thioredoxin reductase stably integrated into its nuclear or plastid genome.  
     
     
         5 . The plant of  claim 4  wherein the plant is corn or soybean.  
     
     
         6 . The plant of  claim 4  wherein the thioredoxin comprises SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, or SEQ ID NO: 5, and wherein the thioredoxin reductase comprises SEQ ID NO: 6 or SEQ ID NO: 7.  
     
     
         7 . A chimeric expression cassette comprising a coding region for a thermostable thioredoxin or thioredoxin reductase operatively linked to promoter and terminator sequences that function in a plant.  
     
     
         8 . The chimeric expression cassette of  claim 7  wherein the thioredoxin comprises SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, or SEQ ID NO: 5, and wherein the thioredoxin reductase comprises SEQ ID NO: 6 or SEQ ID NO: 7.  
     
     
         9 . A method of producing grain that expresses increased levels of thioredoxin and/or thioredoxin reductase comprising transforming plants with an expression cassette of  claim 7 .  
     
     
         10 . A method of producing grain that expresses increased levels of thioredoxin and/or thioredoxin reductase comprising transforming plants with an expression cassette of  claim 8 .  
     
     
         11 . A method of producing grain that expresses increased levels of thioredoxin or thioredoxin reductase, comprising: pollinating a first plant comprising a heterologous expression cassette comprising a transactivator-mediated promoter operatively linked to a DNA sequence coding for a thioredoxin or thioredoxin reductase with pollen from a second plant comprising a heterologous expression cassette comprising a promoter operatively linked to a DNA sequence coding for a transactivator capable of regulating said transactivator-mediated promoter; and recovering grain from the plant thus pollinated.  
     
     
         12 . An isolated nucleic acid molecule comprising SEQ ID NO: 24 or SEQ ID NO: 26.  
     
     
         13 . A chimeric gene comprising a promoter active in plants operatively linked to the nucleic acid molecule of  claim 12 .  
     
     
         14 . A recombinant vector comprising the chimeric gene of  claim 13 .  
     
     
         15 . A transgenic host cell comprising the chimeric gene of  claim 13 .  
     
     
         16 . A transgenic host cell according to  claim 15 , which is a transgenic plant cell.  
     
     
         17 . A transgenic plant comprising the transgenic plant cell of  claim 16 .  
     
     
         18 . The transgenic plant of  claim 17 , which is corn or soybean.  
     
     
         19 . Seed from a transgenic plant according to  claim 17.